Description: The plains harvest mouse is a very small, delicate mammal with pale dull brown upperparts, and yellowish gray and white underparts. The outer ears and flanks are yellowish brown. The ears are large. The hind feet have six tubercules, and there are no cheek pouches. The upper incisors possess a single groove on their outer surface. Young are darker than adults. The plains harvest mouse differs from the western harvest mouse by: 1) smaller size, 2) shorter tail, 3) narrow, well-defined, black dorsal stripe, 4) narrower black tail stripe, and 5) buffy post-auricular patches. It differs from the house mouse by its 1) white underparts, 2) more hairy tail, 3) white feet and, 4) grooved incisors.
Size: Adults may attain the following dimensions: total length 105-143 mm; tail 43-63 mm; hind foot 15-17 mm; ear 12-13 mm; weight 10-12 grams.
Range and Habitat: Two subspecies occur in Kansas, Reithrodontomys montanus albescens in western Kansas, and Reithrodontomys montanus griseus in eastern Kansas. They inhabit dry uplands of the central and southern Great Plains, living in well-developed short grass and herb cover, or else in rocky, sparsely vegetated grassland where the surface rock provides cover.
Reproduction: The plains harvest mouse produces several litters annually from February to November. Two to five (usually three) young are born blind and naked after a gestation period of 21 days. In six days hair is present and in eight days the eyes open. Young are weaned in two weeks and leave the nest 10 days after weaning. Adult size is reached in five weeks, and sexual maturity in two months. Females have six nipples.
Habits: The plains harvest mouse does not hibernate, and is active at night throughout the year. They are agile climbers and may place their compact nest of dry grass in low bushes, sometimes using bird nests. Where shrubs are absent and the grass short, they may nest beneath surface rocks. Occasionally the nest is placed underground, where it is lined with soft materials. Faint trails through the scanty ground cover are maintained, but are less noticeable than those of other small field mammals.
Food: The principal food of the plains harvest mouse is seeds, but it will eat green shoots, bases of grasses, fruits, and some berries. They store food underground for use during severe winters.
Remarks: Predators of the plains harvest mouse are hawks and owls, weasels, coyotes, foxes and snakes. Longevity of this mouse in nature is less than one year.