Spermophilus brunneus

Abstract

CONTEXT AND CONTENT. Order Rodentia, Suborder Sciurognatha, Family Sciuridae, Subfamily Sciurinae, Tribe Marmotini, Genus Spermophilus, Subgenus Spermophilus (Hoffmann et al. 1993). Davis (1939) divided the Nearctic members of subgenus Spermophilus into "large-eared" and "small-eared" species groups, with S. brunneus in the large-eared group. Currently, two subspecies of S. brunneus are recognized: S. b. .brunneus (Howell), 1928:211, see above. S. b. endemicus Yensen, 1991:596. Type locality "Sand Hollow, 1 km E (up canyon from) OX Ranch headquarters; T9N, R4W, Sec. 7, NE 1/4; 5.6 km N, 5.0 km E Payette, elev. 750 m, Payette Co., Idaho." Howell (1928) originally described S. brunneus as a subspecies of S. townsendii. In 1938, Howell described S. washingtoni and elevated S. brunneus to species status. He made it clear that he had thought S. brunneus was a subspecies of what is now S. washingtoni, not a member of the S. townsendii complex (Howell, 1938; Scheffer, 1946). The two allopatric subspecies of S. brunneus are significantly different in bacular morphology, cranial morphometries, pelage color and texture, annual cycles (Yensen, 1991), and allozyme frequencies (Gill and Yensen, 1992), suggesting that they are actually distinct species. DIAGNOSIS. Compared to congeners, Spermophilus brunneus (Fig. 1) is recognized by a combination of small size (head and body <200 mm, hind foot <40 mm); medium-sized pinnae (13-18 mm), short tail (39-65 mm); brownish dorsal coloration with light spots; rufous legs, nose, and ventral tail surface; and sharply contrasting off-white eye ring (Davis, 1939; Howell, 1938; Yensen, 1991). Compared to the similar-sized S. townsendii (sensu latu), S. brunneus has much larger pinnae (13-18 vs. 6--9 mm), browner dorsal coloration, a spotted rather than flecked dorsum, less distinct lateral line, smaller auditory bullae, and a shorter, wider rostrum. Compared to S. washingtoni, S. brunneus has larger pinnae (1318 vs. 10-13 mm), darker brown dorsal coloration, less distinct dorsal spots, less contrasting lateral line, and larger and more intensely pigmented rufous patches above the nose and on the thighs. S. brunneus is distinguished from S. columbianus by its much smaller size (total length <258 mm vs. >320 mm), lack of rufous color on the throat, and less bushy, shorter tail «65 mm vs. >80 mm). S. beldingi, S. elegans, and S. armatus are all larger (head plus body length >200 mm), more gray-colored than S. brunneus, and are unspotted (Davis, 1939; Howell, 1938; Hall, 1981; Yensen, 1991). Keys to species of Spermophilus are presented in Hall