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Title: The Baculum in the Chipmunks of Western North America
Author: White, John A.
Language: English
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[Transcriber's Notes: The following change has been made to the text:
Page 631, added closing parenthesis to "(genus Eutamias of California)"]
The Baculum in the Chipmunks
of Western North America
BY
JOHN A. WHITE
University of Kansas Publications
Museum of Natural History
Volume 5, No. 35, pp. 611-631, 19 figures in text
December 1, 1953
University of Kansas
LAWRENCE
1953
UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
Editors: E. Raymond Hall, Chairman, A. Byron Leonard,
and Robert W. Wilson
Volume 5, No. 35, pp. 611-631, 19 figures in text
December 1, 1953
UNIVERSITY OF KANSAS
Lawrence, Kansas
PRINTED BY
FERD VOILAND, JR., STATE PRINTER
TOPEKA, KANSAS
1953
[Illustration]
24-8968
The Baculum in the Chipmunks of Western North America
By
JOHN A. WHITE
CONTENTS
PAGE
Introduction 613
Methods, Materials, and Acknowledgments 614
Variation 614
Key to the Bacula of the Species of Eutamias of
Western North America 615
Accounts by Species 616
_Eutamias alpinus_ 616
_E. minimus_ 617
_E. townsendii_ 618
_E. sonomae_ 619
_E. amoenus_ 619
_E. dorsalis_ 620
_E. merriami_ 621
_E. quadrivittatus_ 621
_E. ruficaudus_ 622
_E. cinereicollis_ 624
_E. quadrimaculatus_ 624
_E. speciosus_ 625
_E. panamintinus_ 625
_E. umbrinus_ 626
_E. palmeri_ 627
_E. bulleri_ 627
Figures 1-19. Lateral views of bacula 629
Discussion 630
Literature Cited 631
INTRODUCTION
The baculum is the bony part of the penis. In the species of the
subgenus _Neotamias_ the proximal part of the baculum is termed the
shaft, and the distal upturned part is termed the tip. On the dorsal
side of the tip there is a longitudinal ridge termed the keel. The
proximal end of the shaft is termed the base (see fig. 19). Depending on
the species, the shaft varies from 2.11 to 5.28 mm. in length, and the
base may or may not be widened or deepened.
The purpose of this report is to: (1) Show the usefulness of the
structure of the baculum as a taxonomic character in chipmunks; and (2)
compare a classification based on the structure of the baculum with a
classification based on the structure and appearance of the skull and
skin.
METHODS, MATERIALS, AND ACKNOWLEDGMENTS
The bacula which were borrowed from the University of Michigan,
Museum of Zoology, were processed according to the method
described by Friley (1947:395-397), whereas all others were
processed according to the method described by White (1951:125).
Thus the bacula that were borrowed from the University of
Michigan, are maintained there in a separate collection, whereas
the bacula borrowed from other museums and those that are at the
University of Kansas, Museum of Natural History, are housed with
the skulls of the corresponding specimens.
All measurements of the bacula were made by means of an eyepiece
micrometer.
A total of 194 bacula were seen. All of these are in the Museum
of Natural History of the University of Kansas, unless otherwise
indicated by the following symbols:
BS United States Biological Surveys Collection.
CN Chicago Natural History Museum.
LA Los Angeles County Museum.
MM University of Michigan, Museum of Zoology.
NM United States National Museum.
UU University of Utah, Museum of Zoology.
I am grateful to Professor E. Raymond Hall for guidance in my
study and thank Drs. Robert W. Wilson, Keith R. Kelson, and
Edwin C. Galbraith, as well as other friends and associates of
the Museum of Natural History, University of Kansas, for
encouragement and valuable suggestions. Dr. William L. Jellison,
United States Public Health Service, aided me in part of my
field work and kindly sent me some specimens of chipmunks. My
wife, Alice M. White, made the illustrations and helped me in
many ways.
For the loan of bacula I thank Dr. William H. Burt, University
of Michigan, Museum of Zoology. For permission to search for
bacula on study skins, and to process those that were found, I
thank Miss Viola S. Schantz, United States Fish and Wildlife
Service, Mr. Colin C. Sanborn, Chicago Natural History Museum,
Mr. Kenneth E. Stager, Los Angeles County Museum, Dr. David H.
Johnson, United States National Museum, and Dr. Stephen D.
Durrant, Museum of Zoology, University of Utah.
Assistance with field work is acknowledged from the Kansas
University Endowment Association, the National Science
Foundation and the United States Navy, Office of Naval Research,
through contract No. NR 161 791.
VARIATION
_Individual variation._--Individual variation is small. This is shown by
a coefficient of variability of only 3.85 in the length of the shaft in
a series of 12 specimens of _E. umbrinus umbrinus_ from Paradise Park,
21 mi. W and 15 mi. N Vernal, 10,050 ft., Uintah County, Utah.
_Variation with age._--In the chipmunks the baculum varies but little
with age. In the youngest specimens that I have taken, the M3 and m3
have not yet erupted and there is no wear on P4 and p4; nevertheless,
the baculum in these specimens has nearly an adult configuration and
size. In juvenal _Eutamias minimus_ the tip of the baculum is longer in
relation to the length of the shaft than it is in adults; the tip is 18
to 28 per cent of the length of the shaft in adults, as opposed to 29 to
32 per cent in juveniles.
_Aberrations._--In a small percentage of specimens of _E. minimus_ and
_E. umbrinus_ the baculum is small and S-shaped, even in adults.
_Variations of taxonomic worth._--Variations in this category are
described in the section immediately following the key.
KEY TO THE BACULA IN EUTAMIAS OF WESTERN NORTH AMERICA
1. Distal 1/2 to 2/3 of shaft markedly compressed laterally; base
markedly widened.
