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Title: Saguaro National Monument, Arizona
Author: Shelton, Napier
Language: English
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*** Start of this LibraryBlog Digital Book "Saguaro National Monument, Arizona" ***
[Illustration: Saguaro cactus]
saguaro
national
monument
ARIZONA
Napier Shelton
_based on an earlier work by Natt Dodge_
NATURAL HISTORY SERIES
1972
National Park Service
U.S. DEPARTMENT of the INTERIOR
For sale by the Superintendent of Documents, U.S. Government Printing
Office
Washington, D.C. 20402—Price $1.25
Stock Number 2405-0292
preface
This book is a simple account of the natural history of Saguaro National
Monument. It is intended to help you understand the relationships
between land, climate, plants, wild animals, and man in the environment
of a hot desert. While it includes brief profiles of many representative
species, it is not intended to serve as a guide to the monument. It does
indicate where the several distinctive natural communities exist, and
when and where to look for certain plants and animals. For
identification purposes, you will need field guides.
The present edition is my revision of the 1957 book by Natt Dodge, then
naturalist for the Southwest Region of the National Park Service. The
first five and the last two chapters are essentially new; the central
chapters on plants and animals remain largely as written in the first
edition.
The authors wish to thank former and present members of the monument
staff for their help and companionship, in both field and office. We are
particularly grateful to Chief Naturalist Harold T. Coss, Jr., who
devoted much time and effort to obtaining many of the photographs and,
with Park Biologist Warren F. Steenbergh, gave the manuscript a thorough
scrutiny. The cooperation and hospitality of Superintendent Harold R.
Jones have created the best possible climate for work on the revised
edition. National Park Service geologist Robert H. Rose contributed in
very great measure to the geological content. Finally, our thanks go to
the many students of desert life on whose knowledge this book has been
built, and to monument visitors who ask questions—for their concern
gives hope for better relations between man and nature.
—N.S.
contents
The Desert Scene, 1
The Sonoran Desert and the Monument, 3
Climate: The Vital Factor, 9
Rocks: Foundation and Soilmakers, 13
Plant and Animal Zones, 19
Desert Plants, 23
Succulents, 25
The Saguaro—Monarch of the Monument, 27
Other Common Cactuses, 33
Non-Succulents, 36
Perennials, 36
Ephemerals, 42
Major Plant Communities of Saguaro, 49
Plants of the Hills and Mountains, 55
Oak-Pine Woodland, 55
Ponderosa Pine Forest, 58
Animals and How They Survive, 61
Invertebrates, 62
Amphibians, 64
Reptiles, 64
Birds, 66
Mammals, 72
The Rhythms of Nature, 79
The Impact of Man, 83
Appendix, 87
Suggested Reading, 87
Common and Scientific Names of Plants, 89
Reptiles and Amphibians of the monument, 92
Birds of the monument, 94
Mammals of the monument, 97
[Illustration: Brittlebush display along Cactus Forest Drive.]
the desert scene
Scattered through the wide, lonely Sonoran Desert, isolated mountain
ranges raise jagged blue silhouettes against the sky. The high ones wear
a crown of dark pines and a speckled mantle of oaks. Lapping against
their feet is the desert sea, studded with the green masts of giant
saguaro cactuses rising above a motley crew of tough, strange, often
handsome subordinates.
On either side of the Santa Cruz Valley in southeastern Arizona, Saguaro
National Monument embraces two of these ranges, with the desert lands at
their feet. Although it was established primarily to preserve impressive
stands of saguaros, it gains wholeness by including the mountains that
shed the rocky soil on which the saguaros grow. The monument is in two
sections, some 30 miles apart. The _Rincon Mountain Section_, east of
Tucson, includes in its 99 square miles a spectrum of plantlife ranging
from saguaro communities at the low elevations to a wet fir forest on
the north slope of 8,666-foot Mica Mountain. The 24-square-mile _Tucson
Mountain Section_, about 12 miles west of the city, has a denser stand
of saguaros, on the lower slopes of a wild jumble of volcanic mountains
dominated by 4,687-foot Wasson Peak.
Within the cactus forests and upon the mountain slopes, life in myriad
forms goes on in a delicate and continuous adjustment to changing
environments. Over millennia, mountains rise and crumble, species evolve
and fade from the scene. Over days and weeks and years, populations of
plants and animals rise and fall, in response to thousands of
interactions which we are only beginning to understand. In the following
pages, we will meet the main characters in this natural drama (including
some of the most improbable in all of nature); we will investigate the
environmental stage upon which they perform; and we will try to
understand something of the play itself, including our own role in it.
[Illustration: The Saguaro Forest in the Tucson Mountain Section.]
the sonoran desert
and the monument
Saguaro National Monument is at the northeastern edge of the Sonoran
Desert. Named for the state of Sonora, Mexico, in which the greater part
of it lies, this, one of four major deserts in North America, is
distinguished by differences in climate and vegetation. The Great Basin
Desert, mainly in Nevada and Utah between the Rockies and the Sierra
Nevada, has cold winters, sparse precipitation distributed fairly evenly
throughout the year, and rather simple vegetation dominated by the low
shrubs, sagebrush and saltbrush. Immediately to the south, in southern
Nevada and southeastern California, is the Mohave Desert, with cool
winters during which most of the year’s precipitation comes, and with
plant cover consisting mostly of shrubs such as creosotebush. At higher
elevations grows the Joshua-tree, a giant yucca. The Chihuahuan Desert,
with cool winters and summer rainfall, covers the broad plateau of
north-central Mexico, extending into southern New Mexico and west Texas.
Its vegetation consists mostly of small cactuses, spiny shrubs, and
succulent-leaved plants such as yuccas.
Lying between the Mohave and Chihuahuan deserts, the Sonoran Desert has
both winter and summer rainfall, with spring and autumn droughts. Its
mild winters and bi-seasonal rainfall encourage a vegetation far
surpassing in lushness and variety that of the other deserts. From west
to east, the land rises and precipitation increases. Yuma, in
southwestern Arizona, lying at 141 feet above sea level, gets about 3
inches a year. Tucson, in southeastern Arizona, is at 2,400 feet
elevation and averages 11 inches a year. In the western part, where
plains are extensive and mountain ranges low and far apart, a very few
small-leaved species such as creosotebush dominate. Toward the east,
mountain ranges become more numerous, shedding material on which more
kinds of plants, particularly paloverde, mesquite, and cactuses, assume
leading roles in the vegetative cover. Both sections of the monument lie
within the eastern, wetter, more diversified part of the Sonoran Desert
known as the Arizona Upland. Organ Pipe Cactus National Monument, to the
southwest, is in an area transitional between the Arizona upland and
Colorado River lowland phases of the Sonoran Desert.
[Illustration: DESERT AREAS OF NORTH AMERICA]
But even between the two sections of Saguaro National Monument there are
differences. There is the obvious fact that the Tucson Mountains are
much lower and smaller in mass than the Rincons. And there is the
not-so-obvious fact that the Tucson Mountain Section extends to lower
elevations (2,200 as opposed to 2,700 feet). These conditions are
reflected in the somewhat warmer environment of the western section.
This helps to explain why certain Sonoran Desert plants and animals here
reach their northeastern limits; among them are ironwood, desert iguana,
desert horned lizard, western shovel-nosed snake, sidewinder, desert
kangaroo rat, and the Le Conte thrasher. The Rincon Mountain Section, by
virtue of its higher elevations, has plants and animals—such as
ponderosa pine, Steller’s jay, and whitetail deer—not found in the
western section.
On the geologic time scale the Sonoran Desert, like all the earth’s
present deserts, is a recent development. Some 50 million years ago
tropical forests grew here, as they did over most of southern North
America. As the Southwest gradually became drier, new species adapted to
the new conditions evolved; and the general type of vegetation
changed—with some retrogression during wetter periods—from forest to
savanna (grasslands with scattered trees) to arid subtropical scrub
(such as is now found in southern Sonora State), and finally to the
plant communities of today’s Sonoran Desert. The last stage has occurred
only during the past few million years.
The assemblage of species from which most of our present desert and
lower mountain plants were derived is known as the Madro-Tertiary Flora,
to denote its center (Sierra Madre in Mexico) and time (Tertiary
period—one million to 65 million years ago) of early development.
Reflecting these origins, a majority of the species growing below 6,000
feet elevation in the monument today are basically Mexican or Central or
South American in their distribution.
On the higher mountains of the Sonoran Desert, however, exist species
with an entirely different ancestry. Most of the plants of the pine and
fir forests of these high places, like the plants of the Great Basin
Desert, derive from the Arcto-Tertiary Flora, which dominated the
northern part of our continent during Tertiary times. As climate
changes, one or the other of these great plant assemblages will benefit
at the expense of the other. If cooler, wetter periods return, as they
did during the Pleistocene epoch, ponderosa pines, now found above 6,000
feet, may again grow nearly as low down as today’s cactus forests. But
if the present long-term drying trend continues, the northern plants
will eventually be squeezed off their mountaintops.
Animals, to some extent, reflect the same dichotomy of origins we have
seen in the plants. Thus, on the mountaintops supporting pine and fir
forests, a northern contingent of animals predominates, while on the
lower slopes and desert the fauna has a Mexican character. The canyons
and oak-pine forests of middle elevations in southeastern Arizona are
particularly exciting, because in these biological islands, isolated by
surrounding desert, live many “Mexican” species of animals found nowhere
else in the United States. Naturally, mountain ranges nearest the
border—such as the Huachucas and Chiricahuas—have the greatest numbers
of Mexican specialties; but the Rincons have their share too.
The wonderful diversity of plant and animal life in Saguaro National
Monument depends on a diversity of habitats. These in turn owe their
existence to a widely varying triumvirate of environmental
factors—climate, soil, and topography. To understand the biological
interplay that goes on here, we first must know something of the
environmental conditions that circumscribe it.
[Illustration: Plant communities on Mica Mountain.]
Geological Time Table
Era Period Epoch Years Major
before geological
present events
time
Cenozoic Quaternary Recent 10,000 Cascade Range
and Sierra
Nevada uplifted
Pleistocene
1,000,000
Tertiary Pliocene
12,000,000
Miocene
26,000,000
Oligocene
38,000,000
Eocene
54,000,000 Rocky Mountains
formed
Paleocene
65,000,000
Mesozoic Cretaceous
136,000,000
Jurassic
195,000,000
Triassic
250,000,000 Appalachian
folding
Paleozoic Permian
280,000,000
Pennsylvanian
320,000,000
Mississippian
345,000,000
Devonian
395,000,000
Silurian
440,000,000
Ordovician
500,000,000
Cambrian
570,000,000
Precambrian
[Illustration: Summer thunderstorm in the Rincon Mountain Section.
The Catalina Mountains rise in the background.]
climate:
the vital factor
Climate is the chief arbiter of life on earth. Each plant and animal,
including man, has tolerance limits for heat and water below or above
which it dies. The Sonoran desert, with its low and uncertain rainfall
and high summer temperatures, thus presents one of earth’s most taxing
environments. For most desert plants and animals, the main problem
presented by this climatic combination is a scarcity of water. Why, we
might ask, is this part of the globe so dry?
Essentially, the dryness of the Sonoran and other southwestern deserts
results from their geographic situation. First, these lands lie east of
a persistent high-pressure cell over the eastern Pacific—part of a belt
of high-pressure cells which encircles the earth at this latitude.
High-pressure systems in the Northern Hemisphere have descending,
warming, dry air in their middles and along their eastern sides. The air
that flows eastward from the “East Pacific high” thus contains little
moisture, and dictates desert conditions over much of the Southwest.
Furthermore, the mountains that more or less ring these deserts
intercept much of the meager incoming moisture, by forcing the air to
rise and cool so that its moisture condenses and falls to the ground.
But during two periods of the year, the desert does receive rain. In
winter, the East Pacific high shifts southward with the sun, reducing
its effects on the Southwest. Now the low pressure storm systems, which
at this season move eastward across the continent, can sometimes dip far
enough south to bring rain to the Sonoran Desert. These rains are
usually gentle, and cover large areas. Their clouds may cover the sky
for several days at a time.
By April, the East Pacific high has returned far enough northward to
resume its control of southwestern weather. Now the fore-summer drought
sets in, intensified by gradually rising temperatures. Day after day the
sun climbs higher in the sky, baking the earth and testing the endurance
of desert life. Then, sometime in late June or early July, clouds begin
forming in the afternoons over the mountains; finally, one day they
build up to great thunderheads. The drought ends suddenly as rain pours
down and lightning cracks the sky. Down the canyons and along the desert
washes rages the water, brown with soil. In a short time, the storm is
over, and the water disappears into the ground. Just 1 mile away, rain
may not have fallen.
These intense, local summer rains, so different from the winter ones,
have a different origin as well. They are spawned by the Atlantic’s
Bermuda high, which has shifted northwestward and sent moist air from
the Atlantic and Gulf of Mexico flowing off its western edge toward the
deserts. This air rises quickly when it strikes hot, high mountains such
as the Rincons, and its moisture condenses to fall as rain.
Some time in September the rains of summer stop, as the Bermuda High
moves south again, removing its influence and returning the East Pacific
high to a position of dominance. The sun and wind again wring moisture
from the soil, but with diminishing effect. The thermometer no longer
reaches the 100’s as it did in June, July, and August. In November or
December, the winter rains begin. Water stays longer in the soil,
because temperatures now range between 30° and 80°. Life in the desert
begins a new cycle. This rainy period usually lasts into March.
On the mountain slopes, of course, the same seasonal patterns of heat
and precipitation occur, but they are tempered or enhanced by elevation.
With increasing elevation, temperatures decline and precipitation
increases. When July temperatures at headquarters are averaging in the
nineties, they will be in the sixties on top of the Rincons. In the
cactus forest at the foot of Tanque Verde Ridge only about 10 to 12
inches of rain fall in a year, while Manning Camp, at 8,000 feet, gets
about 18 to 25 inches. These up-slope gradients of temperature and
precipitation, as we shall see, have pronounced effects on plant and
animal life.
[Illustration: Gila monster.]
[Illustration: Banded augen gneiss on Cactus Forest Drive. Javelinas
formerly took refuge from the sun in the dens under these
overhanging rocks.]
rocks:
foundation and soilmakers
Soils are derived from the fragmentation and decomposition of rocks.
Combinations of soils and climate, varying from place to place, create
an almost infinite number of environments with differences so subtle and
small as to make it appropriate to refer to them as microenvironments.
Though these differences be minor, they are often sufficient to create
niches each of which becomes a habitat for a particular group of plants
and animals. Thus it is that the saguaros and other desert vegetation in
Saguaro National Monument and vicinity are found in particular
environmental or ecological niches where just the right combinations of
soils, moisture, sunlight, temperature and other factors are present.
Since the rocks provide the foundation and the source of soils that
support the plant and animal life, it is helpful to understand something
about the origin and evolution of the rocks and the landscape of which
they are a part. Clues to this story are to be found in the composition
of the rocks and their relationships to one another.
Rocks of the three major classes—igneous, metamorphic, and
sedimentary—are found within the monument. The igneous rocks include
granites and various kinds of lava flows, together with some intrusive
dikes and veins. The metamorphic rocks are represented by gneiss and
schist. Lastly, sedimentary rocks occur as limestone, sandstone, and
alluvial fill material. Each of these great classes of rocks was formed
in a different manner, and these differences reveal the nature of the
events which are a part of the geologic history of the monument and
surrounding area.
Catalina Gneiss (pronounced NICE) is the predominant rock that visitors
see in the Rincon Mountains and the Tanque Verde Ridge; exposures of
granite and schist are also found. Gneiss is a coarse-grained
metamorphic rock resembling granite, having a banded appearance, and
consisting of alternating layers of different minerals such as feldspar,
quartz, mica, and hornblende. The banding and texture reveal that the
gneiss, now exposed by uplift and erosion, was formed from parent rocks
deep below the earth’s surface during the Precambrian Era more than a
half billion years ago. There the parent rocks, subjected to pressure
and heat, melted, flowed, and crystallized, before resolidification.
