Comments on the Taxonomy and Geographic Distribution of Some North American Rodents

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Comments on the Taxonomy and Geographic Distribution of Some North American Rodents

E. RAYMOND HALL and KEITH R. KELSON

University of Kansas Publications Museum of Natural History

Volume 5, No. 26, pp. 343-371 December 15, 1952

UNIVERSITY OF KANSAS LAWRENCE 1952

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Edward H. Taylor, Robert W. Wilson

Volume 5, No. 26, pp. 343-371 December 15, 1952

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY FERD VOILAND. JR., STATE PRINTER TOPEKA, KANSAS 1952

Comments on the Taxonomy and Geographic Distribution of Some North American Rodents

E. RAYMOND HALL and KEITH R. KELSON

In preparing maps showing the geographic distribution of North American mammals we have found in the literature conflicting statements concerning the subspecific identity of several rodents. Wherever possible, we have examined the pertinent specimens. Results of our examination are given below.

Our studies have been aided by a contract (NR 161-791) between the Office of Naval Research, Department of the Navy, and the University of Kansas. Also, a grant from the Kansas University Endowment Association has permitted field work that yielded some of the specimens used for comparison. Grateful acknowledgment is made to the persons in charge of the several collections of mammals that we have consulted in order to satisfy ourselves concerning the subspecific status of specimens from many localities.

~Marmota flaviventer luteola~ A. H. Howell

A. H. Howell (N. Amer. Fauna, 37:50, April 7, 1915) referred specimens from Bridgers Pass, Wyoming, to Marmota flaviventer dacota, on the basis of paler underparts because, according to the data of Howell (op. cit.), M. f. dacota and M. f. luteola, the contiguous subspecies, do not differ significantly in other ways. Casual comparison reveals to us no additional differences between the two. We have examined the three specimens available to Howell from Bridgers Pass (Nos. 18733/25527, 18734/25528, and 18735/25529 U. S. Biol. Surv. Coll.) and find the tone of the underparts to be darker (more nearly russet) than in typical luteola. The tone, however, varies considerably, both individually and geographically, in luteola and it is possible to match almost exactly the ventral coloration of the specimens from Bridgers Pass with that of specimens from within the geographic range of luteola; Nos. 160509, from Bear Creek, 8 miles west of Eagle Peak, Wyoming, 18875 and 18731/25535, from the Laramie Mts., Wyoming, and No. 203744 from Sulphur Springs, Grand County, Colorado, all in the United States Biological Surveys Collection, are examples to the point. Being influenced by the geography of the region, we therefore consider the three specimens from Bridgers Pass best referred to the subspecies Marmota flaviventer luteola.

~Spermophilus variegatus grammurus~ (Say)

A. H. Howell (N. Amer. Fauna, 56:147, May 18, 1938) accorded Citellus [= Spermophilus] variegatus utah Merriam a geographic range that included the Kaibab Plateau of Arizona. Durrant (Univ. Kansas Publ. Mus. Nat. Hist., 6:119, August 10, 1952) assigned to S. v. grammurus a geographic range that included southern Utah from the eastern to the western border but in doing this did not mention the rock squirrel of the Kaibab Plateau of Arizona that also might be expected to be referable to S. v. grammurus. Howell (loc. cit.) had two specimens from the Kaibab Plateau. Of these we have examined the one from Big Spring (161566 BS) and find that it lacks the darker (more tawny) head and posterior back of C. v. utah and agrees with C. v. grammurus. On this basis we refer the rock squirrel of the Kaibab Plateau to the subspecies Spermophilus variegatus grammurus (Say).

~Tamias amoenus caurinus~ Merriam

This subspecies was named from the Olympic Peninsula of Washington. A. H. Howell, in his "Revision of the American chipmunks" (N. Amer. Fauna, 52:77, and fig. 5, 1929) regarded the geographic range of Eutamias [= Tamias] amoenus caurinus as the mountains of the Olympic Peninsula and most of Mt. Rainier. The geographic range of the amoenus chipmunk on Mt. Rainier almost certainly is continuous with that of T. a. ludibundus in the Cascade Mountains of which Mt. Rainier is a westward-projecting arm. There is no contact between the chipmunks of Mt. Rainier and those of the Olympic Peninsula; those on the Peninsula are geographically isolated from all others of the species and are separated from those on Mt. Rainier by approximately eighty miles of low-lying country, which is uninhabited by chipmunks of the species Tamias amoenus. Therefore, Howell's (loc. cit.) assignment of most of the chipmunks on Mt. Rainier to caurinus is open to question and Dalquest, in the "Mammals of Washington" (Univ. Kansas Publ. Mus. Nat. Hist., vol. 2, 1948) evidently thought that Howell had incorrectly identified them. On page 256 Dalquest (op. cit.) defined the geographic range of T. a. caurinus as restricted to the Olympic Peninsula and showed (fig. 81) Mt. Rainier to be in the geographic range of T. a. ludibundus. We would accept Dalquest's (op. cit.) arrangement without question and also would follow it because it is the more recent one were it not for the fact that Dalquest gives no reason for his changes. To allow us to decide the matter we have compared the pertinent materials ourselves. Catalogue numbers below are of the United States National Museum, Biological Surveys Collection, and each specimen mentioned by catalogue number is an adult female which shows much wear on the fourth upper premolar.