2. Distal 1/2 of shaft laterally compressed and curved downward
to base of tip.
3. Height of keel 1/2 of length of tip; keel markedly
enlarged. _Eutamias bulleri_, p. 627
3'. Height of keel 1/4 of length of tip; keel not markedly
enlarged.
_Eutamias umbrinus_ and _E. palmeri_, pp. 626, 627
2'. Distal 2/3 of shaft laterally compressed and curved downward
to base of tip.
4. Base of keel 1/3 of length of tip; angle formed by tip
and shaft less than 100° _Eutamias speciosus_, p. 625
4'. Base of keel 1/2 of length of tip; angle formed by tip
and shaft more than 102° _Eutamias panamintinus_, p. 625
1'. Distal 1/12 to 2/5 of shaft slightly compressed laterally; base
not markedly widened.
5. Shaft thin; shaft less than .20 mm. in diameter at widest
point.
6. Ridges on either side of keel enlarged, partially
obscuring lateral view of keel; height of keel 1/10 of
length of tip. _Eutamias sonomae_, p. 619
6'. Ridges on either side of tip not enlarged, not partially
obscuring lateral view of keel; height of keel at least
1/7 of length of tip.
7. Base not widened or dorsoventrally thickened.
8. Shaft more than 4.5 mm. in length; tip 16 per
cent of length of shaft; shaft strongly incised
on dorsal side of base
_Eutamias merriami_, p. 621
8'. Shaft less than 4.4 mm. in length; tip more than
25 per cent of length of shaft; shaft not incised
on dorsal side of base.
9. Height of keel 1/7 of length of tip; angle
formed by tip and shaft distinct
_Eutamias alpinus_, p. 616
9'. Height of keel at least 1/5 of length of tip;
angle formed by tip and shaft poorly defined.
10. Height of keel 1/3 of length of tip;
angle formed by tip and shaft 140°
_Eutamias dorsalis_, p. 620
10'. Height of keel 1/5 of length of tip;
angle formed by tip and shaft 130° or
less.
11. Tip more than 29 per cent of length
of shaft. _Eutamias amoenus_, p. 619
11'. Tip less than 28 per cent of length
of shaft. _Eutamias minimus_, p. 617
7'. Base widened and dorsoventrally thickened.
_Eutamias townsendii_, p. 618
5'. Shaft thick; shaft more than .25 mm. in diameter at widest
point.
12. Length of shaft less than 3.00 mm.; length of tip less
than 1.10 mm. _Eutamias quadrivittatus hopiensis_, p. 622
12'. Length of shaft more than 3.10 mm.; length of tip more
than 1.15 mm.
13. Tip less than 28 per cent of length of shaft.
_Eutamias quadrimaculatus_, p. 624
13'. Tip more than 29 per cent of length of shaft.
14. Angle formed by tip and shaft more than 140°;
ridges on either side of tip indistinct.
_Eutamias cinereicollis_, p. 624
14'. Angle formed by tip and shaft less than 135°;
ridges on either side of tip distinct.
15. Shaft less than 3.65 mm. in length, and .55
mm. or less in diameter at widest point.
_Eutamias quadrivittatus quadrivittatus_, p. 621
15'. Shaft usually more than 3.65 mm. in length,
but when shorter, diameter is .60 mm. or more
at widest point.
16. Diameter of shaft at widest point less
than .58 mm.; tip less than 35 per cent
of length of shaft.
_Eutamias ruficaudus ruficaudus_, p. 622
16'. Diameter of shaft at widest point more
than .65 mm.; tip more than 40 per cent
of length of shaft.
_Eutamias ruficaudus simulans_, p. 623
ACCOUNTS BY SPECIES
#Eutamias alpinus# (Merriam)
Figure 1
Pelage silky; tail bright orange beneath; markings relatively
obscure; size small; skull broad, flattened, and large in
proportion to body.
Baculum: Shaft thin; keel low, 1/7 of length of tip; tip 39 per cent of
length of shaft; angle formed by tip and shaft 135°; distal 1/3 of shaft
slightly compressed laterally; base slightly wider than shaft; shaft
short, 2.17 mm.
Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_, in base not markedly widened, and shaft
thinner; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_,
and _E. quadrimaculatus_, in shaft thinner, baculum shorter; from _E.
townsendii_, in base not dorsoventrally thickened, base not so widened;
from _E. sonomae_, in ridges on either side of tip not enlarged, base
not dorsoventrally thickened; from _E. amoenus_, _E. minimus_, and _E.
dorsalis_, in keel lower, angle formed by tip and shaft more distinct;
from _E. merriami_, in baculum markedly shorter, base not incised
dorsally.
_Specimen examined_: One from Big Cottonwood Meadows, S of Mount
Whitney, 10,000 ft., Inyo Co., California (CN).
#Eutamias minimus# (Bachman)
Figure 2
Coloration varying from light to dark depending on subspecies;
size small to medium; rostrum short and stout.
Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 18 to 28 per
cent of length of shaft; angle formed by tip and shaft 125°; distal 1/2
of shaft slightly compressed laterally; shaft short to long, 2.44 to
4.35 mm.
Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_, in shaft thinner, base not markedly widened;
from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E.
quadrimaculatus_, in shaft thinner, tip shorter; from _E. amoenus_, in
tip less than 28 per cent of length of shaft; from _E. dorsalis_, in
angle formed by tip and shaft smaller; from _E. townsendii_, in tip less
than 28 per cent of length of shaft, angle formed by tip and shaft 125°
instead of 130°; from _E. sonomae_, in ridges on either side of tip less
well-developed, keel higher; from _E. merriami_, in shaft shorter (less
than 4.40 mm.), base not incised, tip proportionally longer.
For comparison with _E. alpinus_ see the account of that species.
