Geographic Variation in the Harvest Mouse,
Reithrodontomys megalotis,
On the Central Great Plains
And in Adjacent Regions
By
J. KNOX JONES, JR. AND B. MURSALOĞLU
The western harvest mouse,Reithrodontomys megalotis, inhabits most parts of the central Great Plains and adjacent regions of tall grass prairie to the eastward, shows a marked predilection for grassy habitats, is common in many areas, and is notably less variable geographically than most other cricetids found in the same region.R. megalotisoccurs (see Hall and Kelson, 1959:586, map 342) from Minnesota, southwestern Wisconsin, northwestern Illinois, Iowa and Missouri westward to, but apparently not across, the Rocky Mountains from southeastern Alberta to Colorado; it is known in Oklahoma only from the Panhandle, thence southward through the Panhandle and Trans-Pecos areas of Texas to southern México, westward across the mountains in New Mexico to the Pacific Coast, and northward to the west of the Rockies to southern British Columbia.
Hoffmeister and Warnock (1955) studied western harvest mice from Illinois, Iowa, northeastern Kansas, Minnesota and Wisconsin, concluded that one subspecific name (Reithrodontomys megalotis dycheiJ. A. Allen, 1895, with type locality at Lawrence, Douglas Co., Kansas) applied to all, and relegatedReithrodontomys megalotis pectoralisHanson, 1944 (type locality at Westpoint, Columbia Co., Wisconsin) to synonymy underdychei. Our study, based upon an examination of 1350 specimens, concerns the area west of the Missouri River from Kansas and Nebraska westward to Montana, Wyoming, Colorado and northern New Mexico. Our objectives were to study variation inR. megalotisin the region indicated and to decide what subspecific names properly apply to populations of the species that occur there.
Aside from the nameR. m. dychei, currently applied to western harvest mice from a large part of the region here under study, three other subspecific names need consideration:
"Reithrodontomys aztecus" J. A. Allen, 1893 (type locality, La Plata, San Juan Co., New Mexico), currently applied to specimens from northern New Mexico and southern Colorado (and adjacent parts of Arizona and Utah) east to southwestern Kansas and the Oklahoma Panhandle;
"Reithrodontomys megalotis caryi" A. H. Howell, 1935 (type locality, Medano Ranch, 15 mi. NE Mosca, Alamosa Co., Colorado), proposed for, and currently applied to, harvest mice from the San Luis Valley, Colorado, but possibly a synonym ofaztecusaccording to Hooper (1952:218); and
"Reithrodontomys dychei nebrascensis" J. A.