Of T. a. caurinus, Nos. 241902 and 241903 are from 2 mi. SW of Mount Angeles; No. 241911 is from "near" head of Dosewallips River, 6000 ft., and No. 241915 is from Canyon Creek, 3 mi. S Soleduc River, 3550 ft. Of T. a. ludibundus, Nos. 234776 and 235018 are from Barron, 5000 ft., and No. 230685 is from Suiattle River, 6500 ft. Of specimens in question, from Mount Rainier, No. 90635 is from 6500 ft., west slope; No. 232729 is from 4900 ft., Reflection Lakes, and No. 233114 is from 5300 ft., Indian Henrys.

In comparison with T. a. ludibundus, T. a. caurinus is grayer on most, or all, parts of the pelage, has less ochraceous on the sides, and the dark stripes on the sides of the head are narrower and less reddish (more grayish). The skull of caurinus is larger in certain measurements, as shown below:

======================================================================= Catalogue Occipitonasal Zygomatic Cranial Length of Greatest width number length breadth breadth nasals across upper molars ----------------------------------------------------------------------- T. a. ludibundus

234776 34.0 19.3 15.6 10.2 ... 235018 34.1 .... .... 10.4 8.0 230685 33.5 18.8 15.5 10.4 7.9

Mt. Rainier

90635 34.5 19.2 16.3 10.8 8.3 232729 .... 18.5 15.3 .... 8.2 233114 34.2 18.6 15.7 10.8 8.0

T. a. caurinus

Part 2

241911 34.5 19.7 16.2 11.3 8.3 241915 34.2 .... .... 10.3 8.3 241902 35.2 .... 16.8 11.1 8.1 241903 34.7 .... 16.0 10.8 8.4 -----------------------------------------------------------------------

Howell (op. cit.:75) referred three specimens from Glacier Basin, on the northeastern part of Mount Rainier, to T. a. ludibundus as he did also one specimen (loc. cit.) from Reflection Lakes, on the southern flank of the mountain. Our comparisons indicate the correctness of Howell's identification of the specimens from Glacier Basin; they more closely resemble ludibundus than caurinus. The specimen from Reflection Lakes, however, is only one of five or six from the same place; the others were lumped by him among the 49 that he recorded from Mount Rainier under the name caurinus. The series from Reflection Lakes, so far as we can detect, is not unusually variable and the differences that are apparent are within the normal range of variation ascribable to season, age, and individualism. Also, the series from Reflection Lakes, to us, is not appreciably different from the other series, representing the following places on Mount Rainier: Indian Henrys, 5300 ft.; W slope Mt. Rainier, 6600 ft.; St. Andrews Park, 5500 ft.; Spray Park, 5500 ft.; Paradise Park; Muddy Fork of Cowlitz River; Sunset Park, 5000 ft.; ridge between St. Andrews Park and South Puyallup River, 6000 ft.; and Owyhigh Lakes, 5350 ft.

Collectively, or individually, where there are as many as six specimens from a place, the material from Mt. Rainier (Glacier Basin excepted) is intermediate in color between T. a. ludibundus and T. a. caurinus and no more closely resembles one subspecies than the other. As may be seen from the cranial measurements recorded above, specimens from Mt. Rainier, although intermediate between the two subspecies just mentioned, resemble ludibundus in lesser zygomatic breadth and lesser cranial breadth (and, it may be added, in lesser dorsolateral inflation of the braincase), but resemble caurinus in longer skull (occipitonasal length), longer nasals and greater breadth across the rows of upper molariform teeth.

In summary: The animals from Mount Rainier, in features of taxonomic import, are almost exactly intermediate between T. a. caurinus and T. a. ludibundus. Being influenced by considerations of geographic adjacency, we refer the animals on Mount Rainier to Tamias amoenus ludibundus (Hollister).

Dalquest's (op. cit.: 85) explanation of the probable origin of Tamias amoenus caurinus is pertinent here. He writes: "The chipmunks of the Olympic Mountains [caurinus] probably reached their present range from the Cascades. Their probable path of emigration was westward from Mt. Rainier, along the glacial outwash train of Nisqualli Glacier, to the moraine and outwash apron of the Vashon Glacier and thence to the Olympics. So similar are the chipmunks of Mt. Rainier and the Olympic Mountains that Howell (1929) included Mt. Rainier in the range of caurinus."

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