In most places where _E. minimus_ and _E. amoenus_ occur together they
can be distinguished without recourse to the baculum, but at Banff and
Canmore in western Alberta, recourse to the baculum is almost necessary.
There, as elsewhere, they can be distinguished readily by the shape of
the bacula.
_Specimens examined_: 72.
_Eutamias minimus borealis_: Alberta: Canmore, 1 (BS).
_E. m. cacodemus_: South Dakota: _Shannon Co._: Quinn's Draw,
Cheyenne River, 1 (NM); 14 mi. N and 5 mi. W Rockyford, 3,200
ft., 1.
_E. m. confinis_: Wyoming: _Big Horn Co._: 17 mi. E and 3 mi. S
Shell, 9,000 ft., 1; 9 mi. E and 9 mi. N Tensleep, 8,200 ft., 1.
_Washakie Co._: 9 mi. E and 4 mi. N Tensleep, 7,000 ft., 1.
_E. m. consobrinus_: Montana: _Madison Co._: 26 mi. NW West
Yellowstone, 6,100 ft., 1. Wyoming: _Sublette Co._: 5 mi. E and
9 mi. N Pinedale, 9,100 ft., 2. _Uinta Co._: 10 mi. S and 1 mi.
W Robertson, 8,700 ft., 1; 13 mi. S and 2 mi. E Robertson, 9,200
ft., 2. Utah: _Uintah Co._: Paradise Park, 21 mi. W and 15 mi. N
Vernal, 10,050 ft., 8. Colorado: _Jackson Co._: 9-1/2 mi. W and
2 mi. N Walden, 8,400 ft., 1.
_E. m. jacksoni_: Michigan: _Menominee Co._: 7 mi. E Stephenson,
4 (MM). Wisconsin: _Juneau Co._: Camp Douglas, 1 (NM).
_E. m. minimus_: Wyoming: _Natrona Co._: 27 mi. N and 1 mi. E
Powder River, 6,075 ft., 1; 16 mi. S and 11 mi. W Waltman, 6,950
ft., 1; Sun Ranch, 5 mi. W Independence Rock, 6,000 ft., 1.
_Uinta Co._: 8-1/2 mi. W Ft. Bridger, 7,100 ft., 1; 2 mi. W Ft.
Bridger, 6,700 ft., 1; unspecified, 3 (MM). _Sweetwater Co._:
Kinney Ranch, 21 mi. S Bitter Creek, 6,800 ft., 1; 32 mi. S and
22 mi. E Rock Springs, 7,025 ft., 3; 33 mi. S Bitter Creek, 1.
_E. m. operarius_: Wyoming: _Converse Co._: 21-1/2 mi. S and
24-1/2 mi. W Douglas, 1. _Carbon Co._: 8 mi. N and 19-1/2 mi. E
Savery, 8,800 ft., 1; 5 mi. N and 5 mi. E Savery, 6,900 ft., 1.
_Albany Co._: 3 mi. ESE Browns Peak, 10,000 ft., 1. Colorado:
_Rocky Mountain National Park_, 1 (MM). _Boulder Co._:
Unspecified, 1 (NM). _Gunnison Co._: 7 mi. S and 7 mi. W
Gunnison, 8,150 ft., 1. _Saguache Co._: 5 mi. N and 22 mi. W
Saguache, 10,000 ft., 2. _Archuleta Co._: Unspecified, 1 (MM); 5
mi. S and 25 mi. W Antonito, 9,600 ft., 3. _Costilla Co._:
Unspecified, 1 (MM). New Mexico: _Taos Co._: 23 mi. S and 6 mi.
E Taos, 8,750 ft., 3.
_E. m. pallidus_: Montana: _Fergus Co._: Unspecified, 1 (MM).
_Sweetgrass Co._: Unspecified, 1 (MM). Wyoming: _Campbell Co._:
4 mi. S and 3 mi. W Rockypoint, 1; Ivy Creek, 8 mi. W and 5 mi.
N Spotted Horse, 3; Middle Butte, 6,010 ft., 38 mi. S and 19 mi.
W Gillette, 1.
_E. m. silvaticus_: South Dakota: _Pennington Co._: Unspecified,
1 (MM). _Custer Co._: Unspecified, 2 (MM). Wyoming: _Weston
Co._: 1-1/2 mi. E Buckhorn, 6,150 ft., 3.
#Eutamias townsendii# (Bachman)
Figure 3
Pelage tawny to olivaceous; stripes obscure and underparts
tawny, or stripes conspicuous and underparts white; tail slender
and sparsely haired; size large; skull largest in the subgenus
_Neotamias_.
Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 32 per cent of
length of shaft; angle formed by tip and shaft 130°; distal 1/5 of shaft
slightly compressed laterally; base deeper and wider than shaft; shaft
short, 2.24 mm.
Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_, in base not markedly widened, shaft thinner,
tip proportionally shorter; from _E. quadrivittatus_, _E. ruficaudus_,
_E. cinereicollis_, and _E. quadrimaculatus_, in shaft thinner, baculum
shorter and smaller; from _E. sonomae_, in ridges on either side of tip
not enlarged, keel proportionally higher; from _E. amoenus_ and _E.
dorsalis_, in base widened and thickened, baculum usually shorter; from
_E. merriami_, in being markedly shorter, and having base widened and
deepened but not incised dorsally.
For comparisons with _E. alpinus_ and _E. minimus_ see the accounts of
those species.
_Specimens examined_: 2.
_E. townsendii townsendii_: Oregon: _Multnomah Co._: Portland, 1
(NM).
_E. t. cooperi_: Oregon: _Hood Co._: Brooks Meadow, 4,300 ft., 9
mi. ENE Mount Hood, 1.
