Western Harvest Mouse
This species is a slim, long-tailed mouse that has prominent, naked ears, a slender sparsely haired tail, grey above and whitish below. The harvest mouse has three pelages: juvenile, sub-adult, and adult. The juvenile pelage is rather woolly and dull grey. The adult pelage is the brightest. Moulting starts on the ventral surface and spreads over the flanks to meet on the back; then the new fur spreads fore and aft. A second point of origin is on the muzzle, the new coat spreading back to form a moult-line behind the ears. There is one annual moult each summer. It has four toes on the forefeet and five on the hind feet.
A small murid rodent, the Western Harvest Mouse is a naturally rare species associated with the grassland rodent communities of western North America. It has been extensively studied in the United States.
Across North America, the Western Harvest Mouse inhabits sagebrush steppe and agricultural areas in areas below elevations of 500 m. It forages in grasslands bordering riparian areas such as irrigation right-of-ways, coastal salt marshes, streams or lakes; and in deciduous ravines of willow, rose and trembling aspen.
The Western Harvest Mouse may have more than one nest within its home range to use as rest sites. The nest site is about the size of and shape of a baseball, consisting of grass lined with fine plant materials and can be found on the ground in clumps of grass, shrubs or logs or hanging from vegetation. There is a tiny entrance on the under side, which leads into a golfball-sized chamber, lined with the finest of plant material such as down or dandelion fluff. This species does not construct burrows, although it will use other small mammal burrows for shelter.
The young harvest mice weigh approximately 1.0 to 1.5 g at birth. They are pink, naked, and blind. Their lower incisors appear at four days; the pelage is visible at five days; the eyes open between the tenth and the twelfth day, and they begin to walk at about the same time. The young are weaned at 19 days and continue to develop rapidly
The information on the sociability of this species is rather conflicting. It has been described as 'ferocious,' 'cannibalistic,' 'not gentle,' and 'nervous,' and it has been reported that it dislikes being handled. In colonies, harvest mice appear rather sedentary and spend much of their time clustered together. On the other hand, they are remarkably compatible in mixed colonies of house mice and deer mice. They often cluster together with these other species and even form integrated social hierarchies in the mixed group.
Captive Western Harvest Mice can be induced to enter shallow torpor by exposure to temperatures below 10C. The ability to enter shallow torpor presumably is an adaptation for conserving energy during periods of stress from food deprivation, water shortage, or cool ambient temperatures. Torpor may be critical for the survival of northern populations because they are at the extreme northern limits of their range, where they may be exposed to cool temperatures. It is unknown if this species is capable of hibernation.
Diet or Growing requirements