Discussion

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).

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 fromE. umbrinusandE. palmeri, in distal 2/3 (rather than 1/2) of shaft moderately compressed laterally; fromE. 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 ofE. speciosusand 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 fromE. bulleri, in shaft shorter, keel smaller, ridges on either side of tip distinct; distal 1/2 of shaft strongly compressed laterally. Does not differ fromE. palmeri.

For comparisons with all other species of chipmunks of western North America, see the accounts of those species.

Specimens ofE. umbrinus montanusfrom north-central Colorado have, in the past (Howell 1929:82), been referred toE. 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.

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 palmeriMerriam

Figures 17-18

General tone of upper parts grayish tawny; ocular stripe pale; skull, rostrum, nasals, and upper incisors shorter than inE. umbrinus.

Baculum: Indistinguishable from that ofE. umbrinus. This supports the opinion of previous students thatE. palmeriis a close relative ofE. umbrinuswhich occurs immediately to the north and east. Intergradation does not occur between these two species, for, low-lying terrain, inhospitable to chipmunks, isolatesE. palmerifrom 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).

Specimens examined: 2.

E. bulleri bulleri: Zacatecas: Sierra de Valparaiso, 2 (NM).

Figs. 1-19.Lateral view of right side, unless otherwise indicated, of the baculum in each of the species of chipmunks (subgenusNeotamias) 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.

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.

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

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 subgenusNeotamias. The three groups are (see figs. 1-19): 1.minimus-group (E. alpinus,E. minimus,E. townsendii,E. sonomae,E. amoenus,E. dorsalis, andE. merriami); 2.quadrivittatus-group (E. quadrivittatus,E. ruficaudus,E. cinereicollis, andE. quadrimaculatus); and 3.speciosus-group (E. speciosus,E. panamintinus,E. umbrinus,E. palmeri, andE. bulleri).

Eutamias panamintinus, according to Howell (op. cit.:78) and Johnson (op. cit.:83), is a near relative ofE. amoenus. But, the baculum inE. panamintinusmore closely resembles that inE. speciosusthan that inE. amoenus(compare figs. 5, 15, and 16). Consequently I have placedE. panamintinusin thespeciosus-group.

In north-central Colorado, specimens that really areE. umbrinus(subspeciesmontanus) have, in the past (Howellop. cit.:82), been referred toE. 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) placedE. umbrinus(subspeciesumbrinusandfremontiof current usage) in thequadrivittatus-group, whereas the structure of the baculum leads me to placeE. umbrinusin thespeciosus-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 habitatsin 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 ofE. quadrivittatusandE. umbrinusmay be thought of as convergence. The same can be said ofE. amoenusandE. panamintinus.

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 (generaTamiasandEutamias). 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

Transcriber's NoteThe following change has been made to the text:Page 631, added closing parenthesis to "(genus Eutamias of California)"

Page 631, added closing parenthesis to "(genus Eutamias of California)"

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