#Eutamias sonomae# Grinnell
Figure 4
Upper parts rich reddish, more or less dulled by gray; backs of
pinnae of ears nearly bare; tail long and bushy; size large;
skull large, long, and narrow; rostrum deep.
Baculum: Shaft thin; keel low, 1/10 of length of tip; tip 27 to 31 per
cent of length of shaft; angle formed by tip and shaft 130°; distal 1/4
of shaft slightly compressed laterally; base deeper and wider than
shaft; shaft of medium length, 3.03 to 3.30 mm.; ridges on either side
of tip strongly developed, partly obscuring keel from side.
Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_, in ridges on either side of tip strongly
developed, shaft thin, base not markedly widened, tip proportionally
shorter; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_,
and _E. quadrimaculatus_, in shaft thin, ridges on either side of tip
strongly developed, baculum shorter; from _E. amoenus_ and _E.
dorsalis_, in keel lower, ridges on either side of tip strongly
developed, base thicker and wider; from _E. merriami_, in markedly
shorter, ridges on either side of tip strongly developed, tip
proportionally longer, base wider and deeper but not incised dorsally.
For comparisons with _E. alpinus_, _E. minimus_, and _E. townsendii_,
see the accounts of those species.
_Specimens examined_: 5.
_E. sonomae alleni_: California: _Marin Co._: Unspecified, 1
(NM).
_E. sonomae sonomae_: California: _Siskiyou Co._: Salmon Mts., W
slope, W of Etna, 1 (BS). _Shasta Co._: Redding, 1 (BS).
_Mendocino Co._: Cahto, 1 (BS).
#Eutamias amoenus# (J. A. Allen)
Figure 5
Upper parts generally ochraceous; venter frequently buffy; size
small to medium; zygomatic arches usually appressed to cranium;
frequently difficult to distinguish from _E. minimus_.
Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 30 to 35 per
cent of length of shaft; angle formed by tip and shaft 130°; distal 1/5
of shaft slightly compressed laterally; shaft short, 2.37 to 2.96 mm.
Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_, in base not markedly widened, shaft thinner;
from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_ and _E.
quadrimaculatus_, in shaft thinner, baculum usually shorter, tip
shorter; from _E. dorsalis_, in keel lower, angle formed by tip and
shaft 130°, usually smaller; from _E. merriami_, in being markedly
shorter, and in base not being dorsally incised, tip proportionally
longer.
For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, and
_E. sonomae_, see the accounts of those species.
Bacula from skins labeled as _E. amoenus amoenus_ from, Lardo, Valley
Co., Idaho (MM), Butte Co., Idaho (MM), and Boise National Forest, Idaho
(BS), resemble the bacula of _E. umbrinus_, and critical study of other
features of these specimens probably will show that they are _E.
umbrinus_.
_Specimens examined_: 23.
_E. amoenus amoenus_: Oregon: _Klamath Co._: Fort Klamath, 1
(MM). Idaho: _Valley Co._: Lardo, 1 (BS). _Butte Co._:
Unspecified, 1 (MM). Boise National Forest, 1 (BS).
_E. a. ludibundus_: British Columbia: Moose Lake, 1 (NM).
_E. a. luteiventris_: Alberta: Banff, 2 (BS). Montana: _Flathead
Co._: 1 mi. W and 2 mi. S Summit, 5,000 ft., 1. _Teton Co._:
17-1/8 mi. W and 6-1/2 mi. N Augusta, 5,100 ft., 2. _Missoula
Co._: Unspecified, 1 (MM). Idaho: _Idaho Co._: 20 mi. S and 2
mi. E Grangeville, 2. _Fremont Co._: 7 mi. W West Yellowstone,
7,000 ft., 5; 9 mi. SW West Yellowstone, 8,500 ft., 1. Wyoming:
_Teton Co._: 2-1/2 mi. N and 3-1/2 mi. E Moran, 7,225 ft., 1.
_E. a. monoensis_: California: _Mono Co._: Leevining Creek, 1
(NM).
_E. a. vallicola_: Montana: _Ravalli Co._: Bass Creek, 3-1/2 mi.
NW Stevensville, 3,750 ft., 2.
#Eutamias dorsalis# (Baird)
Figure 6
General tone of upper parts smoky gray; dorsal stripes
indistinct or obsolete; skull large.
Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 29 to 40 per
cent of length of shaft; angle formed by tip and shaft 140°; distal 1/2
of shaft slightly compressed laterally; shaft short to medium, 2.64 to
3.69 mm.
Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_, in base not widened, shaft thinner; from _E.
quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E.
quadrimaculatus_, in shaft thinner, baculum usually shorter; from _E.
merriami_, in shaft markedly shorter, base not incised dorsally, tip
proportionally longer.
For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E.
sonomae_, and _E. amoenus_, see the accounts of those species.
_Specimens examined_: 12.
_E. dorsalis dorsalis_: Arizona: _Yavapai Co._: 3 mi. N Ft.
Whipple, 5,000 ft., 1 (BS). _Gila Co._: Carr's Ranch, Sierra
Ancha Mountains, 1 (BS). _Pima Co._: Unspecified, 1 (MM). New
Mexico: _Valencia Co._: Mount Taylor, 1 (MM); 1 mi. N Cebolleta,
1 (MM). _Socorro Co._: San Mateo Mountains, 1 (BS). _Chihuahua_:
Sierra Madre, near Guadalupe y Calvo, 3 (BS).
_E. d. utahensis_: Wyoming: _Sweetwater Co._: W side Green
River, 1 mi. N Utah Border, 1. Colorado: _Moffat Co._: Escalante
Hills, 20 mi. SE Ladore, 1 (BS). Arizona: _Coconino Co._: Ryan,
1 (BS).
#Eutamias merriami# (J. A. Allen)
Figure 7
General tone of upper parts grayish; cheeks and underparts
white, more or less dulled by gray; size large; skull large.