Though the gneiss of the Rincon Mountains is ancient, the uplift that
raised it to its present height is thought to have occurred rather
recently (within the past 24 million years), during the period when most
of the Sonoran Desert ranges apparently were formed. In age, these
mountains thus would fall somewhere between the older Rockies and the
younger Sierra Nevada.
The schist, which underlies much of the Cactus Forest, where it is
exposed along washes, was probably formed during the Cretaceous period
more than 65 million years ago. Like the gneiss, the schist is a
metamorphic rock, having been formed by the transformation of parent
rocks at depth under great pressure and heat. Due mainly to differences
in the composition of the parent rock, together with its mica content,
the rock that resulted was platy and cleavable (accounting for its
classification as schist).
Granite, which forms Wasson and Amole peaks in the Tucson Mountain
Section, is an igneous rock that (like the metamorphic gneiss and
schist) originated at depths below the earth’s surface. The granite was
formed by the solidification of molten rock material that moved upward
en masse from greater depths, rather than by the alteration of ancestral
rocks. Erosion of the uplifted land mass has not only stripped away the
overburden but has developed valleys deeply incised into the granite
itself.
Volcanic rocks in the form of rhyolite, andesite, and basalt flows also
are exposed, chiefly in the Tucson Mountain section of the monument.
These are all extrusive igneous rocks composed of magma that solidified
after reaching the earth’s surface through vents or fissures. There are
differences in the lava flows, reflecting differences in composition,
temperature, and other conditions of the magma from which they were
formed. The rhyolite is lighter in color than andesite, and it is
somewhat richer in feldspar. Basalt, on the other hand, is dark, is
deficient in feldspar and quartz, and contains relatively large amounts
of the darker minerals such as hornblende, pyroxene, and olivene. Lava
flows of the rhyolite and andesite variety occur in the Cactus Forest
locality of the Rincon Mountain Section. Cat Mountain Rhyolite is the
name given to a rhyolite flow of Tertiary age that forms the topmost
layer in much of the Tucson Mountain Section. A small exposure of basalt
is also found here.
Limestone, sandstone, and shale formations are also exposed at various
places within the monument. They are reliable indicators of seas that
covered the area during one or more times of the geologic past.
Comparisons with the limestone formations farther to the south in the
Colossal Cave region indicate that the limestone in the monument was
formed as far back as late in the Paleozoic Era (345 million years or
more ago). This age is suggested by types of fossils, including
fragments of crablike trilobites and crinoid (sea lily) stems, found in
limestones of the same age near Colossal Cave.
The Recreation Redbeds of the Tucson Mountain Section is one of the
important sandstone members exposed in the monument. Geologists believe
that its deposition occurred early in the Cretaceous Period more than 65
million years ago. Above the Recreation Redbeds lies a formation
consisting mainly of limestone and commonly known as the Tucson Mountain
“Chaos”—an appropriate name, in view of the geologists’ meager knowledge
of it. Within the Chaos formation, believed to be lower to Middle
Tertiary in age, are limestone blocks of greater age than the rocks
within which they are entombed. No generally accepted explanations have
been advanced as to how these relationships developed.
The processes that destroy mountains continue concurrently with those
that build them. Temperature changes, weathering, and downslope creep
under the influence of gravity are among the agents which destroy the
rocks and eventually convert them into soil. Though these processes work
rapidly from a geological standpoint, in terms of the average human life
span, they progress at an imperceptible rate. Violent thunderstorms and
cloudbursts, however, cause a massive, often spectacular movement of
boulders, gravel, sand, and silt by torrential streams.
In desert regions, most of the runoff from storms sinks into the slopes,
dropping its burden along the way. Big rocks are dropped early as the
carrying power of the water diminishes with the speed of flow; smaller
fragments travel farther. The finest material is carried far out into
the basins between mountain ranges, gradually filling them. (The
alluvial material in the Tucson Basin is estimated to be 2,000 to 5,000
feet thick.) Thus desert mountains tend to bury themselves in their own
debris.
Alluvial fans (fan-shaped deposits built by rivers flowing from
mountains into lowlands) form at the mouths of canyons. Sometimes the
alluvial fans of adjacent canyons coalesce, forming the long, sweeping
slope known as a bajada (pronounced ba-HA-da). In other places the
eroded bedrock extends outward from the bases of desert mountains,
forming “pediments,” which are usually covered by a veneer of alluvial
material. Pediments of this kind stretch from the lower slopes of the
Rincon Mountains. In the Tucson Mountains the alluvial material deepens
rapidly toward the Avra Valley because the bedrock at the base of the
mountain dips steeply downward.
Serious gaps remain in the story of the origin and evolution of the
landscape in Saguaro National Monument. Moreover, it is difficult to
establish the exact sequence in which the various events occurred. The
composition, texture, and relationships of the rocks, however, do reveal
much about the nature of the events and the processes that were
involved.
[Illustration: During summer, mule deer and javelina frequent King
Canyon, which has the only known permanent spring in the Tucson
Mountains. The predominant rock in this major canyon northeast of
the Arizona-Sonora Desert Museum is called Amole Arkose; it is of
sedimentary origin and was deposited during the Cretaceous period.]
[Illustration: GEOLOGICAL CROSS-SECTION OF SANTA CRUZ VALLEY]
Faults are hypothetical
Showing:
Valley Fill
Wasson Peak
_Granite_
_Folded and tilted Sedimentary and Volcanic Rock_
_Santa Cruz River_
_Flood Plain_
_Valley Fill_
Tucson
_Pantano Wash_
Pediment
Tanque Verde Ridge
Mica Mountain
_Gneiss_
The presence of the limestones and sandstones indicates that that area
was submerged below the water of ancient seas one or more times in the
geologic past. The gneiss, schist, and granite bespeak deep-seated
metamorphism and magmatic intrusion, which gave these rocks the form,
composition, and texture they possess today. The lava flows are
indicative of volcanic activity that was a part of the extensive
volcanism that occurred in this part of southern Arizona. And, finally,
the great alluvial fans and bajadas suggest that these mountain ranges
could bury themselves in their own products of erosion unless the
mountain-building processes in future eons continue at a faster pace
than the wearing-down processes. This evidence enables us to perceive
today’s landscape as but a transitional phase in the drama of change
that will continue for milleniums.
[Illustration: Chiminea Creek, originating in the higher elevations
of the Rincon Mountains, forms a ribbonlike oasis of hydrophytic
plants, including large trees such as sycamore, walnut, and
cottonwood.]
plant and animal zones
Mountains are biologically exciting because their elevation produces, in
a short vertical distance, the same climatic changes that occur over
long latitudinal distances. In Arizona, average temperatures drop about
4° with each 1,000-foot rise in elevation, and precipitation increases
about 4 to 5 inches. At sea level, you would have to travel about 900
miles north to experience the climatic change found in going from the
lowest part of the monument (2,200 feet) to the top of Mica Mountain
(8,600 feet). Plant-and-animal communities change along these climatic
gradients.
In southern Arizona, the sequence of vegetation types begins with desert
scrub at the lowest elevations, and ranges through desert grassland, oak
woodland and chaparral, oak-pine woodland, ponderosa pine forest, and
Douglas-fir forest, to Engelmann spruce forest on top of the highest
mountains. In the national monument, we have all these types except the
last—although desert grassland is poorly represented here because the
steep slopes squeeze it into a narrow altitudinal band; and Douglas-fir
forest is restricted to small areas in canyons and on north-facing
slopes at high elevations. A few drainageways (notably Chiminea Canyon,
on the south side of the monument) support patches of deciduous trees
classified as riparian woodland.
These vegetation zones should not be visualized as nice neat bands on
the mountainsides, however, for roughness of topography and differing
tolerances of plant species usually lead to gradual changes from one
zone to the next. Because of the greater exposure to drying heat and
sunlight, each belt occupies a higher range of elevation on south-facing
slopes than on north-facing ones. And along draws, where conditions are
wetter and cooler than on ridges at the same elevations, the vegetation
zones finger down to lower elevations; on ridges the opposite is true.
Animals are less restricted than plants to particular vegetation belts,
but they, too, show a zonation with altitude. You must look, for
instance, in the paloverde-saguaro community (part of the desert scrub
type) for kangaroo rats and cactus wrens; in the oak-pine woodland for
Mexican jays; and in the ponderosa pine forest for whitetail deer and
tassel-eared squirrels.
In the Tucson Mountains, only the desert scrub type is well represented,
although the highest ridges support a suggestion of desert grassland. A
small patch of shrub live oaks, relicts of a wetter period, huddles on
the north side of Wasson Peak. Zonation is poorly developed here because
the mountains are low and small in mass. (Studies have shown that
mountains of smaller mass tend to have warmer and drier climates than
bulkier mountains of the same height.)
Major Vegetation Types in Saguaro National Monument
Vegetation type Average Elevations Annual Life zone
July (feet) rainfall
temp. (inches)
Prominent species
Southwestern Desert 94 2,200 to 4,000 7 to 13 Lower Sonoran
Scrub
Paloverde
Saguaro
Pricklypear
Cholla
Catclaw
Ocotillo
Creosotebush
Mesquite
Ironwood[1]
Grassland Transition 85 3,500 to 4,500 10 to 15 Upper Sonoran
Mesquite
Beargrass
Gramagrasses
Amole
Sotol
Oak-pine-juniper 74 4,500 to 7,000 12 to 22 Upper Sonoran
Woodland and
Chaparral
Emory Oak
Mexican Blue Oak
Shrub Live Oak
Pinyon Pine
Mountain-mahogany
Manzanita
Skunkbush
Coniferous Forest 68 above 6,000 18 to 30 Transition and
start of Canadian
Ponderosa Pine
Gambel Oak
Buckbrush
Mountain Muhly
Douglas-fir
White Fir
Aspen
Snowberry
Mexican White Pine
[1]TUCSON MOUNTAIN SECTION
Biologists have developed several systems for classifying assemblages of
plants and animals over broad regions, and one of the most widely known
is that of C. Hart Merriam. Around the turn of the century, he conceived
a system of “life zones,” named for the parts of the continent where
they are best developed: Tropical, Lower Sonoran, Upper Sonoran,
Transition, Canadian, Hudsonian, and Arctic. In Saguaro National
Monument, the Lower Sonoran Zone corresponds to the desert scrub type;
the Upper Sonoran includes desert grassland transition, oak woodland,
and oak-pine woodland; the Transition Zone is equivalent to the
ponderosa pine forest; and the poorly represented Canadian Zone has
Douglas-fir and white fir. Because Merriam’s system is so widely used,
his terms are included in the tabulation on page 20, which summarizes
the main characteristics of plant zones in the monument.
The best way to appreciate the biotic changes that occur with elevation
is to walk or ride a horse to the top of the Rincons. But if your time
or energy is limited you can get a quick view of these sequences by
driving up nearby Mount Lemmon, in the Santa Catalina Mountains.
[Illustration: Saguaro Forest landscape from the scenic drive.]
desert plants
When you look out over the cactus forest, in either part of Saguaro
National Monument, you may think there’s a sameness to it in all
directions—saguaros standing amid scattered shrubs. But look harder, or
walk about, and you will discover variations in the scene. First, there
is a gradual change in the vegetation from the mountain foot down the
bajada or pediment to the valley floor, as saguaros and paloverdes
(green) become sparser and creosotebushes (smaller and brownish) take
over. (The monument itself does not extend far enough from the mountain
bases to include extensive creosotebush communities, but these cover
large areas in the lowest parts of the valleys.) Then there is the
luxuriant growth along washes, where mesquites and paloverdes grow to
tree size and there are more kinds of plants. And if you are observant
you may notice slight variations with each change in slope on the
rolling hills—for example, more grass growing on their north sides. On
another scale, you can see separate little communities of plants in
special situations, as under shrubs or on rocks.
These patterns are due to variations in the environment. For the desert
is hotter and drier in some places than in others. The gradual downslope
changes in vegetation reflect the decrease in the amount of soil
moisture available to plants—a condition caused by the decreasing size
of soil particles and consequent shrinkage of water-holding space
between particles. Desert washes encourage plant growth because they
channel water and cold air. Strangely enough, night temperatures are
often lower in a desert valley than farther up the slopes. This
“inversion” is due to drainage of cold air down mountainsides, forming
cold “pools” in valley bottoms, especially in winter. Cold air is
heavier than warm, and (since air flows much like water) it is channeled
down the draws—a fact that will strike you if you walk into a wash near
the mountains at night or early in the morning. Add this phenomenon to
the great amounts of moisture that lie beneath the surface of washes,
and you can see that desert drainageways are really linear oases. More
subtly, desert hills reflect in their vegetation the differences in soil
moisture from north slopes to south slopes caused by increasing exposure
to sunlight.
[Illustration: Saguaro cactus]
One controlling factor, then, is dominant in the desert: the scarcity of
water. This results not only in the unusual forms and adaptations of
desert plants, but also in a distinctive type of plant community. In
wetter climes, plants compete mostly for sunlight. They can grow close
together, as long as they receive adequate illumination. During the
regrowth of forests, several distinct sets of plants appear, each
succeeding group more tolerant of shade than the last, as the forest
canopy closes. In the desert, there is no such succession. Clear a patch
of desert vegetation, and the same species will reappear—spaced out,
with bare ground between them as before. For here sunlight is abundant
(we might say overabundant), but there is not enough water to allow
plants to cover the ground.
Dr. Forrest Shreve, who was a botanist at the Carnegie Institution’s
Desert Laboratory near Tucson and a master student of deserts, defined a
desert as “an area in which deficient and uncertain rainfall ... has
made a strong impression on the structure, functions, and behavior of
living things.” The distinctive characteristics of desert plants and
animals have evolved through millions of years, in a trial-and-error
process in which only the better-fitted forms have survived. It would be
enlightening to know how many of the species and varieties of plants
that developed during the past 60 million years or so have failed to
adapt to Sonoran Desert conditions. It is fascinating to study the
hundreds of forms that have succeeded and to try to determine what
structures they have perfected and what methods they have originated
that enabled them to maintain themselves in such a harsh environment.
Desert plants can be classified as “escapers,” “evaders,” and
“resisters,” according to their means of adaptation to water shortage.
Escapers, such as the annuals, avoid the problem entirely by waiting out
the dry periods as seeds, to sprout and reproduce only when the rains
come. Evaders, such as the ocotillo, reduce their water loss during
droughts by such methods as dropping their leaves or going into a state
of dormancy. Resisters, however, “hang in there” all year, taking the
desert’s worst. The cactuses, prime examples of this group, rapidly soak
up water from each rain and store it for use during drought; the
mesquite’s deep roots tap a more constant source of moisture.
Succulents
A large group of desert plants conserve water for use in periods of
drought by storing it in specialized tissues during the wet season. Some
of these “succulents,” principally the yuccas, eschevarias, and agaves,
have developed water-storage tissues in their leaves. A few, notably the
NIGHTBLOOMING CEREUS (see appendix for scientific names of plants), have
slender stems but an enormous, carrot-shaped root in which the
moisture-storage tissue is located. The GOURDS also have large, thick,
moisture-retaining roots, as does the WILD-CUCUMBER.
The cactuses store water in their stems and thus are called stem
succulents. In the course of its evolution the cactus has eliminated
leaves, and their function has been taken over by the green outer
covering of the stems. Thus the amount of transpiration (moisture loss
through plant breathing pores) has been greatly reduced.
[Illustration: Saguaro buds.]
The cactuses are thought to have evolved from relatives of the rose
family in the West Indies, beginning some 18,000 to 20,000 years ago.
From there they spread to most parts of the Western Hemisphere, but
particularly to the drier regions, changing their forms to meet new
conditions. One of the youngest of plant families, the cactuses are
still evolving rapidly. This doesn’t make the task of classifying them
easier for the taxonomists.
In varied forms, cactuses enliven the paloverde-saguaro community. In
size they range from tiny button and pincushion types, some of which
weigh only a few ounces, to the giant saguaro, the bulkiest of which may
weigh several tons.
