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EASTERN HARVEST MOUSE
Reithrodontomys humulis (Audubon and Bachman 1841)

Order Rodentia : Family Cricetidae

DESCRIPTION. A diminutive harvest mouse like R. montanus, but upperparts deep brown or gray, heavily mixed with black, especially on the middorsal area; ears blackish all over rather than dark at the base and light at the tip; tail about as long as head and body, the dark dorsal and light ventral stripes about equal in width. Dental formula: I 1/1, C 0/0, Pm 0/0, M 3/3 × 2 = 16. Averages for external measurements: total length, 126 mm; tail, 61 mm; hind foot, 16 mm. Weight, 10–15 g.

Reithrodontomys humulis

DISTRIBUTION. Known in the eastern part of the state, west to Hunt, McLennan, and Fort Bend counties.

Distribution of Reithrodontomys humulis

SUBSPECIES. Reithrodontomys h. merriami.

HABITS. The eastern harvest mouse is found mainly in habitats dominated by grasses and other herbaceous plants characteristic of early vegetational succession, including places such as abandoned fields, weed-filled ditches, and briar thickets.
Eastern harvest mice are essentially nocturnal, although at times they may be active during the daylight hours, particularly during cold weather. During periods of cold weather, these mice huddle together in nests to reduce heat loss.

Reithrodontomys humulis constructs nests of shredded grass and plant fibers that are placed on the ground in tangled vegetation or above the ground in a clump of grass. The nest, about the size of a baseball, generally has a single entrance.

Although breeding may occur throughout the year, most births take place between late spring and late fall. Litter sizes range from one to eight (average three to four), and the gestation period is 21–22 days. At birth, the pups weigh approximately 1.2 g. The eyes do not open until 7–10 days, and weaning takes place between the second and fourth weeks. The young become sexually mature and are capable of breeding at about 11–12 weeks of age.

The food habits of R. humulis are not well known. They appear to feed almost wholly on seeds and grain but are known to eat grasshoppers and crickets while in captivity.

POPULATION STATUS. Rare. This is the rarest of the harvest mice in Texas, presumably due to its habitat requirements. Even though it may be common to an area, capture reports are rare.

CONSERVATION STATUS. The IUCN lists the eastern harvest mouse as a species of least concern, and it does not appear on the federal or state lists of concerned species. There is no indication that it faces serious conservation threats at the present time. Continued degradation and fragmentation of grassland habitats in the Blackland Prairies, Post Oak Savannah, and Pineywoods over time would pose a problem.

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From The Mammals of Texas, Seventh Edition by David J. Schmidly and Robert D. Bradley, copyright © 1994, 2004, 2016.  Courtesy of the University of Texas Press.

Natural Science Research Laboratory