Baculum: Shaft thin; keel low, 2/5 of length of tip; tip 16 per cent of
length of shaft; angle formed by tip and shaft 130°; distal 1/10 of
shaft slightly compressed laterally; base incised dorsally; shaft
markedly long, 4.88 mm.
Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_, in base incised dorsally, base not widened,
shaft thinner, tip proportionally shorter; from _E. quadrivittatus_, _E.
ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in base
incised dorsally, shaft thinner, tip proportionally much shorter.
For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E.
sonomae_, _E. amoenus_, and _E. dorsalis_, see the accounts of those
species.
_Specimens examined_: One from Mount Piños, Ventura Co.,
California (LA).
#Eutamias quadrivittatus# (Say)
Figures 8-10
Color bright and tawny; size medium to large; braincase widened.
Baculum of _E. q. quadrivittatus_: Shaft thick; keel proportionally low,
1/4 of length of tip; tip 30 to 44 per cent of length of shaft; angle
formed by tip and shaft 130°; distal 1/3 of shaft slightly compressed
laterally; shaft long, 3.17 to 3.62 mm.
Differs from _E. q. hopiensis_, in baculum larger, angle formed by tip
and shaft less distinct; from _E. ruficaudus ruficaudus_, in shaft and
tip proportionally shorter; from _E. r. simulans_, in keel
proportionally lower, shaft usually shorter and narrower; from _E.
cinereicollis_, in shaft shorter, angle formed by tip and shaft larger,
ridges on either side of tip more distinct; from _E. quadrimaculatus_,
in tip proportionally shorter, shaft shorter; from _E. speciosus_, _E.
panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base
not markedly widened, shaft longer, angle formed by tip and shaft
larger.
For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E.
sonomae_, _E. amoenus_, _E. dorsalis_, and _E. merriami_, see the
accounts of those species.
Baculum of _E. q. hopiensis_: Shaft thick; keel proportionally low, 1/3
of length of tip; tip 34 per cent of length of shaft; angle formed by
tip and shaft 130°; distal 1/3 of shaft slightly compressed laterally;
shaft short, 2.64 mm. in length.
Differs from _E. ruficaudus ruficaudus_, _E. r. simulans_, _E.
cinereicollis_, and _E. quadrimaculatus_, in being shorter, proportions
as in _E. q. quadrivittatus_; from _E. speciosus_, _E. panamintinus_,
_E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not markedly
widened, angle formed by tip and shaft larger; from _E. alpinus_, _E.
minimus_, _E. townsendii_, _E. sonomae_, _E. amoenus_, _E. dorsalis_,
and _E. merriami_, except for smaller size, as in _E. q.
quadrivittatus_.
Bacula of _E. q. hopiensis_ from northeastern Arizona are like those in
typical _E. q. quadrivittatus_. The specimens from this region, to judge
from parts of the animal other than the baculum, are intergrades between
_E. q. hopiensis_ and _E. q. quadrivittatus_. Specimens from near Moab,
Grand Co., Utah, are typical _E. q. hopiensis_ and the bacula of these
specimens are considerably smaller than those of specimens of typical
_E. q. quadrivittatus_. No bacula are known to me that are structurally
intermediate between those of _E. q. quadrivittatus_ and _E. q.
hopiensis_.
_Specimens examined_: 21.
_E. quadrivittatus quadrivittatus_: Colorado: _Gunnison Co._:
Sapinero, 1 (BS). _Chaffee Co._: Unspecified, 1 (MM). _Saguache
Co._: 5 mi. N and 22 mi. W Saguache, 10,000 ft., 1. _Fremont
Co._: Canon City, 3 (BS). New Mexico: _Rio Arriba Co._: Dulce, 1
(BS). _Taos Co._: 23 mi. S and 6 mi. E Taos, 8,750 ft., 4.
_Union Co._: Sierra Grande, 1 (BS). _Valencia Co._: Mirror
Spring, Mt. Taylor, 3 (MM). _Torrance Co._: S end, E slope,
Manzano Mountains, 2 (BS).
_E. quadrivittatus hopiensis_: Utah: _Grand Co._: Mouth of
Nigger Bill Canyon, E side Colorado River, 4 mi. N Moab Bridge,
4,500 ft., 1 (UU); Moab, 4,500 ft., 1 (UU). Arizona: _Apache
Co._: Tunicha Mountains, 1 (BS).
#Eutamias ruficaudus# Howell
Figures 11-12
General tone of upper parts dark tawny; size medium; braincase
narrowed.
Baculum of _E. r. ruficaudus_: Shaft thick; keel proportionally low, 1/4
of length of tip; tip 31 to 33 per cent of length of shaft; angle
formed by tip and shaft 120°; distal 2/5 of shaft slightly compressed
laterally; base slightly widened; shaft long, 4.09 to 4.56 mm.
Differs from _E. r. simulans_, in keel proportionally lower, tip
proportionally shorter, distal 1/5 of shaft less laterally compressed,
shaft usually longer; from _E. cinereicollis_, in angle formed by tip
and shaft smaller, shaft shorter, ridges on either side of tip distinct;
from _E. quadrimaculatus_, in tip proportionally longer, shaft usually
shorter; from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_, in base not markedly widened, shaft longer,
angle formed by tip and shaft larger.
For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E.
sonomae_, _E. amoenus_, _E. dorsalis_, _E. merriami_, and _E.
quadrivittatus_, see the accounts of those species.
Baculum of _E. r. simulans_: Shaft thick; keel proportionally low, 2/5
of length of tip; tip 40 to 48 per cent of length of shaft; angle formed
by tip and shaft 130°; distal 2/5 of shaft laterally compressed; base
slightly wider than shaft; shaft medium to long, 3.30 to 4.26 mm.