Cactuses as a group are easily recognized, although many people
mistakenly believe that any desert plant with spines or thorns is a
cactus. Shreve describes their main characteristics thus:
Several structural features have served to give the cacti their
outstanding appearance, so unlike that of other plants. Most general
have been the loss of the leaf as a permanent organ, the enlargement
of the stem to accommodate water-storing tissue, and the development
of local spinebearing structures known as “areoles.” In several
genera, the stem is segmented into sections which are flat and
somewhat leaflike; in others the stem is round, much branched, and the
surface occupied by close-set tubercles. In a large group, including
massive erect forms, as well as slender climbing ones, the stem is
grooved or fluted and thus able readily to accommodate its surface to
great fluctuations in the water content of the tissues.
If you are trying to identify species, however, cactuses can be
annoying, since they often hybridize. You must expect to find some
individuals that don’t fit the book descriptions.
_The Saguaro—Monarch of the Monument_
Of all the species of cactus recorded in Saguaro National Monument, the
giant SAGUARO (pronounced sah-WAH-roe) holds the center of interest.
From the visitor’s standpoint, all other plants, no matter how bizarre
in appearance or peculiar in living habits, are merely stage scenery for
setting off the star of the desert drama. For size, this vegetable
mammoth tops all other succulents of this country; heights of more than
50 feet and weights of more than 5 tons have been reported. There have
been specimens with more than 50 arms, or branches. Although no accurate
method of determining saguaro age has been devised, it is estimated that
an occasional veteran may reach the two-century mark.
Structurally, the giant cactus is well adapted to meet the stern
requirements of its habitat. Its widespread root system, as much as 70
feet in diameter, lying close to the surface of the ground, anchors and
holds the heavy plant erect. The shallow root system quickly and
efficiently collects and channels to the main stem any moisture that may
penetrate the topsoil. The trunk and branches have a cylindrical
framework of long slender poles or ribs fused at the constricted base.
This woody skeleton supports the mass of pulpy tissue, the whole being
covered with tough, waxy, spine-bearing “skin.” Numerous vertical
ridges, like the pleats of a huge accordion, permit the stems and
branches to expand in girth as the tissues swell with water during wet
weather and to shrink during times of drought.
So efficient is the saguaro’s water-storage system that, even after
years of extreme drought, the plant retains enough moisture in reserve
to enable it to produce flower buds. The buds appear in vertical rows at
the tips of the main stem and branches, a few opening each evening over
a period of several weeks in May and June. The flowers, up to 4 inches
in diameter, have waxy white petals. This beautiful blossom is the State
flower of Arizona. The egg-shaped fruits mature in late June and July,
splitting open when ripe to reveal masses of juicy, deep-red pulp filled
with tiny black seeds. Pulp and seeds are consumed by several kinds of
birds, especially white-winged doves. Many fruits that fall to the
ground are promptly eaten by rodents and other animals.
Indians, too, eat the fruits. European explorers who followed Coronado’s
expedition into this region found peaceful Papagos and Opatas living
here, hunting animals and utilizing many native plants. Among the most
dependable of Papago food sources was the fruit of the giant cactus. So
important was this fruit harvest in their economy that they designated
this season as the start of the new year. Today, in some parts of the
desert, Pima and Papago Indians still harvest the fruits. The word
“saguaro” is believed to derive from a Spanish corruption of a Papago
word for the big cactus.
[Illustration: Spiny armor of the saguaro.]
[Illustration: Saguaro in full bloom.]
Saguaros provide not only food for man and beast, but homes for animals.
Walk through a giant cactus forest and you will be amazed at the number
of holes drilled in these plants. The holes are made by Gila woodpeckers
and related gilded flickers, which often relinquish them after one
nesting season. The next occupant may be any of a host of desert
dwellers, including screech and elf owls, purple martins, and
invertebrates. Some birds use the plant as a foundation for their homes.
White-winged doves, for instance, often build flimsy stick platforms on
the tips of saguaro arms; red-tailed hawks and horned owls construct
more substantial nests in the forks.
Although billions of saguaro seeds are produced yearly in the extensive
stands of the monument, only a very few find favorable locations for
germination and growth. Trees, rocks, dead limbs, pebbles—anything that
reduces evaporation in the immediate vicinity of the seed—improve the
chance of germination. These kinds of shelter not only provide the
necessary moisture conditions, but also hide the seed from armies of
ants, rodents, and other animals searching for food.
[Illustration: Saguaro blossoms.]
[Illustration: Saguaro fruit.]
Early growth is extremely slow. A 2-year-old saguaro may be only
one-quarter of an inch in diameter, and a 9-year-old plant may be 6
inches high. These years are the most hazardous. Insect larvae devour
the tiny cactuses. Woodrats and other rodents chew the succulent tissue
for its water, and ground squirrels uproot the young plants with their
digging. In later life, the saguaro must contend with uprooting wind and
human vandalism, as well as the earlier foes—drought, frost, erosion,
and animals.
[Illustration: Gila woodpecker at its nesting hole.]
In a century of maturity, a saguaro may produce 50 million seeds;
replacement of the parent plant would require only that one of these
germinate and grow. But in the cactus forest of the Rincon Mountain
Section, the rate of survival has been even lower, so that over the last
few decades the stand has been dwindling. What is wrong?
Many answers to this question have been advanced, but like all
interrelationships in nature, the saguaro’s role in the desert web of
life is very complex, and involves past events as well as present ones;
a partial answer to the problem may be all we can hope for. The
following reasons for the decline of the saguaros have been suggested by
researchers.
[Illustration: Saguaro, 1 foot high, in a rocky habitat.]
[Illustration: A typical 4-foot saguaro.]
There is some evidence to suggest that the Southwest has been getting
drier since at least the late 19th century, and while the saguaro is
adapted to extreme aridity, some of the “nurse” plants that shelter it
during infancy are not. If such shrubs as paloverdes and mesquites
dwindle, it is argued, so must the saguaro, which in its early years
depends on them for shade.
Other culprits in the saguaro problem are man himself and his livestock.
Around 1880, soon after the first railroad reached Tucson, a cattle boom
began in southern Arizona. The valleys were soon overstocked, and cattle
scoured the mountainsides in search of food. By 1893, when drought and
starvation decimated the herds, the land had been severely overgrazed.
Though the monument was established in 1933, grazing in the Rincon
Mountain Section’s main cactus forest continued until 1958. (Elsewhere
in the monument, it still goes on.) Compounding the problem, woodcutters
removed acres of mesquite and other trees. In the center of the present
Cactus Forest Loop Drive, lime kilns devoured quantities of woody fuel.
Further upsetting the desert’s natural balance, ranchers and Government
agents poisoned coyotes and shot hawks and other predators—in the belief
that this would benefit the owners of livestock.
This unrestrained assault on the environment had unfortunate effects on
saguaros as well as on the human economy. Overgrazing may have resulted
in an increase in kangaroo rats (which benefit from bare ground on which
to hunt seeds) and certain other rodents adapted to an open sort of
ground cover. Man’s killing of predators, their natural enemies, further
encouraged proliferation of these rodents, which some people say are
especially destructive of saguaro seeds and young plants. Whatever the
effect these rodents have on the saguaros, the removal of ground cover
intensified erosion and reduced the chances for the seeds to germinate
and grow. And certainly the cutting of desert trees removed shade that
would have benefited young saguaros. In the Tucson Mountain Section,
which is near the northeastern edge of the Sonoran Desert, freezing
temperatures are perhaps the most important environmental factor in
saguaro mortality.
[Illustration: Looking toward the Santa Catalina Mountains from
Cactus Forest Drive in September 1942.]
Although the causes of decline of the cactus forest lying northwest of
Tanque Verde Ridge are still something of a puzzle, several facts are
clear: the saguaro is not becoming extinct; in rocky habitats many young
saguaros are surviving, promising continued stands for the future; in
non-rocky habitats, some young saguaros are surviving, ensuring that at
least thin stands will endure in these areas. Furthermore, since grazing
was stopped here, ground cover has improved—a plus factor for the
saguaro’s welfare. On the negative side, it is possible that, in
addition to suffering from climatic, biotic, and human pressures, the
once-dense mature stands of the monument are in the down-phase of a
natural fluctuation. It is possible, too, that these stands owed their
exceptional richness to an unusually favorable past environment which
may not occur again. We can hope, however, that sometime in the
not-distant future the total environmental balance will shift once again
in favor of the giant cactus.
[Illustration: A photograph taken from the same spot in January
1970.]
_Other Common Cactuses_
Many other cactuses share the saguaro’s environment. The BARREL CACTUS
is sometimes mistaken for a young saguaro, but can easily be
distinguished by its curved red spines. Stocky and unbranching, this
cactus rarely attains a height of more than 5 or 6 feet. It bears
clusters of sharp spines, called “areoles,” with the stout central spine
flattened and curved like a fishhook. In bloom, in late summer or early
autumn, this succulent plant produces clusters of yellow or orange
flowers on its crown. The widely circulated story that water can be
obtained by tapping the barrel cactus has little basis in fact, although
it is possible that the thick, bitter juice squeezed from the plant’s
moist tissues might, under extreme conditions, prevent death from
thirst. Desert rats, mice, and rabbits, carefully avoiding the spines,
sometimes gnaw into the plant’s tissues to obtain moisture.
The group of cactuses called opuntias (oh-POON-cha) have jointed stems
and branches. They are common and widespread throughout the desert and
are well represented in the monument.
Those having cylindrical joints are known as chollas (CHO-yah), while
those with flat or padlike joints are called pricklypears.
Chollas range in size and form from low mats to small trees, but most of
those in the monument are shrublike. TEDDY BEAR CHOLLA, infamous for its
barbed, hard-to-remove-from-your-skin spines, forms thick stands on warm
south- or west-facing slopes. Its dense armor of straw-colored spines
and its black trunk identify it. Because its joints break off easily
when in contact with man or animal, this uncuddly customer is popularly
called “jumping cactus.” A similar species is CHAIN FRUIT CHOLLA,
notable for its long, branched chains of fruit, which sometimes extend
to the ground. Each year, the new flowers blossom from the persistent
fruit of the previous year. There is a common variety of this species
that is almost spineless. STAGHORN CHOLLA, an inhabitant primarily of
washes and other damp places, is named from its antler-shaped stems.
This cactus’ scientific name—_Opuntia versicolor_—refers to the fact
that its flowers, which appear in April and May, may be yellow, red,
green, or brown. (Each plant sticks with one color through its
lifetime.) Among the smaller chollas, thin-stemmed PENCIL CHOLLA grows
from 2 to 4 feet high on plains and sandy washes. DESERT CHRISTMAS
CACTUS, almost mat-like in form, blooms in late spring but develops
brilliant red fruits which last through the winter.
[Illustration: Barrel cactus blossoms.]
[Illustration: Barrel cactus spines.]
[Illustration: Chain fruit cholla at Tucson Mountain Section
headquarters.]
PRICKLYPEARS, like many of the chollas, produce large blossoms in late
spring. Those on the monument are principally the yellow-flowered
species. The reddish brown-to-mahogany colored edible fruits, called
tunas, attain the size of large strawberries. When mature in autumn,
they are consumed by many desert animals.
Some of the smaller cactuses are so tiny as to be unnoticeable except
when in bloom; examples are the HEDGEHOGS, the FISHHOOKS, and the
PINCUSHIONS. Blossoms of some of these ground-hugging species are large,
in some cases larger than the rest of the plant, and spectacular in form
and color. All add to the monument’s spring and early summer display of
floral beauty.
Non-Succulents
For the diversity of devices for adaptation to an inhospitable
environment, the many species making up the non-succulent desert
vegetation provide an absorbing field for study. As we have seen, there
are two ways to survive the harsh desert climate; one is to avoid the
periods of excessive heat and drought (“escapers”); the other is to
adopt various protective devices (“evaders” and “resisters”).
Short-lived plants follow the first method; perennials, the second.
_Perennials_
Chief among the requirements for year-round survival in the desert is a
plant’s ability to control transpiration and thus maintain a balance
between water loss and water supply. In this struggle, the hours of
darkness are a great aid because in the cool of the night the air is
unable to take up as much moisture as it does under the influence of the
sun’s evaporating heat. Therefore, less exhaling and evaporating of
water occurs from plants, and both the rate and the amount of water loss
are reduced. This reduction in transpiration at night allows the plants
to recover from the severe drying effects of the day. One biologist may
have been close to the truth when he stated, “If the celestial machinery
should break down so that just one night were omitted in the midst of a
dry season, it would spell the doom of half the nonsucculent plants in
the desert.”
One of the common trees in the desert part of the monument is the
MESQUITE (mess-KEET). In general appearance it resembles a small, spiny
apple or peach tree with finely divided leaves. Its roots sometimes
penetrate to a depth of 40 or more feet, thus securing moisture at the
deeper, cooler soil levels, from a supply that remains nearly constant
throughout the year. This enables the tree to expose a rather large
expanse of leaf surface without losing more water than it can replace. A
number of mechanical devices help the tree reduce its water loss during
the driest part of the day (10 a.m. to 4 p.m.). Among these are its
ability to fold its leaves and close the stomata (breathing pores),
thereby greatly reducing the surface area exposed to exhaling and
evaporating influences. In April and May, mesquite trees are covered
with pale-yellow, catkinlike flowers which attract swarms of insects.
These flowers develop to stringbeanlike pods rich in sugar and important
as food for deer and other animals. In earlier days, the mesquite was
also a valuable source of food and firewood for Indians and pioneers.
[Illustration: Pricklypear blossom.]
[Illustration: Claret cup hedgehog.]
[Illustration: Fishhook cactus.]
[Illustration: Cholla in bloom.]
[Illustration: Staghorn cholla.]
Another desert tree abundant in the monument is the YELLOW PALOVERDE. It
is somewhat similar in size and general shape to the mesquite. Lacking
the deeply penetrating root system of the mesquite, the paloverde
(Spanish word meaning “green stick”) has no dependable moisture source;
but it has made unusual adaptations that enable it to retain as much as
possible of the water collected by its roots. In early spring the tree
leafs out in dense foliage, which is followed closely by a blanket of
yellow blossoms. At this season the paloverdes provide one of the most
spectacular displays of the desert, particularly along washes, where
they grow especially well. Blue paloverde, growing in the arroyos,
blooms well every year. Yellow, or foothill, paloverde, a separate
species, blooms only if the soil moisture is high following winter
rains.
With the coming of the hot, drying weather of late spring, the trees
need to reduce their moisture losses. They gradually drop their leaves
until, by early summer, each tree has become practically bare. The trees
do not enter a period of dormancy, but are able to remain active because
their green bark contains chlorophyll. Thus, the bark takes over some of
the food-manufacturing function normally performed by leaves, but
without the high rate of water loss.
Carrying the drought-evasion habits of the paloverde a step further, the
OCOTILLO (oh-koh-TEE-yoh) comes into full leaf following each rainy
spell during the warmer months. During the intervening dry periods it
sheds its foliage. The ocotillo, a common and conspicuous desert
dweller, is a shrub of striking appearance, with thorny, whiplike,
unbranching stems 8 to 12 feet long growing upward in a funnel-shaped
cluster. In spring, showy scarlet flower clusters appear at the tips of
the stems, making each plant a glowing splash of color.
[Illustration: Mesquite in bloom.]
A number of desert shrubs fail to display as much ingenuity as the
paloverde. Some of these evade the dry season simply by going into a
state of dormancy. The WOLFBERRY bursts into full leaf soon after the
first winter rains and blossoms as early as January. Its small,
tomato-red, juicy fruits are sought by birds, which also find protective
cover for their nests and for overnight perches in the stiff, thorny
shrubs. In the past, the berrylike fruits were important to the Indians,
who ate them raw or made them into a sauce.
[Illustration: Yellow paloverde, Tucson Mountain Section.]
Commonest of the conspicuous desert non-succulent shrubs is the
wispy-looking but tough CREOSOTEBUSH, found principally on poor soils
and on the desert flats between mountain ranges. It is also sprinkled
throughout the paloverde-saguaro community in the monument. A new crop
of wax-coated, musty-smelling leaves, giving the plant the local (but
mistaken) name “grease-wood,” appears as early as January. The leaves
are followed by a profuse blooming of small yellow flowers and cottony
seed balls. During abnormally moist summers or in damp locations, the
leaves and flowers persist the year round; but usually the coming of dry
weather brings an end to the blossoming period. If the dry spell is
exceptionally long, the leaves turn brown, and the plants remain dormant
until awakened by the next winter’s rainfall. Pima Indians formerly
gathered a resinous material, known as lac, which accumulates on the
bark of its branches, and used it to mend pottery and fasten arrow
points. They also steeped the leaves to obtain an antiseptic medicine.
