The Baculum In The Chipmunks Of Western North America Part 5

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).

[Ill.u.s.tration: 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 monta.n.u.s_, 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 a.s.signed 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 _monta.n.u.s_) 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 cla.s.sified 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.