Differs from _E. cinereicollis_ in, keel proportionally higher, shaft
shorter, tip proportionally longer, angle formed by tip and shaft
smaller, distal 2/5 of shaft more laterally compressed; from _E.
quadrimaculatus_ in, keel proportionally higher, angle formed by tip and
shaft larger, tip proportionally longer, distal 2/5 of shaft more
laterally compressed, shaft shorter; from _E. speciosus_, _E.
panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base
not markedly widened, shaft usually longer.
For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E.
sonomae_, _E. amoenus_, _E. dorsalis_, _E. merriami_, and _E.
quadrivittatus_, see the accounts of those species.
The differences between the bacula of the subspecies _Eutamias
ruficaudus ruficaudus_ and _E. r. simulans_ are comparable to those
usually found between species of chipmunks. Consequently, I suspect that
_E. r. simulans_ and _E. r. ruficaudus_ are specifically distinct and
suggest that a search would be worth while for specimens in the
geographic area between the geographic ranges as now known for the two
kinds to ascertain whether intergradation (the criterion of subspecies)
occurs. I suppose there is no intergradation but in the absence of
precise information, I choose not to modify the current taxonomic
arrangement of _E. r. ruficaudus_ and _E. r. simulans_.
_Specimens examined_: 17.
_E. ruficaudus ruficaudus_: Montana: _Flathead Co._: 1 mi. W and
2 mi. S Summit, 5,000 ft., 2. _Ravalli Co._: Big Hole Hill,
6,000 ft., 2; Big Hole Hill, 6,600 ft., 1; Continental Divide,
Big Hole Hill, 7,000 ft., 1.
_E. r. simulans_: Idaho: _Bonner Co._: Priest Lake, 1 (BS).
_Kootenai Co._: 13 mi. E and 5 mi. N Coeur d'Alene, 3. _Shoshone
Co._: Mullan, 1 (BS). _Clearwater Co._: 25 mi. E and 16 mi. N
Pierce, 6.
#Eutamias cinereicollis# (J. A. Allen)
Figure 13
General tone of upper parts dark grayish tawny; size medium to
large; skull large; braincase widened.
Baculum: Shaft thick; keel proportionally low, 1/5 of length of tip; tip
34 per cent of length of shaft; angle formed by tip and shaft 145°;
distal 1/3 of shaft slightly compressed laterally; base slightly
widened; shaft long, 4.88 mm.
Differs from _E. quadrimaculatus_, in keel lower, ridges on either side
of tip weakly developed, angle formed by tip and shaft larger; from _E.
speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E.
bulleri_, in shaft longer, base not markedly widened, angle formed by
tip and shaft much larger.
For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E.
sonomae_, _E. amoenus_, _E. dorsalis_, _E. merriami_, _E.
quadrivittatus_, and _E. ruficaudus_, see the accounts of those species.
_Specimen examined_: One from Mount Thomas, White Mountains,
Apache Co., Arizona (BS).
#Eutamias quadrimaculatus# (Gray)
Figure 14
General tone of upper parts bright reddish; pattern
inconspicuous; light and dark facial stripes strongly
contrasting; size large; skull relatively small and slightly
built.
Baculum: Shaft thick; keel relatively low, 1/4 of length of tip; tip 27
per cent of length of shaft; angle formed by tip and shaft 120°; distal
1/3 of shaft slightly compressed laterally; base slightly wider than
shaft; shaft long, 4.35 to 5.28 mm.
Differs from _E. speciosus_, _E. panamintinus_, _E. townsendii_, _E.
umbrinus_, _E. palmeri_, and _E. bulleri_, in shaft markedly longer;
base not markedly widened; angle formed by tip and shaft larger; tip
proportionally shorter.
For comparisons with all other species of chipmunks from western North
America, see the accounts of those species.
_Specimens examined_: 4.
California: _Plumas Co._: Mountains near Quincy, 1 (BS). _Placer
Co._: Blue Canyon, 1 (NM). _Alpine Co._: Markleeville, 1 (BS); N
fork Stanislaus River, 1 (BS).
#Eutamias speciosus# (Merriam)
Figure 15
General tone of upper parts bright; light and dark elements of
color pattern strongly contrasting; outer stripes broad and
strikingly conspicuous; size medium; skull moderately broadened;
dorsal outline of skull strongly arched in profile; upper
incisors short and sharply recurved.
Baculum: Shaft thick; keel of medium height, 1/3 of length of tip; base
of keel 1/3 of length of tip; tip 47 to 55 per cent of length of shaft;
angle formed by tip and shaft 90°; distal 2/3 of shaft markedly
compressed laterally; base markedly wider than shaft; shaft short to
medium, 2.11 to 3.17 mm.
Differs from _E. panamintinus_, in base of keel proportionally shorter,
angle formed by tip and shaft smaller; from _E. umbrinus_ and _E.
palmeri_, in keel higher, angle formed by tip and shaft smaller, distal
2/3 (not 1/2) of shaft markedly laterally compressed, base markedly
wider; from _E. bulleri_, in keel smaller, shaft shorter, tip
proportionally longer, ridges on either side of tip distinct.
For comparisons with all other species of chipmunks of western North
America, see the accounts of those species.
The baculum in _E. speciosus frater_ is approximately the same size as
in _E. umbrinus inyoensis_, but differs in shape as described above.
_Specimens examined_: 6.
_E. speciosus frater_: California: _Madera Co._: San Joaquin
River, near head of N fork, Sierra Nevada Mountains, 2 (BS).
_E. speciosus sequoiensis_: California: _Tulare Co._: Mount
Whitney, 1 (BS); Sequoia National Park, 2 (BS).
_E. speciosus callipeplus_: California: _Kern Co._: Mount Pinos,
1 (BS).