Ground squirrels commonly feed on the seeds.
[Illustration: Ironwood blossoms.]
[Illustration: Parry’s penstemon.]
A large shrub of open, sprawling growth usually found along desert
washes in company with mesquite is CATCLAW. Its name refers to the small
curved thorns that hide on its branches. In April and May, the small
trees are covered with fragrant, pale-yellow, catkinlike flower clusters
that attract swarms of insects. The seed pods were ground into meal by
the Indians and eaten as mush and cakes.
In lower elevations of the Tucson Mountain Section, the gray-blue
foliage of IRONWOOD is a common sight, but the species does not range
farther eastward. Its wisterialike lavender-and-white flowers blossom in
May and June. The nutritious seeds are harvested by rodents and formerly
were parched and eaten by Indians. The wood is so dense that it sinks in
water; Indians used it for making arrowheads and tool handles.
Ferns—commonly, plants of dank woods and other moist habitats—seem
entirely out of place in the desert; nevertheless, some members of the
fern family have overcome drought conditions. The GOLDFERN is common on
rocky ledges, where it persists by means of special drought-resistant
cells.
Among the smaller perennials are many that add to spring flower displays
when conditions of moisture and temperature are favorable. Perennials do
not need to mature their seeds before the coming of summer as do the
ephemerals; a majority start blossoming somewhat later in the spring,
and gaily flaunt their flowers long after the annuals have faded and
died. When the heat and drought of early summer begin to bear down, they
gradually die back, surviving the “long dry” by their persistent roots
and larger stems. One of the most noticeable and beautiful of this group
of small perennials fairly common in the monument is PARRY’S PENSTEMON.
It occurs in scattered clumps on well-drained slopes along the base of
Tanque Verde Ridge. The showy rose-magenta flowers and the glossy-green
leaves arise from erect stems that may grow 4 feet tall in favorable
seasons.
Among the first of the shrubby perennials to cover the rocky hillsides
with a blanket of winter and springtime bloom is the BRITTLEBUSH. Masses
of yellow sunflowerlike blossoms are borne on long stems that exude a
gum which was chewed by the Indians and was also burned as incense in
early mission churches.
A conspicuous perennial that survives the dry season as an underground
bulb is BLUEDICKS. Although it doesn’t occur in massed bloom, it does
add spots of color to the desert scene. Usually appearing from February
to May, bluedicks has violet flower clusters on long, slender, erect
stems. The bulbs were dug and eaten by Pima and Papago Indians.
Although neither conspicuous nor attractive, the common TRIANGLE BURSAGE
is an important part of the paloverde-saguaro community in the Tucson
Mountains. A low, rounded, white-barked shrub, bursage has small,
colorless flowers without petals. (Being wind-pollinated, the flowers do
not need to attract insects.)
One of the handsome shrubs abundant in the high desert along the base of
Tanque Verde Ridge is the JOJOBA (ho-HOH-bah), or deernut. Its thick,
leathery, evergreen leaves are especially noticeable in winter and
furnish excellent browse for deer. The flowers are small and yellowish,
but the nutlike fruits are large and edible, although bitter. They were
eaten raw or parched by the Indians, and were pulverized by early-day
settlers for use as a coffee substitute.
Among the attractive flowering shrubs are the INDIGOBUSHES, of which
there are several species adapted to the desert environment. The local,
low-growing indigobushes are especially ornamental when covered with
masses of deep-blue flowers in spring.
Another small shrub, noticeable from February to May because of its
large, tassel-like pink-to-red blossoms and its fernlike leaves is
FAIRY-DUSTER. Deer browse on its delicate foliage.
The PAPER FLOWER, growing in dome-shaped clumps covered with yellow
flowers, sometimes blooms throughout the entire year. The petals bleach
and dry and may remain on the plant weeks after the blossoms have faded.
Quick to attract attention because of their apparent lack of foliage,
the JOINTFIRS, of which there are several desert species, grow in clumps
of harsh, stringy, yellow-green, erect stems. The skin or outer bark of
the stems performs the usual functions of leaves, which on these plants
have been reduced to scales. Small, fragrant, yellow blossom clusters,
appearing at the stem joints in spring, are visited by insects attracted
to their nectar.
_Ephemerals_
Every spring, after a winter of normal rainfall, parts of the
southwestern deserts are carpeted with a lush blanket of fast-growing
annual herbs and wildflowers—the early spring ephemerals. The monument
does not get massive displays, however, since it is lacking in the
species that make the best show. But it does have many annuals that are
beautiful individually or in small groups. Many of these “quickies” do
not have the characteristics of desert plants; some of them, in fact,
are part of the common vegetation of other climes where moisture is
plentiful and summer temperatures are much less severe.
What are these “foreign” plants doing in the desert, and how do they
survive? With its often frostfree winter climate and its normal
December-to-March rains, the desert presents in early spring ideal
growing weather for annuals that are able to compress a generation into
several months. Several hundred species of plants have taken advantage
of this situation.
There is WILD CARROT, which is a summer plant in South Carolina and a
winter annual in California (where it is called “rattlesnake weed”). In
the desert, its seeds lie dormant in the soil through the long, hot
summer and the drying weather of autumn. Then, under the influence of
winter rains and the soil-warming effects of early spring sunshine, they
burst into rapid growth. One of a host of species, this early spring
ephemeral is enabled by these favorable conditions to flower and mature
its seed before the pall of summer heat and drought descends upon the
desert. With their task complete, the parents wither and die. Their
ripened seeds are scattered over the desert until winter rains enable
them to cover the desert with another multicolored but short-lived
carpet of foliage and bloom.
The one-season ephemerals do not limit themselves to the winter growing
period. From July to September, local thundershowers deluge parts of the
desert while other areas, not so fortunate, remain dry. Where rain has
fallen, another and entirely different group of plants, called the
summer ephemerals, find ideal conditions for growth and take their turn
at weaving a desert carpet. Their seeds have lain dormant over winter.
These summer “quickies” are plants that, farther south in Baja
California and Sonora, Mexico, flourish during the winter rainy season.
Saguaro National Monument is doubly fortunate in that it lies within a
section of desert having not only its own year-round vegetation, but
also summer wildflowers “borrowed,” for winter use, from its eastern and
western neighbors, and winter wildflowers for summer decorations from
its southern neighbors.
[Illustration: Phacelia, an ephemeral.]
The short-lived leafy plants of summer and winter are able to compress
their entire active life into 6 to 12 weeks when conditions are most
suitable. Thus, they can escape all the rigorous periods of the desert
climate by living for 8 or 9 months in the dormant seed stage. Some of
the spectacular and colorful flowers of the monument are among these
ephemerals that survive desert conditions by escaping them. It must be
remembered, however, that when drought conditions or abnormally cold
spring weather upset the norm—a not unusual occurrence—response of
ephemeral plants is greatly restricted. If suitable conditions do not
develop during the season for growth of a particular kind of ephemeral,
its seeds will simply wait a year or more until conditions are
favorable.
[Illustration: White tackstem.]
How do the seeds of ephemerals “know” when it is time to germinate?
Experiments have revealed that the seeds of annuals will germinate only
when enough water percolates through the soil to dissolve away a “growth
inhibitor” in their coats. A single light rain will not do the job. In
this way premature sprouting into a too-dry environment is prevented.
The winter annuals, furthermore, will only germinate when soils are
cool, and the summer annuals when soils are warm. These finely tuned
adaptations thus allow plantlife to take full advantage of favorable
seasons in the desert.
Early spring ephemerals climax their show in March. From late February
to mid-April they are completing their growth and putting forth the
precious seeds that will assure survival for the next generation. At the
head of this parade of flowers in the monument is a purple-blossomed
immigrant from the Mediterranean, the now thoroughly naturalized
FILAREE. In addition to the small purple flowers, which may appear as
early as January, the conspicuous “tailed” fruits almost always attract
attention. When dry, they are tightly twisted, corkscrewlike; when damp
they uncoil, forcing the needle-tipped seeds into the soil.
[Illustration: Desert-marigold.]
INDIAN WHEAT is one of the first plants to lay a green carpet over the
sandy desert floor in spring. The tan, individual flower heads are
conspicuous, but their numerous, close-growing spikes form a thick,
luxuriant, pilelike ground cover. The countless tiny seeds are eagerly
sought each spring by coveys of Gambel’s quail, and are also harvested
by Pima and Papago Indians.
DESERT CHICORY is somewhat like the common yellow dandelion but is
longer stemmed and less coarse. Its white or butter-yellow blossoms make
it one of the noticeable spring annuals in the desert. It rarely grows
in pure stands but appears in conspicuous clumps among other short-lived
plants.
Somewhat similar in appearance to desert chicory is WHITE TACKSTEM, one
of the handsomest of the spring quickies. It is usually found on dry,
rocky hillsides and has white or rose-colored flowers. Its name is
derived from the presence of small glands which protrude in the manner
of tiny tacks partially driven into the stems.
Following abnormally wet winters, FIDDLENECK covers patches of sandy or
gravelly soil with a dense growth of bristly erect plants. These bear
tight clusters of small yellow-orange blossoms arranged along a curling
flower stem resembling the scroll end of a violin, hence the name. This
plant, favored by the same growing conditions as creosotebush,
frequently forms a dense though short-lived growth around the bases of
those shrubs.
Associated with fiddleneck and creosotebush, SCORPIONWEED adds its
violet-purple blooms to the spring flower display following winters of
above-normal precipitation. The name is derived from the curling habit
of the blossom heads, which may remind the observer of the flexed tail
of a scorpion. Touching the plant may cause skin irritation in
susceptible individuals. Unfortunately, scorpionweed is also widely
known as wild-heliotrope, thus contributing to the confusion engendered
by duplication of popular names. The plant properly called
WILD-HELIOTROPE is similar in general appearance, but the flowers are
white to pale purple and their odor is more pleasing than that of the
scorpionweed. Wild-heliotrope, or “quailplant,” is another of the early
spring ephemerals, but under favorable conditions, where soils are
moist, it may continue to live and bloom throughout the year.
[Illustration: Bladder-pod.]
Growing in sandy locations and quite noticeable because of its large,
yellow, showy, long-stemmed flower heads, the DESERT-MARIGOLD helps to
open the spring blossoming season. Where moisture conditions are
favorable, these plants may continue to bloom throughout the summer and
well into autumn. Sometimes, during the hottest, driest time of the
year, desert-marigolds are among the very few blossoms brightening the
desert floor. Their bleached, papery petals persist for days after the
flowers have faded, giving the plant the name paper-daisy.
One of the few species that makes a carpet of color in the monument is
the tiny BLADDER-POD. This low-growing annual of the mustard family
begins to cover open stretches of desert with a yellow blanket in late
February or early March following wet winters. Bladder-pod is usually
found in pure stands surrounding islands of cholla, creosotebush, and
paloverde. It also mingles with other spring ephemerals, where it is
promptly submerged by the ranker, taller-growing, more conspicuous
annuals.
Illustrating one of the interesting phases in evolutionary variations
among plants, the LUPINES are represented by several species which are
able to survive and prosper in the desert. Some of the lupines are
annuals of the quickie type; others are perennials with a life cycle of
several years. Some of these longer-lived species join the ephemerals in
the spring flower show, while others are more leisurely in approaching
their blossoming time.
[Illustration: The Desert Scrub Community occupies the lower parts
of the monument, from about 2,200 to 4,000 feet.]
[Illustration: The Grassland Transition begins at about 3,500 feet
(overlapping in altitude with the Desert Scrub) and extends to 4,500
feet.]
major plant communities
of saguaro
[Illustration: SAGUARO NATIONAL MONUMENT]
Tucson Mountain Section
Biotic Communities
Desert Scrub
Grassland
Transition
In any region where a great range of altitude exists, the vegetation
grows in a continuum of overlapping but recognizable zones. Climate
being the major controlling factor of this zonal distribution, the
plants of each band grow higher on south-facing slopes than on cooler,
moister north slopes. In Saguaro the major plant communities roughly
correspond to altitudinal bands—with the desert at the lower, drier
levels, and the transition through grasses and shrubland to forest
community occurring with increasing altitude (and increasing rainfall).
Timberline—the boundary between high mountain forests and the alpine
meadows and barrens—does not exist in Saguaro, where trees clothe the
highest peaks.
The fauna of each community is made up of animals adapted to the
climatic conditions and the available food, cover, and water. In
Saguaro, some animals, such as the desert kangaroo rat and the cactus
wren, are restricted by their life requirements to a narrow belt;
others, such as the gray fox and great horned owl, are more adaptable
and live in all the major plant communities.
[Illustration: SAGUARO NATIONAL MONUMENT]
Rincon Mountain Section
Biotic Communities
Desert Scrub
Grassland Transition
Oak Woodland
Oak-Pine Woodland
Ponderosa Pine Forest
Douglas-fir Forest
[Illustration: The Open Oak Woodland has scattered trees associated
with many plants of the Grassland Transition.]
[Illustration: The Oak-Pine Woodland, from 4,500 to 7,000 feet,
occupying a slightly cooler, wetter environment than those below, is
broken by open glades and grassy hillsides.]
[Illustration: The Ponderosa Pine Forest, unlike the Oak-Pine “pygmy
woodland,” has tall trees growing in clear, open stands. It covers
much of the Rincon Mountains above 6,000 feet.]
[Illustration: The Douglas-fir Forest, limited to the higher
northern and northeastern slopes of Mica Mountain and the north side
of Rincon Peak, often contains aspens and white firs.]
[Illustration: Spanish dagger, with Rincon Peak in the background.]
plants of the hills
and mountains
Most visitors to the monument see only a small part of it—the lowland
cactus forests. But above the desert in the high back country of the
Rincon Mountains is another world. These highlands are accessible only
on foot or horseback; and they should remain so, for they are now in the
last major roadless range in southern Arizona, and as such their
wilderness value appreciates yearly. Interesting scenic trails reach the
high places of the Tucson Mountains, too, but to see the greatest
changes in plantlife you must climb the higher Rincons.
Oak-Pine Woodland
The thinning and final disappearance of saguaros along the trailside,
although mesquite and ocotillos seem almost as numerous as on the floor
of the desert, indicate that you are entering a slightly cooler, wetter
environment. An occasional MEXICAN BLUE OAK or ARIZONA ROSEWOOD appears
among the mesquites along the washes. The grasses that increasingly
cover the ground as you climb include HAIRY, SIDEOATS, and SPRUCETOP
GRAMA; CURLY MESQUITEGRASS; TANGLEHEAD; TEXAS BLUESTEM; and WOLFTAIL.
Mingling with them are TURPENTINE-BUSH and shrubby SNAKEWEED.
A spectacular inhabitant of the grassland transition and open oak
woodlands you are now entering is the AMOLE, or SHINDAGGER, whose
rapidly growing blossom stalks attract attention from May to as late as
August. The plants themselves, which grow crowded together in patches,
consist of rosettes of succulent leaves superficially resembling bunches
of flattened, green bananas. The stiff, needle-sharp leaf tips can
inflict painful jabs on man and beast. During its lifetime, the plant
stores food in its short, thick stem. Finally, after several years, it
sends up an unbranched flower stalk that grows to 5 feet. The
light-yellow flowers mature to brown, capsule-like fruits, after which
the plant dies. The short stems or crowns, containing saponin, were used
by Indians as soap. They also roasted the young bud stalks of some
species by covering them with heated stones in pits.
Two noticeable plants of the lily family which sometimes dominate
gravelly slopes of the grassland-oak woodland belt are the SOTOL and
BEARGRASS, or sacahuista. The former grows from a compact crown as a
dense, rather symmetrical cluster of long, thin ribbonlike leaves,
usually grayed at the tips and armed along the margins with curved
thorns. In early summer many small, cream-colored blossoms develop along
the upper extremity of single fast-growing flower stalks 8 to 10 feet
high. The bud stalks formerly were harvested and roasted by Indians. In
Mexico a potent alcoholic drink, sotol, is distilled from the fermented
juice of the pounded crowns. Sacahuista resembles huge, sprawling
clusters of coarse grass. Flower stalks are short, producing
conspicuous, open, loose sprays of small, tan-to-brownish flowers in May
and June. Indians used the tender bud stalks for food and obtained fiber
from the long, slender leaves, weaving them into baskets and mats.
