About Reithrodontomys megalotis (Baird, 1857)
This section provides a physical description of Reithrodontomys megalotis, the western harvest mouse, and compares it to similar species. The western harvest mouse has brownish fur, buff-colored sides, a white belly, and an indistinct white stripe running along its spine. Adult individuals reach a total length of 11 to 17 centimetres (4.3 to 6.7 inches), with a tail length between 5 and 10 centimetres (2.0 to 3.9 inches). Their height, measured from the ground to the highest point of the back, ranges from 1.5 to 2.0 centimetres. Mature western harvest mice weigh between 9 and 22 grams (0.32 to 0.78 oz), and this species shows no sexual dimorphism. Several similar species can be distinguished from Reithrodontomys megalotis by key traits: the plains harvest mouse (Reithrodontomys montanus) has a more distinct but narrower stripe along its spine; the fulvous harvest mouse (Reithrodontomys fulvescens) has a longer tail; the salt marsh harvest mouse (Reithrodontomys raviventris) has underbelly fur that ranges from pinkish cinnamon to tawny; and the house mouse (Mus musculus) has ungrooved incisors, unlike the grooved incisors of the western harvest mouse. The dental formula of Reithrodontomys megalotis is 1.0.0.3 / 1.0.0.3 = 16 total teeth. The distribution of this species spans continuously from southwest British Columbia and southeast Alberta in Canada, south through the United States to west Texas, northeast Arkansas, northwest Indiana, and southwest Wisconsin, and continues into the interior of Mexico as far south as Oaxaca.