#Eutamias panamintinus# (Merriam)
Figure 16
Dorsal dark stripes reddish; size small to medium; skull of
medium size; braincase flattened.
Baculum: Shaft thick; keel low, 1/3 of length of tip; base of keel 1/2
of length of tip; tip 52 per cent of length of shaft; angle formed by
tip and shaft 110°; distal 2/3 of shaft moderately compressed laterally;
base markedly widened; shaft short, 2.17 mm.
Differs from _E. umbrinus_ and _E. palmeri_, in distal 2/3 (rather than
1/2) of shaft moderately compressed laterally; from _E. bulleri_, in
keel smaller, shaft shorter, ridges on either side of tip distinct.
For comparisons with other species of chipmunks of western North
America, see the accounts of those species.
The structure of the baculum most closely resembles that of _E.
speciosus_ and the geographic ranges of these two species are in
juxtaposition.
_Specimen examined_: One from Coal Kilns, Panamint Mountains,
Inyo Co., California (CN).
#Eutamias umbrinus# (J. A. Allen)
Figures 17-18
General tone of upper parts dark; size medium to large; skull of
medium size; braincase narrowed.
Baculum: Shaft thick; keel low, 1/4 of length of tip; tip 36 to 50 per
cent of length of shaft; angle formed by tip and shaft 100°; distal 1/2
of shaft markedly compressed laterally; base markedly widened; shaft
short to medium, 2.51 to 3.03 mm.
Differs from _E. bulleri_, in shaft shorter, keel smaller, ridges on
either side of tip distinct; distal 1/2 of shaft strongly compressed
laterally. Does not differ from _E. palmeri_.
For comparisons with all other species of chipmunks of western North
America, see the accounts of those species.
Specimens of _E. umbrinus montanus_ from north-central Colorado have, in
the past (Howell 1929:82), been referred to _E. quadrivittatus
quadrivittatus_. In many features these two kinds of chipmunks resemble
each other closely; their bacula, nevertheless, differ markedly (compare
figs. 8-9 with 17-18).
_Specimens examined_: 25.
_E. umbrinus umbrinus_: Wyoming: _Uinta Co._: 10 mi. S and 1 mi.
W Robertson, 8,700 ft, 1. Utah: _Uintah Co._: Paradise Park, 21
mi. W and 15 mi. N Vernal, 10,050 ft., 12.
_E. u. adsitus_: Utah: _Beaver Co._: Britts Meadow, Beaver Range
Mountains, 8,500 ft, 1 (BS). _Wayne Co._: Donkey Lake, Boulder
Mountain, 10,000 ft., 1 (UU). _Garfield Co._: Wildcat R. S.,
Boulder Mountain, 8,700 ft., 1 (UU).
_E. u. sedulus_: Utah: _Garfield Co._: Mount Ellen, Henry
Mountains, 1 (BS).
_E. u. inyoensis_: California: _Tulare Co._: Mount Whitney, head
of Big Cottonwood Creek, 2 (BS). Nevada: _Elko Co._: W side Ruby
Lake, 3 mi. N Elko County Line, 1.
_E. u. nevadensis_: Nevada: _Clark Co._: Sheep Mountains, 1
(MM).
_E. u. fremonti_: Wyoming: _Sublette Co._: 31 mi. N Pinedale,
8,025 ft., 1; 19 mi. W and 2 mi. S Big Piney, 1.
_E. u. montanus_: Colorado: _Boulder Co._: 3 mi. S Ward, 9,000
ft., 1; 1/2 mi. E and 3 mi. S Ward, 9,400 ft., 1.
#Eutamias palmeri# Merriam
Figures 17-18
General tone of upper parts grayish tawny; ocular stripe pale;
skull, rostrum, nasals, and upper incisors shorter than in _E.
umbrinus_.
Baculum: Indistinguishable from that of _E. umbrinus_. This supports the
opinion of previous students that _E. palmeri_ is a close relative of
_E. umbrinus_ which occurs immediately to the north and east.
Intergradation does not occur between these two species, for, low-lying
terrain, inhospitable to chipmunks, isolates _E. palmeri_ from its
relatives. (Verbal information from E. R. Hall.)
_Specimen examined_: One from Charleston Peak, 8,000 ft., Clear
Creek Co., Nevada.
#Eutamias bulleri# (J. A. Allen)
Figure 19
General tone of upper parts dark; dorsal dark stripes
conspicuous and black; size large; skull large.
Baculum: Shaft thick; keel high, 1/2 of length of tip; keel long, 1/2 of
length of tip; tip 40 to 48 per cent of length of shaft; angle formed by
tip and shaft 100°; base markedly widened; shaft of medium length, 3.30
mm.
For comparisons with all other species of chipmunks of western North
America, see the accounts of those species.
The large size of the keel of the baculum in this species is distinctive
among chipmunks of western North America.
_Specimens examined_: 2.
_E. bulleri bulleri_: Zacatecas: Sierra de Valparaiso, 2 (NM).
[Illustration: FIGS. 1-19. Lateral view of right side, unless otherwise
indicated, of the baculum in each of the species of chipmunks (subgenus
_Neotamias_) of western North America:
1. _Eutamias alpinus_, No. 12577 CN; from Big Cottonwood Meadow,
Tulare Co., California.
2. _E. minimus consobrinus_, No. 25439; from 13 mi. S and 2 mi. E
Robertson, 9,200 ft., Uinta Co., Wyoming.
3. _E. townsendii cooperi_, No. 53169; from Brooks Meadow, 4,300
ft., 9 mi. ENE Mt. Hood, Hood River Co., Oregon.
4. _E. sonomae sonomae_, No. 98436 BS; from Redding, Shasta Co.,
California.