[Illustration: Mexican blue oak foliage.]
Uncommon in the monument, but worthy of mention, are ARIZONA SYCAMORE
and ARIZONA CYPRESS. The latter is restricted to the east flank of the
Rincon Mountains, steep slopes, and deep canyons, where it grows with
the SILVERLEAF, PALMER, EMORY, and NETLEAF OAKS; mesic shrubs; poison
oak; and CALIFORNIA BUCKTHORN. Arizona sycamore grows along lower-canyon
watercourses such as Chiminea and Rincon Creeks, which drain the rugged
south flank of Mica Mountain and the west flank of Rincon Peak,
respectively.
As you continue to climb, the open, grassy, shrub-dotted slopes change
in places to sprawling thickets, called chaparral. These are made up of
manzanita and skunkbush, SILKTASSEL, evergreen oaks, and underbrush of
smaller shrubs. Among the common oaks are ARIZONA WHITE OAK and, on
drier sites of the Tanque Verde range, SHRUB LIVE OAK. The oaks furnish
protective cover, browse, and acorns for deer and other mammals and
birds, and are of great value in retarding soil erosion on steep
gravelly slopes.
[Illustration: Turpentine-bush, a member of the sunflower family.]
POINTLEAF MANZANITA is especially abundant on the lower eastern flanks
of the Rincon Mountains in the Happy Valley area. Early in spring the
waxy, urn-shaped blossoms, the leathery, glossy, evergreen leaves, and
the typical grotesquely crooked, red-barked limbs, make manzanita one of
the most attractive shrubs of the chaparral.
Although SKUNKBUSH is a close relative of poison ivy and sumac, its
aromatic foliage is harmless. Growing in compact thickets, skunkbush
provides food and cover for birds and other small animals. Inconspicuous
yellow flowers appear from March to June, and are followed by berrylike
fruits which are dull red when mature.
As you follow the trail higher, occasional MEXICAN PINYON PINES and
ALLIGATOR JUNIPERS appear. Gradually these evergreens become more
abundant, mingling with the oaks to form a pigmy oak-pine-juniper
forest. Clumps of MOUNTAIN-MAHOGANY are noticeable, their feathery seed
“tails” gleaming in the sunshine.
Pinyons are among the commonest and most widespread trees of the middle
elevations throughout the Southwest. The Mexican pinyon, which is the
species growing abundantly in the Tanque Verde-Rincon upland, may be
recognized by the fact that its foliage is in clusters of three needles
to the bundle. Its cones require nearly 2 years to mature and contain
hard-shelled seeds or nuts which are a source of food for many birds and
mammals. These pines are usually shrubby, rarely more than 15 to 25 feet
high, with horizontal, twisted, low-growing limbs. Intermingled with the
pinyons are alligator junipers, often mistakenly called cedars. Those in
the monument are conspicuous because their platy bark forms an
attractive pattern resembling the squarish-scaled skin of alligators.
The berrylike cones are soft and mealy, and are eaten by many kinds of
wild animals.
Although the oak-pine woodland supports a heavy stand of shrubby trees
over much of the terrain, there are numerous open glades and grassy
hillsides. In addition to some of the aforementioned grasses, BLUEGRASS,
BULLGRASS, and PLAINS LIVEGRASS provide ground cover in this belt.
Following summer showers, many flowering herbs brighten the open slopes.
Yellow to orange petals of PUCCOON, and the white to lavender-and-rose
blossoms of MOCK-PENNYROYAL and HOUSTONIA are among those seen along the
trailside.
Ponderosa Pine Forest
Just as grassland merges with oak woodland and chaparral, and these with
oak-pine woodland, so you will notice, as you climb steadily higher,
that these woodlands gradually mingle with the open pine forests that
cover much of the Rincon Mountains above 6,000 feet. PONDEROSA PINE is
the “big tree” of the Rincons, usually growing in clear, open stands.
Through its high canopy of spreading branches, sunlight mottles the
shaded forest floor. Its presence indicates still cooler and wetter
conditions than those below. Here you will need blankets at night,
though summer days are warm.
Except for grasses such as PINE DROPSEED, SCREWLEAF MUHLY, and MOUNTAIN
MUHLY, ground cover is scarce. In tree-glades or on old burns, however,
intermediate-type shrubs (such as BUCKBUSH) and various herbs have
established themselves. Some herbs develop into patches of colorful
flowers in summer and autumn. Common flowering plants found among the
pines are COLOGANIA; PEAVINE, with its large and showy, white,
sweetpea-like blossoms throughout the summer; lupines; DOGBANE; and the
familiar white WESTERN YARROW. Here, too, may be found GROUNDSEL, ASTER,
FLEABANE, and others, often brightened by the presence of butterflies
and other insects seeking nectar and pollen. Most of these forest
flowers bloom in late summer or autumn, when plants in the desert, far
below, are drab and dormant.
Throughout the pine forests, numerous small canyons and rocky outcrops
favor the development of thickets of oak and locust, frequently growing
together. GAMBEL’S OAK, a leaf-shedding white oak, ranges in size from a
small shrub to a handsome tree. It has broad, deeply lobed leaves which
provide browse for deer. Its acorns are consumed by deer, rodents, and
birds, including wild turkeys. The NEW MEXICAN LOCUST also is browsed by
deer. Rarely reaching tree size, this species is an attractive
vegetative cover because of its odd-pinnate leaves and large clusters of
purplish-pink flowers that appear in May and June. Locusts sprout freely
from roots and form expanding thickets which encroach upon oak clumps.
They provide a valuable network of soil-holding roots, important in
retarding erosion. The best stands occur along the east slopes of the
Rincons.
Relatively few in number, compared with the stands of the dominant
ponderosa pine, the smaller CHIHUAHUA PINE grows on lower dry slopes and
benches. Its needles are shorter than those of the ponderosa pine, and
its cones are conspicuously persistent, remaining on the tree for
several years. This Mexican species invades the United States in the
mountain ranges of southern Arizona and southwestern New Mexico. In the
monument it is found mostly in the transition areas between oak-pine
woodland and ponderosa pine forest.
The Rincon Mountains are not high enough to provide a fir-forest habitat
except in a few favorable locations. On the highest parts of the
Rincons, ponderosa pines dominate in the warmer, exposed locations, but
whitebarked QUAKING ASPENS grow in pure stands on cooler slopes and with
DOUGLAS-FIRS on the north side of Rincon Peak. West of Spud Rock are
abundant small groves of MEXICAN WHITE PINE.
A cone-bearing tree growing with Douglas-fir—exclusively on higher
northern and northeastern slopes of Mica Mountain—is the WHITE FIR.
Flattened, gray-green needles curving upward from the branches, and
large, green cones growing upright on limbs near the tops of the trees
identify this beautiful evergreen. On open stands, limbs of even the
large trees grow from the trunk almost down to the ground. The bark is
gray or ash-colored.
BRACKEN forms a green ground cover in heavy stands of pine and fir. This
fern grows 3 feet tall over much of the forested Rincon highland. Among
the shrubs found on the mountaintop is the SNOWBERRY, whose leaves are
browsed by deer and whose berries are eaten by birds and chipmunks.
A spring, a small mountain stream, and a meadow near Manning Camp
complete the picture of the higher elevations in the monument. In this
bit of meadowland are found BOXELDER, NEW MEXICAN ALDER, CINQUEFOIL,
CHOKECHERRY, GOLDENROD, ORANGE SNEEZEWEED, MARIGOLD, WILLOW, and a
number of other shrubs, grasses, and herbs characteristic of the high
mountain meadows of the Southwest.
[Illustration: Jerusalem cricket (of a different family from the
true crickets) has legs adapted for tunneling in sand.]
animals
and how they survive
Just as plants depend for their existence on soil, water, and sunlight,
so animals, including man, depend on plants. For green plants are the
basic food producers in nature, manufacturing carbohydrates, proteins,
and other essential compounds from minerals, air, and water, with the
help of chlorophyll and the sun’s energy. Animals get their food either
by eating green plants or by eating animals that have eaten plants.
Microscopic decomposers complete this food chain, breaking down dead
plants and animals into substances that once again can be used by
plants. Since each link in the chain depends on the other links, it’s
not hard to see that a change in one will cause a change in the others.
And because animals depend on plants for cover as well as for food,
their fortunes are doubly tied to the welfare of plants.
Animals and plants share some of the same basic problems—particularly,
how to stay within tolerable temperature limits, and how to maintain an
adequate supply of water. Plants solve these problems mostly by
structural adaptations, animals mostly by behavioral. In the desert, for
instance, cold-blooded animals such as snakes and lizards (which have no
internal control over body temperature) crawl underground or into shade
during the midday heat of summer, and come out to hunt food during the
cooler hours. Birds and mammals cool themselves through evaporation of
water from their bodies. This makes water conservation doubly critical
for them; they too handle it by staying in the shade or going
underground during hot times. Desert animals get much of their water
from the plants and animals they eat, but some species, such as mule
deer and Gambel’s quail, require large amounts of drinking water as
well.
Cold weather poses another problem. Most reptiles and some mammals solve
this one by hibernating underground or in rock dens, where temperatures
remain moderate throughout the year. Many birds and some mammals migrate
to areas where temperatures are warmer and food is more abundant, which
may mean going farther south or simply moving down the mountainsides.
And insects can survive in a dormant form, as eggs or pupae, though many
species remain active during the temperate Sonoran winters.
If you want to see animals, then, go where the vegetation is thickest
and most varied, and go when temperatures are moderate. During warm
seasons in the desert, this means that walking the washes early or late
in the day will give you the best chances for seeing wildlife. Coveys of
Gambel’s quail explode into the air, peccaries snort through the
underbrush, butterflies festoon flowering shrubs, and coyotes stealthily
hunt.
Invertebrates
Insects are generally not bothered by excessive heat, and many species
are active during the hottest hours. This is especially true when the
plant blossoming season is at its height. Flowers of the mesquite,
paloverde, catclaw, saguaro, and other desert plants are “alive” all
through the day, as many species of insects seek nectar and pollen or
prey on other insects attracted to the blossoms. Insects are fed upon by
various species of birds; flycatchers flock to parts of the desert where
nectar-yielding flowers are numerous. Because of the absence of extreme
cold, the desert climate enables insects to be active throughout much of
the year and to support a considerable bird population.
[Illustration: Despite its fearsome appearance and reputation, you
have nothing to fear from the tarantula.]
Insects play a far more important role in the plant and animal life of
the desert than is usually realized. Many desert flowers must be insect
pollinated to produce viable seeds. Birds of many kinds depend upon
insects for food, and even the seed-eating birds, during the nesting
season, rely upon insects to provide the enormous quantities of food and
moisture required by their fast-growing nestlings. Many other desert
creatures, including certain snakes and lizards and some spiders, depend
upon insects for food. The body juices of the insects provide the
all-important moisture—which these creatures can get from no other
source. Bats, too, are insect eaters, spending the hours of darkness in
seemingly aimless and erratic flight while foraging for moths and other
night-flying insects that visit the light-colored blossoms of
night-blooming plants.
Some species of insects may become so numerous that they threaten the
very life of the plants on which they live. Pine bark beetles annually
damage or kill numbers of pinyons and ponderosas in the Rincon
Mountains, but have been kept sufficiently under control by their
natural enemies so that their ravages have not reached epidemic
proportions.
Among the common spectacular insects is the TARANTULA HAWK, a large
blue-black, red-winged wasp that preys on large spiders. Temporarily
paralyzing the spider with its sting, the wasp lays a single egg on its
victim, thereby assuring an abundance of living food for its young. The
PRAYING MANTIS is another large insect, usually green and inconspicuous
among the foliage of desert plants, which it frequents in search of
small insects. Ants of many species are active almost everywhere in the
desert, harvesting seeds of various plants. Some species construct mazes
of underground nest tunnels and deposit the excavated materials on the
surface, forming conical, sometimes, craterlike, anthills.
[Illustration: The small desert hairy scorpion is the only scorpion
in the monument that is dangerous to humans.]
Along with the insects, other arthropods (jointed-leg creatures with
exoskeletons) find their home in the desert. The arachnids (eight-legged
arthropods) include spiders and scorpions. Of the former, the NORTH
AMERICAN TARANTULAS are famous for their large size and formidable
appearance, which have given them the wholly undeserved reputation of
being dangerous to humans. The really dangerous creatures are the
SCORPIONS, whose long, flexible tails bear a poisonous stinger at the
tip. Several species are found in the monument; but only the small,
straw-colored scorpion has venom known to have been fatal to humans. The
other scorpions found in the area can inflict painful stings, but with
only localized and rarely serious effects.
[Illustration: The Colorado River toad is exceeded in size among
U.S. toads only by the giant toad of south Texas (and Mexico).]
Amphibians
As might be expected, amphibians are scarce in the monument because of
lack of permanent water. The few springs and seeps, however, furnish
excellent breeding places for several species of amphibians. Best known
among these are the RED-SPOTTED TOAD, LEOPARD FROG, and CANYON TREEFROG,
the latter common near Manning Camp. A spectacular desert amphibian and
the second largest toad in the United States, is the huge COLORADO RIVER
TOAD, sometimes found near residences in the evening when outdoor lights
attract swarms of insects.
Reptiles
Except for small lizards, reptiles are not much in evidence in the
monument. Nevertheless, they are present and are important in the
various plant-and-animal communities in which they live. Almost all
lizards are insectivorous, and along with birds and other insect-eaters
help to keep the number of insects within bounds. A notable exception is
the GILA (HEE-lah) MONSTER, (See appendix for scientific names of
reptiles) largest of the lizards found in the United States. (It is one
of the world’s two poisonous lizards, and the only one found in this
country.) The gila monster is especially fond of bird eggs, and also
eats nestlings and small rodents, obtaining necessary moisture from
their body juices. These food habits are quite similar to those of the
several species of snakes found in the monument, the majority of which
are perfectly harmless to humans.
[Illustration: The short-horned lizard, more cold-tolerant than the
desert horned lizard, ranges from the foothills into the mountain
forests of Saguaro.]
Just as the lizards help to control the insect population, the snakes
are important in preventing the buildup of large numbers of rodents that
would result in widespread damage to vegetation. Visitors to the
monument rarely have the opportunity to observe snakes, since they are
in hibernation during winter and remain in the shade or in underground
burrows during the hot part of each summer day. Perhaps those most
frequently seen are the GOPHER SNAKE and the COACHWHIP. Many desert
snakes hunt only at night; others that are normally active during days
of moderate temperatures become night hunters during hot weather.
Although they are not abundant, there are several kinds of rattlesnakes
in the monument, the commonest desert species being the WESTERN
DIAMONDBACK and MOHAVE RATTLESNAKES. Except for the small, very rare,
and secretive ARIZONA CORAL SNAKE, rattlesnakes are the only poisonous
snakes in the monument. Snakes, like other living things in the national
monument, are protected by law.
Don’t be surprised while following a desert footpath to come upon a
plodding tortoise. This bona fide desert dweller, the DESERT TORTOISE,
is a vegetarian, feeding on cactus, grass, and other low-growing plants.
Birds
Because of its great variety of habitats, ranging from luxurious desert
vegetation to deep mountain forests, Saguaro National Monument provides
food and shelter for many species of birds. Some of these reside all
year within a single zone, while others move upward in summer, returning
to the desert when the mountaintops are covered with snow. Other species
pass through the monument in spring and autumn in their annual
migrations between Latin America and summer nesting grounds in northern
United States or Canada. The following species are those you are most
likely to see.
[Illustration: The Mojave rattlesnake prefers desert, grassland, and
open brushland to densely vegetated areas.]
