Subspeciation in the Kangaroo Rat, Dipodomys ordii / KU. Vol 1 No 23

by Henry W. Setzer

Comparisons.—From Dipodomys ordii utahensis, D. o. columbianus differs as follows: Color lighter, dorsal and ventral stripes of tail brownish as opposed to black; ventral stripe of tail, in most specimens, incomplete to end of pencil as opposed to complete; lacrimal processes smaller; extension of premaxillae dorsad wider; interparietal generally narrower, smaller, quadrangular and truncate anteriorly, as opposed to spatulate and rounded anteriorly; braincase less vaulted; zygomatic arches bowed laterally as opposed to straight; styloid processes larger; cutting edge of upper incisors narrower.

From Dipodomys ordii fetosus, D. o. columbianus differs in: Hind foot shorter; color generally darker; skull larger; rostrum shorter and wider; nasals somewhat shorter; braincase more vaulted; auditory bullae less inflated; interparietal region wider; ventral border of foramen magnum more rounded (less indented); zygomatic arches straight as opposed to bowed laterally.

For comparisons with Dipodomys ordii inaquosus, Dipodomys ordii monoensis and Dipodomys ordii celeripes see accounts of those subspecies.

Remarks.—In most subspecies of Dipodomys ordii having large geographic ranges, there is a certain amount of variation, but D. o. columbianus remains relatively stable throughout its large range. Where extreme variation is noted in D. o. columbianus it is obviously the result of intergradation. This intergradation is noted between Dipodomys ordii monoensis and D. o. columbianus in Lyon County, Nevada, where the animals are referable to the former race cranially but to the latter on the basis of color. Animals from Kelton, Utah, are in color as Dipodomys ordii marshalli and cranially combine characters of D. o. columbianus, D. o. utahensis and D. o. marshalli. The sum total of their characters places them with D. o. marshalli. [Durrant and Setzer] (1945:29), and the present writer in this account, do not record any animals from Utah as belonging to D. o. columbianus. Nevertheless, the influence of D. o. columbianus is seen in the animals from Kelton, Utah.

Specimens examined.—Total, 588, distributed as follows:

Washington: Benton County: Blalock Island, 2 mi. SW Paterson, 2 (MVZ). Walla Walla County: 4 mi. E Burbank, 4 (MVZ); 2 mi. SSE Burbank, 27 (MVZ); Wallula, 7 (4 MVZ; 3 DRD).

Oregon: Gilliam County: Arlington, 1 (MVZ). Morrow County: 2-1/2 mi. SW Irigon, 6 (MVZ); Cecil, 1 (MVZ). Umatilla County: Umatilla, 10 (MVZ). Jefferson County: 7 mi. E Madras, 2 (DRD). Crook County: 2 mi. NE Prineville, 1 (MVZ); 7 mi. W Prineville, 8 (MVZ); 4 mi. SW Prineville, 23 (MVZ); Crooked River, at mouth of Bear Creek, 8 (MVZ). Lake County: Fort Rock, 1 (DRD); NE edge Alkali Lake, 8 (MVZ); 9 mi. S Adel, mouth 20 Mile Creek, 1 (MVZ); Guano Ranch, Guano Valley, 2 (DRD). Harney County: Malheur Lake, 9 (LACM); Narrows, 1 (DRD); 1 mi. S Narrows, 3 (MVZ); 5 mi. SW Narrows, 19 (MVZ); Smith Creek, 10 mi. SE Diamond, 1 (MVZ); Lake Alvord, 1 (MVZ); 1-1/2 mi. E Denio, 4 (MVZ). Malheur County: 3 mi. N Vale, 2 (MVZ); 8 mi. N Jordan Valley, 1 (MVZ); 1/2 mi. S Rome, 5 (MVZ); 1 mi. S Rome, 11 (MVZ).

Idaho: Payette County: Payette, 1 (DRD). Butte County: Arco, 1 (MVZ). Elmore County: Hammett, 1 (MVZ). Bingham County: 5 mi. E Shelley, 1 (MVZ); Blackfoot, 5 (MVZ); 3 mi. S Blackfoot, 6 (MVZ); Aberdeen, 1 (MVZ). Owyhee County: S bank Snake River, Homedale, 13 (MVZ); Indian Cove, 4 (MVZ); 5 mi. SE Murphy, 3 (MVZ); Castle Creek, 8 mi. S Oreana, 1 (MVZ); S Fork Owyhee River, 12 mi. N Nevada line, 1 (MVZ). Minidoka County: Acequia, 8 (MVZ); 4 mi. N Rupert, 2 (MVZ). Twin Falls County: Salmon Creek, 8 mi. W Rodgerson, 7 (MVZ). Power County: 5 mi. NW Michaud, 4 (MVZ); 4 mi. NE American Falls, 4 (MVZ); 6 mi. SW American Falls, 10 (MVZ).

California: Modoc County: Eagleville, 12 (CAS); 2 mi. E Eagleville, 7 (CAS); 2-1/2 mi. E Eagleville, 24 (CAS); 3 mi. E Eagleville, 6 (CAS); 5 mi. E Eagleville, 3 (CAS). Lassen County: 2 mi. W Red Rock P. O., 1 (MVZ); 1 mi. W Red Rock P. O., 4 (MVZ); Dransfield, 6 mi. E Ravendale, 5300 ft., 4 (CAS); 7 mi. E Ravendale, 1 (MVZ); 7 mi. N Observation Peak, 21 (MVZ); 6 mi. N Observation Peak, 7 (MVZ); Observation Peak, 31 (MVZ); Pete's Valley, 4 (MVZ); 5 mi. E Litchfield, 12 (MVZ); 6 mi. W Wendell, 3975 ft., 3 (CAS); 8 mi. SW Wendell, 5 (CAS); Honey Lake, 2 (LACM); 4-1/2 mi. WNW Stacy, 5 (MVZ); 3 mi. NW Warm Springs, 1 (MVZ). Plumas County: Beckwith, 1 (DRD); 2 mi. WNW Vinton, 2 (MVZ); Vinton, 18 (14 LACM; 4 MVZ); 1 mi. E Vinton, 7 (MVZ); near Vinton, 21 (DRD).