5. _E. amoenus luteiventris_, No. 33811; from 7 mi. W West
Yellowstone, 7,000 ft., Fremont Co., Idaho.
6. _E. dorsalis dorsalis_, No. 213415 BS; from 3 mi. N Ft. Whipple,
5,000 ft., Yavapai Co., Arizona.
7. _E. merriami merriami_, No. 1270 LA; from Mount Pinos, Ventura
Co., California.
8 and 9. _E. quadrivittatus quadrivittatus_, No. 35648/47919 BS;
from Canon City, Fremont Co., Colorado. Figure 9 in dorsal view.
10. _E. quadrivittatus hopiensis_, No. 783 UU; from Moab, 4,500 ft.,
Grand Co., Utah.
11. _E. ruficaudus ruficaudus_, No. 33884; from 1 mi. W and 2 mi. S
Summit, 5,000 ft., Flathead Co., Montana.
12. _E. ruficaudus simulans_, No. 41478; from 13 mi. E and 5 mi. N
Coeur d'Alene, Kootenai Co., Idaho.
13. _E. cinereicollis cinereicollis_, No. 208621 BS; from Mount
Thomas, White Mountains, Apache Co., Arizona.
14. _E. quadrimaculatus_, No. 95780 BS; from Mountains near Quincy,
Plumas Co., California.
15. _E. speciosus sequoiensis_, No. 29135/41203 BS; from Mount
Whitney, Tulare Co., California.
16. _E. panamintinus panamintinus_, No. 12502 CN; from Coal Kilns,
Panamint Mountains, Inyo Co., California.
17. _E. umbrinus umbrinus_, No. 38062; from Paradise Park, 21 mi. W
and 15 mi. N Vernal, 10,050 ft., Uintah Co., Utah.
18. _E. umbrinus montanus_, No. 20105; from 1/2 mi. E and 3 mi. S
Ward, 9,400 ft., Boulder Co., Colorado. Dorsal view.
19. _E. bulleri bulleri_, No. 193142 NM; from Sierra del Valparaiso,
Zacatecas.]
DISCUSSION
In California, Johnson (1943) recognized ten species of chipmunks and
assigned these to the five main groups of species which were proposed by
Howell (1929). In characterizing each species, Johnson (_op. cit._) not
only made a careful study of skins and skulls, but also employed many
ecological data.
Study of the bacula of the Californian chipmunks supports Johnson's
(_op. cit._) conclusion that there are ten species, but suggests that
there are three (not five) groups of species in California--as well as
elsewhere within the geographic range of the subgenus _Neotamias_. The
three groups are (see figs. 1-19): 1. _minimus_-group (_E. alpinus_, _E.
minimus_, _E. townsendii_, _E. sonomae_, _E. amoenus_, _E. dorsalis_,
and _E. merriami_); 2. _quadrivittatus_-group (_E. quadrivittatus_, _E.
ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_); and 3.
_speciosus_-group (_E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_).
_Eutamias panamintinus_, according to Howell (_op. cit._:78) and Johnson
(_op. cit._:83), is a near relative of _E. amoenus_. But, the baculum in
_E. panamintinus_ more closely resembles that in _E. speciosus_ than
that in _E. amoenus_ (compare figs. 5, 15, and 16). Consequently I have
placed _E. panamintinus_ in the _speciosus_-group.
In north-central Colorado, specimens that really are _E. umbrinus_
(subspecies _montanus_) have, in the past (Howell _op. cit._:82), been
referred to _E. quadrivittatus quadrivittatus_, but the bacula of the
two species differ markedly from each other (compare figs. 8-9 with
17-18) and permit the specimens readily to be correctly identified to
species. Further, Howell (_op. cit._:95) placed _E. umbrinus_
(subspecies _umbrinus_ and _fremonti_ of current usage) in the
_quadrivittatus_-group, whereas the structure of the baculum leads me to
place _E. umbrinus_ in the _speciosus_-group.
Thus, groups of species established on the basis of only skulls and
skins, in a few instances differ from those established on a broader
basis which includes the bacula.
Johnson (_op. cit._:63) writes, "Each species [of Eutamias] has a
characteristic habitat which differs from those of other species. Where
two or more species occur together in a general locality they are
usually mutually exclusive in their choice of foraging and nesting sites
and in the time of breeding." Thus he classified the species of
Californian chipmunks not only by morphologic characteristics but by
habits and habitats as well. The characteristics of the skulls and skins
of chipmunks probably reflect the habitats in which these animals live.
The characteristics of the bacula, on the other hand, may also reflect
the habitats in which the animals live, but to a lesser degree. Because
the structures of the bacula are probably less affected by the action of
the external environment they probably indicate relationships between
groups of species of chipmunks more clearly than do characteristics of
the skulls and skins.
If the structures of the bacula indicate relationships between groups of
species of chipmunks more clearly than do the characteristics of the
skulls and skins, the close resemblance of the skulls of _E.
quadrivittatus_ and _E. umbrinus_ may be thought of as convergence. The
same can be said of _E. amoenus_ and _E. panamintinus_.
LITERATURE CITED
FRILEY, C. E., JR.
1947. Preparation and preservation of the baculum of mammals. Jour.
Mamm., 28:395-397, 1 fig., December 1.
HOWELL, A. H.
1929. Revision of the American chipmunks (genera _Tamias_ and
_Eutamias_). N. Amer. Fauna, 52:1-157, 10 pls., 9 maps.
JOHNSON, D. H.
1943. Systematic review of the chipmunks (genus Eutamias of
California). Univ. California Publ. Zool., 48:63-148, 6 pls.,
12 figs, in text, December 24.
WHITE, J. A.
1951. A practical method for mounting the bacula of small mammals.
Jour. Mamm., 32:125, February 15.
_Transmitted June 26, 1953._
24-8968
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