A common year-round desert resident is the CURVE-BILLED THRASHER,
noticeable, noisy, and about the size of a robin. These energetic
inhabitants of the cactus forests nest in mesquite clumps and cholla
thickets. Their diet—they feed on insects and succulent fruits—makes
them comparatively independent of water. The thrashers are delightful
songsters. The CACTUS WREN, looking somewhat like a small thrasher, is
even noisier. It protects its nest by building in a cactus. This wren
lives largely on a diet of insects, but about 17 percent of its food is
seeds and fruits. One of the most attractive of the ground birds is the
GAMBEL’S QUAIL. Many coveys are found throughout the desert within close
range of water. In winter, Gambel’s quail feed mainly on seeds, berries,
and plant shoots; in summer they augment this diet with ants,
grasshoppers, and other insects. The ROADRUNNER, ungainly clown of the
desert, is frequently seen by visitors as it scuttles through the
underbrush along the margins of sandy washes. Not particular as to food,
it is sometimes seen with the tail of a lizard protruding from its beak,
and it is known to eat insects and spiders, snakes, young rodents, small
birds, seeds, and fruits. Quite capable of flight, the roadrunner
prefers to trust to its legs and the security of thickets, but will take
to its wings if pursued in the open.
[Illustration: You may mistake the curve-billed thrasher’s call,
“whit-wheet,” for a human whistle of attention.]
Two members of the woodpecker family closely associated with the saguaro
cactus are the GILA WOODPECKER and GILDED FLICKER. Called carpenter
birds because they drill nest holes or pockets in the saguaro stems,
both species are of particular interest because of their limited range
and specialized habitat. Two other desert birds, sufficiently similar to
be confused, are the red, black-faced CARDINAL and the gray-and-red
PYRRHULOXIA, both of which have crests. Look for these species in the
shrubs along washes. Several kinds of doves are found in the desert,
including the common MOURNING DOVE and the WHITE-WINGED DOVE. Mourning
doves are all-year residents, while the large white-wings drift in from
Mexico in May, remaining long enough to raise families and join other
animals in harvesting fruits of the saguaro.
[Illustration: The gilded flicker drills its nest hole in the
saguaro.]
Seen and heard in the desert all year, the canary-voiced HOUSE FINCH
raises its family among cholla and mesquite thickets. The tinkling song
of the ROCK WREN is a familiar sound in the desert in winter. These gray
ground dwellers go farther north or to higher elevations to nest.
The PHAINOPEPLA is one of the most noticeable of the desert birds
because of its silky crest, glossy black plumage, and habit of perching
on the topmost branch of a tree while indulging in flutelike song. A
permanent resident of the monument, subsisting on mistletoe berries and
other vegetable matter in winter, it has a diet of insects, principally
ants, during the rest of the year. Flycatchers are especially abundant
and conspicuous during spring and early summer when the blossoms of
trees, shrubs, and the larger cactuses attract swarms of insects. Among
these birds are SAY’S PHOEBE and ASH-THROATED FLYCATCHER. The LESSER
NIGHTHAWK lives on a diet of insects, which it catches while on the
wing. It is especially noticeable from May to September as it skims the
tops of the tallest saguaros in the dusk of evening. The lesser
nighthawk also ranges up to the oak woodlands.
[Illustration: The white-winged dove’s interest in the saguaro is in
the nectar and fruit.]
Predators are an integral part of the bird population, one of the
smallest and most active being the LOGGERHEAD SHRIKE. This
black-and-gray bird gorges itself on beetles and grasshoppers when
insects are abundant, turning to lizards, rodents, and small birds at
other times. It has the unusual habit of impaling its prey on thorns for
future use. The RED-TAILED HAWK is the commonest of the large soaring
hawks, which live mainly on rodents and reptiles. It builds its large
stick nest in the forks of saguaro arms. Like the shrike and the SPARROW
HAWK, the red-tailed hawk is found in grasslands, chaparral, and
woodlands as well as in the desert. Because of their nocturnal habits,
owls are not often seen by visitors, but they are abundant in the
monument. In addition to the GREAT HORNED OWL, which like the red-tailed
hawk feeds principally on rodents and builds cumbersome nests in saguaro
branches, the SCREECH OWL and the tiny ELF OWL are numerous in the
cactus community. Screech and elf owls make use of abandoned woodpecker
holes in saguaros, not so much for nesting as for dark and comfortable
hiding places during daylight hours; they emerge after sunset to hunt
insects and small rodents. Best known of the carrion eaters, the TURKEY
VULTURE is rarely seen on the ground, but is a common sight, singly or
in groups, circling high in the sky.
[Illustration: The red-tailed hawk builds its nest in the fork of a
saguaro and by day ranges over the entire monument in search of
prey.]
The oak-pine-juniper woodland has its set of birds too. One of the
noisiest, most quarrelsome, and most mischievous is the MEXICAN JAY, a
permanent resident. In summer, it shares this habitat with the
night-flying poor-will, which closely resembles the nighthawk but lacks
the white wing patches. Shy, secretive, and protectively colored, this
bird is rarely seen, but its plaintive call is a familiar twilight sound
at the middle elevations of the mountains. Here, too, is found the
strikingly patterned HARLEQUIN QUAIL, which waits until you are almost
upon it before flushing. The _RUFOUS-SIDED TOWHEE_ prefers brushy slopes
and canyons, where it trills its monotonous song from the branch of a
skunkbush or scratches noisily and industriously among the fallen leaves
beneath an oak. And anywhere from the oak-pine woodland to the top of
the Rincons, you are likely to startle the large BAND-TAILED PIGEON from
its perch.
The pine and fir forests of the higher Rincons are rich in bird life in
summer, but only a few species remain the year around. Among the latter
is the STELLER’S JAY, which includes insects in its summer diet but
feeds mainly on acorns and other vegetable material in winter. The
MOUNTAIN CHICKADEE is busy among the branches of the large pines and
firs even when snow lies deep on the ground. PIGMY NUTHATCHES—tiny,
constantly twittering insect-eaters—also remain all year.
[Illustration: The great horned owl, a nocturnal counterpart of the
red-tailed hawk, nests in the saguaro and feeds primarily on
rodents.]
[Illustration: Steller’s jay lives year-round in the pine and fir
forests of the higher Rincons.]
In summer, when insects are plentiful, the mountain forests are alive
with birds. The MEXICAN JUNCO, which winters at lower elevations, hides
its nest in grass clumps among the firs and aspens. Hummingbirds of
several species pause on vibrating wings to suck nectar from blossoms in
the meadow at Manning Camp. Brightly colored summer visitors such as the
HEPATIC TANAGER and the PAINTED REDSTART search for insects among the
pine boughs or flash in the sunlight as they flutter across open glades
in the forest. The mountaintops, too, have their predators; the COOPER’S
HAWK, which nests in wooded canyons, is large enough to lift a pigeon or
rabbit, but generally preys on rodents and smaller birds. The largest
bird known to inhabit the Rincon Mountains is the TURKEY, which nests
and raises its young among the firs and aspens. It descends in winter to
the oak-pine woodlands, where it feeds on pinyon nuts, acorns, and grass
seeds.
Mammals
The most frequently seen mammals in the monument are rodents and members
of the hare clan. Among the latter group are two rabbits. The DESERT
COTTONTAIL is common in the lower levels of the desert, and the EASTERN
COTTONTAIL inhabits the mountains to 8,600 feet. Adaptable to a wide
range of environmental conditions, these animals augment the water they
obtain from springs with moisture derived from sap. There are two
species of JACKRABBITS (actually hares) in the monument. They remain at
the lower levels, where they are a common sight amid the cactuses.
Unlike rabbits, which are born naked, blind, and helpless, hares are
born with fur, open eyes, and the ability to move about.
[Illustration: The Yuma (or gray-tailed) antelope ground squirrel, a
chipmunk-like rodent of the desert and grassland.]
[Illustration: In the monument, the cliff chipmunk prefers the
oak-pine woodland and the coniferous forest.]
Among the monument rodents the largest are the PORCUPINES. Though rarely
seen, they leave characteristic scars on pinyons and ponderosa pines,
recording their feeding habits at higher elevations. They are also
active in the chaparral belt, and an individual occasionally wanders
down into the desert where it eats mesquite beans and samples the bark
of ocotillos and other shrubs and trees.
Several species of ground squirrels are abundant. At the lower levels,
especially among creosotebushes, the ROUNDTAIL GROUND SQUIRREL finds
suitable living conditions, while the YUMA ANTELOPE GROUND SQUIRREL
ranges from the cactus forests into grassland. At this elevation and
upward through the pinyons and junipers, the ROCK SQUIRREL makes its
burrows in rocky ledges and brushy canyons. CLIFF CHIPMUNKS enliven the
oak-pine woodland and higher forests with their quick movements and
cheerful chatter.
KANGAROO RATS honeycomb the soil from the cactus forests up to the
oak-pine belt. Remaining underground during the day, they are frequently
seen at night. These animals do not require free water; they obtain
adequate moisture from a chemical process within the body during the
digestion of food, which is mostly dry seeds. WOODRATS, famous in song
and story as pack rats or trade rats because of their habit of carrying
away objects of human use and leaving something else in their place, are
found throughout the monument at all elevations. Look for their stick
nests among the pads of prickly pear, a favorite food.
Other rodents common in the monument include the CACTUS MOUSE,
GRASSHOPPER MOUSE, DEER MOUSE, and VALLEY POCKET GOPHER.
[Illustration: The four species of kangaroo rats found in Saguaro
look too much alike to be distinguished in the field.]
[Illustration: Mule deer.]
Among the larger mammals in the monument are two species of deer. The
MULE DEER subsists in winter on cactus fruits, ephemerals, and other
desert vegetation. In summer they find abundant browse in the higher oak
woodland. The forested areas along the crest of the Rincons support a
population of the smaller WHITETAIL DEER. These graceful animals browse
on aspen, buckbrush, and other shrubs and small trees. They are
particularly fond of acorns. When snow flies some descend to the
protective cover of the oak-pine woodlands and chaparral.
PECCARIES, characteristic of southwestern deserts, usually travel in
herds of from three to as many as 50 animals. They wander through the
groves of mesquite along desert washes, and root among beds of
pricklypear. Pricklypear pads are their chief food; they are said to
feed upon cactus fruits in summer and autumn. In addition to the
moisture obtained from succulent stems and fruits, peccaries require
considerable water, hence they frequent springs and seeps. Small bands
of these animals occasionally visit the waterhole near the visitor
center, where they are excitedly watched by visitors fortunate enough to
be in the lobby at the time.
Saguaro National Monument also has a large number of predatory animals.
Many of these, popularly believed to be exclusively meat-eaters,
actually also eat much vegetable matter. The predators—an exciting part
of the monument’s fauna—play an important role in preventing
overpopulation of the prolific rodents.
Chief among predators is the COYOTE, which ranges throughout the
monument. In winter, coyotes are found principally below 6,000 feet,
where hunting is easier and where rodents remain longer out of
hibernation. They are also known to roam the forested heights of the
Rincons and Tanque Verde Ridge. Studies of coyotes in the monument made
by biologist Lowell Sumner in January 1951 showed that their winter diet
consisted of about 78 percent fruits and seeds, 11 percent small
rodents, 7 percent deer, 4 percent birds, reptiles, insects, and
carrion, and 1 percent debris. The coyote is one of the principal wild
creatures associated with the history of the West, and its continuing
presence in the monument brings a thrill of pleasure to visitors who
hear the voices of the pack during the calm of evening, or catch a
glimpse of one of these gray canines trotting through open stands of
saguaros. BOBCATS, ranging over much the same territory as coyotes,
subsist principally on rodents, birds, and insects. Because of their
secretive habits, they are seldom seen.
[Illustration: Collared peccary, or javelina.]
The GRAY FOX is another fairly common inhabitant of the cactus desert
and higher brushlands, and is also known to roam the forested uplands.
It is usually seen at night. Rodents are its principal source of food,
but it also preys on birds and reptiles and eats much vegetable matter.
The smaller and rather rare KIT FOX, restricted mostly to the desert, is
also a night hunter. Kangaroo rats are a favorite item in the kit fox
diet, but these small predators also eat grasshoppers and other insects.
Skunks, members of the weasel family, are relatively common in the
monument, and several species inhabit areas where water is available.
They are usually active at night. The HOGNOSE SKUNK is a desert dweller
recognizable by its solid-white back. It roots for insect larvae and
eats cactus fruits, bird eggs, and nestlings. The STRIPED SKUNK ranges
throughout the monument; the SPOTTED SKUNK is found at all elevations,
usually among rocks. Insects, rodents, and fruits are its main food.
Another member of the weasel family, the BADGER, is occasionally seen in
the desert although it is by no means limited to that habitat. The
badger feeds mainly on rodents, which it digs from burrows with its
strong forelegs and heavy claws.
The RACCOON, longer-legged than the badger, is readily recognized by its
gray fur, black mask, and ambling gait. It inhabits brushy canyons
having permanent water, and sometimes wanders up into the pine belt in
summer. Amphibians, scarce as they are, and other water creatures are
among the preferred foods of raccoons; but they also eat small rodents
and plant food, including berries, acorns, and other fruits.
[Illustration: Badger.]
The RINGTAIL, a smaller relative of the raccoon, is somewhat similar in
habitat preference and nocturnal habits. Its flattened, bushy tail,
acting as a balancer, helps this short-legged, agile animal in leaping
from point to point on the steep rocky surfaces it seems to favor. It
sometimes takes up residence in little-used or abandoned buildings,
where small rodents, its principal source of food, are usually abundant.
About the size of a house cat, it has large eyes and ears and
alternating dark and light bands on its tail.
A tropical animal that seems to be extending its range northward, the
COATI (or coatimundi) is often seen in the forests of the Rincons. With
long snout and long, banded tail, it looks something like an elongated
raccoon, to which it too is related. These omnivorous animals travel in
bands, rooting among leaves for insects and whatever else they can find.
[Illustration: Coati, or coatimundi.]
[Illustration: Desert vegetation near Red Hill, Tucson Mountain
Section.]
the rhythms of nature
Natural landscapes may appear unchanging, but this is illusion. Within
the apparent constancy, daily and seasonal cycles, fluctuations in
numbers, and long-term change are the rule.
Daily cycles are obvious to those who are about at the edges of the day.
Take 24 summer hours in the cactus forest of Saguaro National Monument.
When the first light comes over the mountains, curve-billed thrashers
and cactus wrens sing noisily among the chollas. Other birds soon join
in. The early morning walker is likely to hear peccaries grunting in the
mesquites along a wash, or see mule deer staring at him, frozen like
statues before sudden flight to a sheltering thicket.
At midday, the scene is quiet. Nothing stirs under the baking sun except
perhaps a vulture, soaring on the hot air currents. The desert creatures
have not gone—they are in the shade of bushes or underground. Even some
of the plants are “taking a siesta,” having folded their leaves or
closed their leaf pores.
Soon after sundown the desert comes to life again. The birds give a
subdued version of their morning’s vocal performance. Tarantulas begin
their slow, stately walk over the ground searching for prey or mates.
Coyotes stretch and howl—a prelude to the evening’s hunt. As night
falls, rattlesnakes emerge from their cool retreats to search out
kangaroo rats, which in great numbers are scrutinizing the sand for
seeds. And through the night, creatures of many other kinds hunt food to
last them through another broiling day.
The rhythmic patterns of the daily cycle are paralleled on a larger
scale through the year—seasons of activity follow seasons of quiet. In
the desert, rain or lack of rain marks the changes, though gradually
rising or falling temperature adds its impact.
The gentle rains of winter prepare the way for the year’s greatest burst
of activity. By March, spring flowers are blooming and birds are
starting to nest. Snakes begin to come out of hibernation. April and May
see the apex of spring activity, as insects swarm around the flowering
plants, and birds take advantage of this proliferation of food to raise
their young. The desert now is yellow with the blossoms of paloverde,
mesquite, acacia, and brittlebush.
But April also marks the beginning of a drought that intensifies through
May and June, making these last 2 months the year’s parching crucible in
which reproductive ability is tested. If winter rains have been meager,
the heat and drought of May and June can kill all the young of many
birds. Some birds, such as Gambel’s quail, may not even attempt to nest
in a dry year. Conditions may be so harsh at this season that some
mammals, such as the pocket mouse, close up shop completely, sleeping
the days away underground.
Relief comes with the rains of July and August. Now the summer annuals
spring magically from the ground, perennials put forth new leaves, and
saguaros do all their growing for the year. This summer burst of plant
growth is accompanied by a new hatching of insects, which allows a few
more birds to nest, and along with the new vegetation supports a larger
pyramid of animal life generally. Among the new animals that reappear
are toads, which now emerge from their long sleep in the soil to mate
and lay eggs in the pools formed by summer rains.
When the last torrential rain of August or September falls, a new dip in
the yearly cycle of activity begins. This one is not so deep, not so
trying, as the drought of early summer, but it too is a time of relative
quiet. Roundtail squirrels go underground to sleep until cooler weather
comes. Now the migrating birds slip through, hardly noticed among the
mesquites and paloverdes. Butterflies lay their eggs, in preparation for
a new generation beyond the winter. Signaling the last phase in the
yearly cycle, wet canyons turn yellow and brown as cottonwoods, willows,
and sycamores present a pale version of the spectacular foliage displays
seen in the East.
While these daily and seasonal cycles are following their well-known
courses, each species of plant and animal is undergoing its own
fluctuations, in a constant struggle that generally goes unnoticed. For
the balance of nature is not a static one, but more like the rocking of
a seesaw on its fulcrum. The population of a species goes up one year,
down another—depending on the weather, the food supply, predators,
competitors, and a thousand interactions that reverberate through the
community in which it lives. The numbers of some species, like the
Gambel’s quail, fluctuate wildly from year to year, while those of
others, such as the harvester ant, remain quite stable. But the
oscillations of the seesaw, big and little, average out from year to
year so that the species maintains itself in the community. The other
members are going through the same thing, in a system of checks and
balances that over the short run keeps the whole community nearly
constant.
But over decades, centuries, or longer, the fulcrum of the seesaw moves:
the larger environment changes, and the community and its constituent
plants and animals must change with it or perish. Such changes may be
climatic, as we saw with the formation of the Southwestern deserts; or
it may be geologic, as with the rising and partial disintegration of the
Rincon Mountains. The efforts of plant and animal species to meet such
changes constitute in large part the story of evolution, for new
environments spawn newly evolved forms of life. Evidence of such
evolution we have seen in the plants of the Sonoran Desert, notably the
giant saguaro cactus, whose prickly ancestor lived in the West Indies
only 20,000 years ago.
Thus nature is ever-changing; and the inexorable rule for all living
things is, “adapt or perish.” Before technological man enters the scene,
the slow evolutionary process can keep pace with the changing
environments, though here and there a species is dropped by the wayside.
Generally, communities of living things reach new equilibria without
serious disruption.
But what happens when man, with his machines and his passion for
progress, institutes changes of a speed and kind and on a scale
drastically different from those brought about by earthquakes, storms,
shifting climates, and other natural phenomena? What happens to the
living things that have adapted to the harsh desert environment when
that environment is drastically altered?
[Illustration: Saguaro cactus being uprooted.]
the impact of man
Man has been a part of the scene in this region for several thousand
years, but until recent times his influence on it was minimal. Only with
the rapid technological development of the last century has man been
able to make a major impact on this landscape. Thus the story of man,
here as elsewhere, is a story of gradually accelerating power to change
environments, a power that now threatens to destroy environments, and
with them, man himself.
From carbon-14 dating in Ventana Cave, we know that man was here at
least 12,500 years ago, in the Pleistocene age, a time that was cool and
moist compared to the present. Living by hunting, he followed mammoths
and other large mammals. As the climate warmed during succeeding
millenniums, and these mammals became extinct, he came to rely more on
plant foods. These hunters and gatherers necessarily had to live in
small bands scattered over the land, since the plants and animals on
which they depended were widely dispersed. By 300 B.C., they had learned
from people to the south how to cultivate food plants, and had developed
a sedentary way of life. About 2,300 years ago a group we call the
Hohokam settled in the Salt and Gila River basins (including the Santa
Cruz Valley). By A.D. 700 they had a well developed agricultural economy
including extensive irrigation systems. Pottery fragments, projectile
points, petroglyphs (rock carvings), and other evidence show that
Hohokam villages existed for about 600 years in the eastern section of
the monument along Rincon Creek and its tributary washes. Archeological
work in the Tucson Mountain Section has indicated that this area was
visited only temporarily by the Hohokam, for hunting, food gathering,
and perhaps ceremonial purposes.
During the 15th century the Hohokam high culture vanished. Soils made
salty from irrigation water and internecine warfare are suggested
explanations.
When the Spanish explorer Coronado passed to the east of the Rincons in
1540, he found the Sobaipuri living there. The Pimas, descendants of the
Hohokam, occupied the same basins the Hohokam had. To the west, in drier
country, lived the Papago. These tribes, thought to be descendants of
the Hohokam, lived much the same sort of life, practicing irrigation
where surface water was available, hunting and gathering where it was
not.
The period of Spanish rule, implemented by a series of missions, began
in the Santa Cruz Valley about 1692, when the energetic Father Kino
began his work among the Pima and Papago. The mission system
concentrated the Indians in fewer places, brought Spanish and, later,
Mexican settlers into southern Arizona, and introduced sheep, cattle,
and goats. Although the new culture must have had some environmental
effects, there is no evidence of drastic change. Grass was plentiful,
and streams, including the Santa Cruz, remained marshy and unchanneled.
After the Gadsden Purchase of 1853-54, however, when the present
boundary with Mexico was established and this area came into United
States ownership, man’s impact on the land increased. Apache raiding had
been a deterrent to settlement during the 18th and 19th centuries, but,
after the Civil War, American soldiers got the upper hand and settlement
increased. Following completion of the Southern Pacific Railroad to
Tucson in 1879, a cattle boom began. The disastrous results of the
livestock explosion of the eighties—overgrazing, soil erosion, and
starvation of cattle—we have already seen in the story of the saguaro
cactus. In 1890, a flood cut a deep channel in the Santa Cruz River,
transforming it from a meandering, marshy stream to the usually dry
incision one sees today. The arroyo cutting of this and many other
rivers throughout the Southwest was undoubtedly due partly to increasing
aridity, which reduced the plant cover and its water-holding capacity.
But the erosion was probably triggered by overgrazing.
In the monument, we have already seen how grazing pressure, hunting, and
predator control reduced ground cover and led to an upsurge of certain
rodents and a decline in large mammals. But there have been other
man-induced changes. For as long as there has been forest on top of the
Rincons, there has been fire. Lightning-caused fire is a natural part of
ponderosa-pine forest, every few years burning the litter and small
trees and shrubs from the forest floor, and thus maintaining open stands
of tall trees. But since 1908, when the Rincon Mountains came under
protection of the Forest Service, U.S. Department of Agriculture (to be
followed in 1933 by National Park Service, U.S. Department of the
Interior protection), fires have been put out as fast as possible. This
policy has resulted in a paradox. On the one hand, thickets of scrawny
young pines and shrubs such as buckbrush have developed in many places
under the tall pines. On the other hand, the accumulation of litter and
low-level vegetation has provided fuel over the years for occasional
very hot crown fires, which have been hard to control and which have
burned large acreages. On top of the Rincons you can see several meadows
that resulted from these fires. Only a few scattered trees and stumps
remain in them to suggest the forest that once was there.
Ideally, national parks and monuments should be “vignettes of primitive
America”—naturally evolved landscapes in much the same condition as when
first seen by Europeans. In reality they are compromises—beautiful,
wild, but still bearing the marks of human occupation. In Saguaro, as we
have seen, fire control has produced a forest different from that known
to the Indians who once lived here; grazing has depleted the ground
cover; and hunting has removed the desert bighorn from its rocky haunts.
In these days of burgeoning population, when human influence is
affecting every natural landscape, environmental management becomes
necessary to approach the ideal of naturalness. This may mean
“prescribed burns” to return forests to their earlier state; elimination
of grazing; or reintroduction of animals once native to a park. In the
summer of 1971, after 2 inches of rainfall, natural burns (caused by
lightning strikes) were allowed to run their courses.
Some or all of these measures may be taken in Saguaro, in order that
future generations will know a piece of the Sonoran Desert as it was in
Coronado’s time.
The realization of this goal, however diligently we work toward it,
seems almost each day to become more difficult of attainment. These
desert and mountain environments—which once seemed secure, needing only
the continued protection afforded by their status as a national
monument—are increasingly imperiled by the works of man. As the city of
Tucson sprawls in all directions, the monument’s two divisions, islands
in an encroaching sea of civilization, must withstand ever-accelerating
hazards. Vandalism takes an increasing toll of the saguaros; housing
developments creep toward the monument borders. Smog drifts over the
fragile plant communities, threatening to choke them—as the polluted air
from Los Angeles is already strangling forests in the distant San
Bernardino Mountains.
A new awareness that the best-managed preserve cannot thrive
independently of what is happening in the surrounding region only
emphasizes the difficulty of the task. Saving the saguaros is inevitably
tied to the problem of enhancing the quality of life and reversing the
degradation of the environment—not only in Tucson but throughout the
Southwest.
There is no time to waste. Only concerted effort by scientists, resource
managers, and the community can assure that our grandchildren will be
able to visit a Saguaro National Monument where coyotes howl under the
moon, peccaries snort through the washes, and giant cactuses lift
bristly green arms into a blue sky.
appendix
Suggested Reading
Arnberger, Leslie P. _Flowers of the Southwest Mountains._ Southwestern
Monuments Association, Popular Series No. 7. Globe, Ariz. 1962.
Benson, Lyman D. _The Cacti of Arizona._ University of Arizona Press,
Tucson. 1969.
Burns, William A. (ed.). _The Natural History of the Southwest._
Franklin Watts, Inc., New York. 1960.
Dodge, Natt N. _Flowers of the Southwest Deserts._ Southwestern
Monuments Association. Popular Series No. 4. Globe, Ariz. 1961.
——. _Poisonous Dwellers of the Desert._ Southwestern Monuments
Association. Popular Series No. 3. Globe, Ariz. 1964.
Dodge, Natt N., and Herbert S. Zim. _The Southwest._ Golden Press, New
York. 1962.
Earle, W. Hubert. _Cacti of the Southwest._ Desert Botanical Garden.
Phoenix, Ariz. 1963.
Jaeger, Edmund C. _The North American Deserts._ Stanford University
Press, Stanford, Calif. 1957.
Kearney, Thomas H., Robert H. Peebles, and collaborators. _Arizona
Flora._ University of California Press, Berkeley. 1960.
Krutch, Joseph W. _The Voice of the Desert._ William Sloane Associates,
Inc., New York. 1955.
Milne, Lorus, and Margery Milne. _The Balance of Nature._ Alfred A.
Knopf, Inc., New York. 1960.
Olin, George. _Mammals of the Southwest Deserts._ Southwestern Monuments
Association, Popular Series No. 8. Globe, Ariz. 1965.
——. _Mammals of the Southwest Mountains and Mesas._ Southwestern
Monuments Association, Popular Series No. 9. Globe, Ariz. 1961.
Patraw, Pauline M. _Flowers of the Southwest Mesas._ Southwestern
Monuments Association. Popular Series No. 5. Globe, Ariz. 1959.
Phillips, Allen, Joe Marshall, and Gale Monson. _The Birds of Arizona._
University of Arizona Press, Tucson. 1964.
Schmidt-Nielsen, Knut. _Desert Animals: Physiological Problems of Heat
and Water._ Oxford University Press, Inc., New York. 1964.
Sears, Paul B. _Deserts on the March._ University of Oklahoma Press,
Norman. 1959.
Stebbins, Robert C. _Amphibians and Reptiles of Western North America._
McGraw-Hill Book Co., New York. 1954.
Storer, John H. _The Web of Life._ The Devin-Adair Co., Old Greenwich,
Conn. 1960.
Sutton, Ann, and Myron Sutton. _The Life of the Desert._ McGraw-Hill
Book Co., New York. 1966.
Underhill, Ruth. _People of the Crimson Evening._ Publications Service,
Haskell Institute, Lawrence, Kans. 1951.
Common and Scientific Names of Plants
Agave—_See_ Amole
Alligator juniper—_Juniperus deppeana_
Amole—_Agave schottii_
Arizona cypress—_Cupressus arizonica_
Arizona rosewood—_Vauquelinia californica_
Arizona sycamore—_Platanus wrightii_
Arizona white oak—_Quercus arizonica_
Aster—_Aster commutatus_
Barrel cactus—_Ferocactus wislizenii_, _F. lecontii_
Beargrass—_Nolina microcarpa_
Bladder-pod—_Lesquerella gordoni_
Bluedicks—_Dichelostemma pulchellum_
Blue paloverde—_Cercidium floridium_
Bluegrass—_Poa fendleriana_
Boxelder—_Acer negundo_
Bracken—_Pteridium aquilinum_
Brittlebush—_Encelia farinosa_
Buckbrush—_Ceanothus fendleri_
Bullgrass—_Muhlenbergia emersleyi_
Catclaw—_Acacia greggii_
Chain fruit cholla—_Opuntia fulgida_
Chihuahua pine—_Pinus chihuahuana_
Chokecherry—_Prunus virginiana_
Cinquefoil—_Potentilla subviscosa_
Cologania—_Cologania lemmoni_
Creosotebush—_Larrea tridentata_
Curly mesquitegrass—_Hilaria belangeri_
Desert chicory—_Rafinesquia neomexicana_
Desert Christmas cactus—_Opuntia leptocaulis_
Desert-marigold—_Baileya multiradiata_
Dogbane—_Apocynum androsaemifolium_
Douglas-fir—_Pseudotsuga menziesii_
Emory oak—_Quercus emoryi_
Fairy-duster—_Calliandra eriophylla_
Fiddleneck—_Amsinckia intermedia_
Filaree—_Erodium cicutarium_
Fishhook cactus—_Mammillaria sp._
Fleabane—_Erigeron arizonicus_
Gambel’s oak—_Quercus gambelii_
Goldenrod—_Solidago sparsiflora_
Goldfern—_Pityrogramma triangularis_
Gourd—_Cucurbita digitata_
Grama—_Bouteloua sp._
Groundsel—_Senecio neomexicanus_
Hairy grama—_Bouteloua hirsuta_
Hedgehog cactus—_Echinocereus sp._
Houstonia—_Houstonia wrightii_
Indian wheat—_Plantago purschii_
Indigobush—_Dalea sp._
Ironwood—_Olneya tesota_
Jointfir—_Ephedra sp._
Jojoba—_Simmondsia chinensis_
Lupine—_Lupinus sp._
Marigold—_Tagetes lemmoni_
Mesquite—_Prosopis juliflora_
Mexican blue oak—_Quercus oblongifolia_
Mexican pinyon pine—_Pinus cembroides_
Mexican white pine—_Pinus strobiforms_
Mock-pennyroyal—_Hedeoma hyssopifolium_
Mountain-mahogany—_Cercocarpus breviflorus_
Mountain muhly—_Muhlenbergia montana_
Netleaf hackberry—_Celtis reticulata_
New Mexican alder—_Alnus oblongifolia_
New Mexican locust—_Robinia neomexicana_
Nightblooming cereus—_Peniocereus greggii_
Ocotillo—_Fouquieria splendens_
Orange sneezeweed—_Helenium hoopesii_
Palmer oak—_Quercus palmeri_
Paper flower—_Psilostrophe cooperi_
Parry’s penstemon—_Penstemon parryi_
Peavine—_Lathyrus graminifolius_
Pencil cholla—_Opuntia arbuscula_
Phacelia—_Phacelia crenulata_
Pincushion cactus—_Mammillaria sp._
Pine dropseed—_Blepharoneuron tricholepis_
Pointleaf manzanita—_Arctostaphylos pungens_
Ponderosa pine—_Pinus ponderosa_
Pricklypear—_Opuntina engelmannii_ and others
Puccoon—_Lithospermum multiflorum_
Quaking aspen—_Populus tremuloides_
Sacahuista—_See_ Beargrass
Saguaro—_Carnegiea gigantea_
Scorpionweed—_Phacelia crenulata_
Screwleaf muhly—_Muhlenbergia virescens_
Shindagger—_See_ Amole
Shrub live oak—_Quercus turbinella_
Sideoats grama—_Bouteloua curtipendula_
Silktassel—_Garrya wrightii_
Silverleaf oak—_Quercus hypoleucoides_
Skunkbush—_Rhus trilobata_
Snakeweed—_Futierrezia sp._
Snowberry—_Symphoricarpos oreophilus_
Sotol—_Dasylirion wheeleri_
Spanish dagger—_Yucca schottii_
Sprucetop grama—_Bouteloua chondrosioides_
Staghorn cholla—_Opuntia versicolor_
Tanglehead—_Heteropogon contortus_
Teddy bear cholla—_Opuntia bigelovii_
Texas bluestem—_Andropogon cirratus_
Triangle bursage—_Franseria deltoidea_
Turpentine-bush—_Haplopappus laricifolius_
Vine mesquite grass—_Panicum bulbosum_
Western yarrow—_Achillea lanulosa_
White fir—_Abies concolor_
White tackstem—_Calycoseris wrightii_
Wild carrot—_Daucus pusillus_
Wild-cucumber—_Marah gilensis_
Wild-heliotrope—_Heliotropium curassavicum_
Willow—_Salix sp._
Wolfberry—_Lycium sp._
Wolftail—_Lycurus phleoides_
Yellow paloverde—_Cercidium microphyllum_
Reptiles and Amphibians of the monument.
This checklist names reptiles and amphibians that have been seen, or
that should occur, according to range maps and distribution records in
important reference works, in the monument. Four of these species are
found only in the Tucson Mountain Section; they are: desert iguana,
desert horned lizard, western shovel-nosed snake, and sidewinder. An
asterisk marks those species most commonly seen in the daytime.
The _desert_ (D) habitat is the rather flat or gently rolling terrain
below 3,200 feet in elevation, as seen in the vicinity of the visitor
center and the Cactus Forest Drive, and in the north and west portions
of the Tucson Mountain Section.
The _foothills_ (F) habitat includes the area above 3,200 feet where the
land becomes quite rocky and begins to ascend rather sharply on the
Cactus Forest Drive and along Hohokam Road in the Tucson Mountain
Section.
The _mountain_ (M) habitat is restricted to the Rincon Mountains above
an elevation of 6,500 feet where one finds tall trees.
common name scientific name habitat
AMPHIBIANS _toads and frogs_
Colorado River Toad _Bufo alvarius_ D F
Great Plains Toad _Bufo cognatus_ D
Red-spotted Toad _Bufo punctatus_ D F
Woodhouse’s Toad _Bufo woodhousei_ D F M
Couch’s Spadefoot _Scaphiopus couchi_ D F
Western Spadefoot _Scaphiopus hammondi_ D F M
Canyon Treefrog _Hyla arenicolor_ F M
Leopard Frog _Rana pipiens_ D F M
REPTILES _turtles_
*Desert Tortoise _Gopherus agassizi_ D F
Western Box Turtle _Terrapene ornata_ D F
Sonora Mud Turtle _Kinosternon sonoriense_ D F M
Spiny Softshell _Trionyx ferox_ D
_lizards_
Banded Gecko _Coleonyx variegatus_ D F
Desert Iguana _Dipsosaurus dorsalis_ D
Lesser Earless Lizard _Holbrookia maculata_ D F
Greater Earless Lizard _Holbrookia texana_ D F
*Zebra-tailed Lizard _Callisaurus draconoides_ D F
*Collared Lizard _Crotaphytus collaris_ D F
Leopard Lizard _Crotaphytus wislizenii_ D F
Short-horned Lizard _Phrynosoma douglassi_ F M
Desert Horned Lizard _Phrynosoma platyrhinos_ D
*Regal Horned Lizard _Phrynosoma solare_ D F
*Side-blotched Lizard _Uta stansburiana_ D F
*Tree Lizard _Uta ornata_ D F M
*Desert Spiny Lizard _Sceloporus magister_ D F
Clark’s Spiny Lizard _Sceloporus clarki_ D F M
Eastern Fence Lizard _Sceloporus undulatus_ F M
*Western Whiptail _Cnemidophorus tigris_ D F
Spotted Whiptail _Cnemidophorus sacki_ D F
Arizona Alligator Lizard _Gerrhonotus kingi_ M
*Great Plains Skink _Eumeces obsoletus_ D F
*Gila Monster _Heloderma suspectum_ D F
_snakes_
Western Blind Snake _Leptotyphlops humilis_ D F
Arizona Coral Snake _Micruroides euryxanthus_ D F M
Regal Ringnecked Snake _Diadophis regalis_ F M
Western Hognose Snake _Heterodon nasicus_ D F
Spotted Leaf-nosed Snake _Phyllorhynchus D F
decurtatus_
Saddled Leaf-nosed Snake _Phyllorhynchus browni_ D F
Coachwhip _Masticophis flagellum_ D F
Sonora Whipsnake _Masticophis bilineatus_ D F M
Western Patch-nosed Snake _Salvadora hexalepis_ D F
Mountain Patch-nosed Snake _Salvadora grahamiae_ M
Glossy Snake _Arizona elegans_ D F
Gopher Snake _Pituophis catenifer_ D F M
Compton Kingsnake _Lampropeltis getulus_ D F
Sonora Mountain Kingsnake _Lampropeltis pyromelana_ M
Long-nosed Snake _Rhinocheilus lecontei_ D F
Black-necked Garter Snake _Thamnophis cyrtopsis_ F M
Mexican Garter Snake _Thamnophis eques_ D
Checkered Garter Snake _Thamnophis marcianus_ D F
Western Ground Snake _Sonora semiannulata_ D F
Western Shovel-nosed Snake _Chionactis occipitalis_ D
Banded Sand Snake _Chilomeniscus cinctus_ D F
Mexican Black-headed Snake _Tantilla atriceps_ D F
Plains Black-headed Snake _Tantilla nigriceps_ D F
Sonora Lyre Snake _Trimorphodon lambda_ D F
Night Snake _Hypsiglena torquata_ D F M
Western Diamondback _Crotalus atrox_ D F
Rattlesnake
Sidewinder _Crotalus cerastes_ D
Black-tailed Rattlesnake _Crotalus molossus_ F M
Tiger Rattlesnake _Crotalus tigris_ F
Mohave Rattlesnake _Crotalus scutulatus_ D F
Arizona Black Rattlesnake _Crotalus viridis F M
cerberus_
Birds of the monument
This checklist is based entirely on written records of observations of
birds seen in the monument. Names are in accordance with A.O.U.
Checklist of North American Birds, 5th edition, 1957. (See checklist of
reptiles and amphibians for description of habitats.)
key to symbols:
D desert habitat
F foothill habitat
M mountain habitat
* species most often seen at lower elevations
s summer resident
w winter visitor
p permanent resident
t transient visitor
occurrence common name
D t White-faced Ibis
D F M s Turkey Vulture
D p Black Vulture
D w Sharp-shinned Hawk
D F M p Cooper’s Hawk
D F M p *Red-tailed Hawk
D F s Swainson’s Hawk
F M s Zone-tailed Hawk
M t Ferruginous Hawk
D F s Harris’ Hawk
D s Black Hawk
F M p Golden Eagle
D w Marsh Hawk
D t Osprey
F M p Prairie Falcon
M p Peregrine Falcon
D F p *Sparrow Hawk
F p Scaled Quail
D p *Gambel’s Quail
F M p Harlequin Quail
M p Turkey
D p Killdeer
D F M t Spotted Sandpiper
D t California Gull
F M s Band-tailed Pigeon
D p Rock Dove
D F s *White-winged Dove
D p *Mourning Dove
D p Ground Dove
D p Inca Dove
D F p Roadrunner
D F M p Screech Owl
M p Whiskered Owl
M p Flammulated Owl
D F M p Great Horned Owl
D s Elf Owl
M p Spotted Owl
M s Whip-poor-will
D F p Poor-will
D F s Lesser Nighthawk
D t Vaux’s Swift
D F M s White-throated Swift
D F M s Black-chinned Hummingbird
D F s Costa’s Hummingbird
D w Anna’s Hummingbird
M s Broad-tailed Hummingbird
M s Rufous Hummingbird
M s Rivoli’s Hummingbird
M s Blue-throated Hummingbird
D F t Broad-billed Hummingbird
M p Red-shafted Flicker
D F p *Gilded Flicker
D p *Gila Woodpecker
F M p Acorn Woodpecker
D F w Yellow-bellied Sapsucker
F M t Williamson’s Sapsucker
M p Hairy Woodpecker
D F p Ladder-backed Woodpecker
F M p Arizona Woodpecker
D s Western Kingbird
D F s Cassin’s Kingbird
D F s Wied’s Crested Flycatcher
D s *Ash-throated Flycatcher
M s Olivaceous Flycatcher
D p Black Phoebe
D p *Say’s Phoebe
M s Western Flycatcher
M s Buff-breasted Flycatcher
M s Coues’ Flycatcher
M s Western Wood Pewee
D F M t Olive-sided Flycatcher
D s Vermilion Flycatcher
M s Violet-green Swallow
D t Barn Swallow
D t Cliff Swallow
D s *Purple Martin
M p Steller’s Jay
F M p Scrub Jay
F M p Mexican Jay
M p Common Raven
D F M p White-necked Raven
M t Clark’s Nutcracker
M p Mountain Chickadee
F M p Bridled Titmouse
D p *Verdin
M p Common Bushtit
M p White-breasted Nuthatch
F t Red-breasted Nuthatch
M p Pigmy Nuthatch
M p Brown Creeper
M p House Wren
F M p Bewick’s Wren
D p *Cactus Wren
D F M p Canyon Wren
D F M p Rock Wren
D p Mockingbird
D t Bendire’s Thrasher
D p *Curve-billed Thrasher
D F p Crissal Thrasher
M p Robin
F M p Hermit Thrush
F M p Western Bluebird
D F M w Mountain Bluebird
F w Townsend’s Solitaire
F M p Blue-gray Gnatcatcher
D p Black-tailed Gnatcatcher
D w *Ruby-crowned Kinglet
D F p *Phainopepla
D F p *Loggerhead Shrike
D p Starling
M s Hutton’s Vireo
D s Bell’s Vireo
M s Solitary Vireo
M s Warbling Vireo
M t Orange-crowned Warbler
M t Nashville Warbler
M s Virginia’s Warbler
D s Lucy’s Warbler
M s Olive Warbler
D t Yellow Warbler
M s *Audubon’s Warbler
M s Black-throated Gray Warbler
F M t Townsend’s Warbler
M t Hermit Warbler
M s Grace’s Warbler
D t MacGillivray’s Warbler
D t Yellowthroat
D t Yellow-breasted Chat
M s Red-faced Warbler
D F M t *Wilson’s Warbler
M s Painted Redstart
D p House Sparrow
D t Meadowlark sp.
D s *Hooded Oriole
D F s Scott’s Oriole
D s Bullock’s Oriole
D w Brewer’s Blackbird
D F s Brown-headed Cowbird
D s Bronzed Cowbird
D F s Western Tanager
M s Hepatic Tanager
D p Cardinal
D p Pyrrhuloxia
M s Black-headed Grosbeak
D w Lazuli Bunting
M p Evening Grosbeak
M t Cassin’s Finch
D F p *House Finch
F M p Pine Siskin
D F M p Lesser Goldfinch
D w Lawrence’s Goldfinch
M p Red Crossbill
D F w Green-tailed Towhee
F M p Rufous-sided Towhee
D p *Brown Towhee
D t Lark Bunting
D F w Savannah Sparrow
D w Vesper Sparrow
D t Lark Sparrow
D F p Rufous-winged Sparrow
F p Rufous-crowned Sparrow
D F p *Black-throated Sparrow
F w Oregon Junco
F w Gray-headed Junco
M p Mexican Junco
F w Clay-colored Sparrow
F w Chipping Sparrow
D F w Brewer’s Sparrow
F p Black-chinned Sparrow
D w White-crowned Sparrow
D F w Fox Sparrow
D F w Lincoln’s Sparrow
Mammals of the monument
This checklist names mammals that have been observed, and those that,
mainly according to collection records and distribution maps in _The
Recent Mammals of Arizona_, by E. Lendell Cockrum, 1960, may occur in
the monument. One species, the desert kangaroo rat, probably occurs only
in the Tucson Mountain Section. (See checklist of reptiles and
amphibians for description of habitats.)
key to symbols:
D desert habitat
F foothill habitat
M mountain habitat
* species most often seen by visitors
habitat common name
M Vagrant Shrew
D F Gray Shrew
D F Leafnose Bat
D F Hognose Bat
D F Longnose Bat
D F Yuma Myotis
D F Cave Myotis
M Long-eared Myotis
F M Fringed Myotis
F M Long-legged Myotis
D F M California Myotis
F M Small-footed Myotis
F M Silver-haired Bat
D F M Western Pipistrel
D F M Big Brown Bat
D F Red Bat
D F M Hoary Bat
D F Western Yellow Bat
D Spotted Bat
D F M Western Big-eared Bat
D F Pallid Bat
D F M Mexican Freetail Bat
D F Pocketed Freetail Bat
D F Big Freetail Bat
D F Western Mastiff Bat
D Antelope Jackrabbit
D F *Blacktail Jackrabbit
M Eastern Cottontail
D F *Desert Cottontail
D F M Rock Squirrel
D F *Yuma Antelope Ground Squirrel
D *Roundtail Ground Squirrel
F M Cliff Chipmunk
M Tassel-eared Squirrel
M Arizona Gray Squirrel
D F M Valley Pocket Gopher
D F Silky Pocket Mouse
D F Arizona Pocket Mouse
D F Hispid Pocket Mouse
D Desert Pocket Mouse
D F Rock Pocket Mouse
D Bannertail Kangaroo Rat
D Merriam Kangaroo Rat
D Ord Kangaroo Rat
D Desert Kangaroo Rat
D F Western Harvest Mouse
D F Fulvous Harvest Mouse
D Cactus Mouse
D Merriam Mouse
D F Deer Mouse
D F White-footed Mouse
F M Brush Mouse
D F Southern Grasshopper Mouse
D F Hispid Cotton Rat
D F Whitethroat Woodrat
M Mexican Woodrat
D F M Porcupine
D F M *Coyote
D F Gray Wolf
D Kit Fox
D F M Gray Fox
M Black Bear
D F Ringtail
D F M Raccoon
M Coati
D F Badger
D F M Spotted Skunk
F Striped Skunk
D F Hooded Skunk
D F Hognose Skunk
F M Jaguar
D Jaguarundi
F M Cougar
D F M Bobcat
D F *Peccary (Javelina)
D F *Mule Deer
M Whitetail Deer
D F Bighorn
Photograph Credits
Carrico, J.: 46
Coss, Harold T., Jr.: Frontispiece, 2, 6, 8, 26, 28 right, 29 left,
31, 34 left, 37 all except bottom left, 38, 40, 41, 54, 56,
62, 63, 64, 65, 66, 68, 70, 71, 73, 74, 75, 78.
Dodge, Natt N.: 32
Hoy, William: 44
Mang, Fred E., Jr.: 24, 28 left, 34 right, 37 bottom left, 39, 67, 77.
Manley, Ray: 12
Olin, George: 10, 69, 82
Steenbergh, Warren: 35, 57
Unknown: 29 right
_“As the Nation’s principal conservation agency, the Department of the
Interior has basic responsibilities for water, fish, wildlife, mineral,
land, park, and recreational resources. Indian and Territorial affairs
are other major concerns of America’s Department of Natural Resources.”
The Department works to assure the wisest choice in managing all our
resources so each will make its full contribution to a better United
States—now and in the future._
National Park Service
U.S. DEPARTMENT of the INTERIOR
★ U. S. GOVERNMENT PRINTING OFFICE: 1972 O-456-399
[Illustration: Cover landscape.]
Transcriber’s Notes
—Retained publication information from the printed edition: this eBook
is public-domain in the country of publication.
—Relocated all image captions to be immediately under the corresponding
images, removing redundant references like ”preceding page”.
—Silently corrected a few palpable typos.
—In the text versions only, text in italics is delimited by
_underscores_.
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