The two species of Peromyscus inhabiting the Adirondacks are similar in appearance, and are not always distinguishable from external characters. The deer mouse usually differs from the white-footed mouse (P. leucopus) in having: (1) soft, luxuriant fur that is gray on the upper parts of the body, (2) a uniformly colored back or a faint darker stripe along the middle, and (3) a tail that is dark above and white below (bicolored) and is as long of longer than the combined lengths of the head and body, with a tuft of white hairs at the tip. The lower parts of the body and feet of both species are white, and both have prominent, scantily-furred, thin ears, coarse whiskers, and black, bulging eyes. An average sized deer mouse is 184 mm (7.2 in) in total length, and weighs 21 g (0.7 oz).
Range and Habitat
The range is transcontinental, and from Alaska to southern Mexico, except for the southeastern U.S. In the Adirondacks the deer mouse is wide spread, occurring in all terrestrial habitats at all elevations. Mixed and mature deciduous forest with sparse ground cover harbor the largest populations. Deer mice construct spherical or cup-shaped nests of shredded plant fibers, fur, and feathers under logs, stumps, rocks in the abandoned dens of other mammals, but prefers natural cavities of tress. This species is the most abundant small rodent of the region, and in autumn, often enters human dwellings.
Food and Feeding Behavior
The omnivorous deer mouse uses its sharp incisors to gnaw through the hard coats and seeds and the chitinous exoskeleton of beetles. Small invertebrates such as insects, earthworms, and snails form an important part of the summer diet.
Fungi, fruit, and even carrion are other foods. Deer mice cache food, especially seeds, in holes in the ground, in tree cavities, and even in bird nests, storing up to 0.6 L (1 pt) in each location for later use. In spite of autumn fat deposition and food hoarding, winter starvation is a chief cause of mortality.
Activity and Movement
The deer mouse is nocturnal, and is most active at twilight. Winter activity takes place mainly under snow rather than on its surface, and sever cold may limit travel to the vicinity of the nest, or restrict activity to the nest for a few days. This semi-arboreal species climbs well, can swim, and may forage in shallow water. The usual means of locomotion is walking or running, but when pursued, deer mice leap. Individuals that biologists have marked and then displaced have returned to their nests, on traveling 3.2 km (2 mi) in two days.
The breeding season is from late March through October, and each female produces 2-4 litters. After a gestation period of 21-37 days, a female gives birth to 3-11 (average 5 or 6) young. The newborn are naked, pink, blind, and each weighs about 1.8 g (0.06 oz). Their eyes open at 14 days, and they disperse up to 183 m (600 ft) to establish their own home ranges soon after being weaned at 21-28 days. Young deer mice become sexually mature at 35-60 days, and females may produces litters by the end of their first summer. Mortality of young is high, and even adults seldom live more that 1-21/2 years, although the potential life span is 8 years.
All predators of small mammals take deer mice. Some of these are hawks, owls, snakes, short-tailed shrews, foxes, minks, weasels, bobcats and coyotes.
- Social System - During the reproductive season, monogamous pairs may live in the same nest or the female may drive her mate away, caring for the young unaided. In some instances, the male remains with older young while the female moves to a new nest to give birth to the next litter. Although normally solitary except for the breeding season, as many as 15 individuals may share one nest during severe cold spells. Adults are sedentary and occupy small home ranges which average 0.5 ha (1.25 acre) for males and 0.3 ha (0.75 acre) for females. Home ranges of opposite sex may overlap, but not those of the same sex.
- Communication - Deer mice communicate with visual (posturing), tactile (mutual grooming), chemical and vocal signals. Vocalizations include shrieks, squeaks, trills, and sharp buzzing. A deer mouse that is disturbed may stamp its front feet rapidly, and vibrate the tail to produce a drumming noise.
Choate, J. R. 1973. Identification and recent distribution of white-footed mice (Peromyscus) in New England. Journal of Mammalogy, 54:41-49.
Klein, H.G. 1960. Ecological relationships of Peromyscus leucopus noveboracensis and P. maniculatus gracilis in central New York. Ecological Monographs, 30:387-407.
Parren, S.G. 1981. Habitat selection by small mammals in a northern hardwood forest. Unpubl. M.S. Thesis, Univ. of Vermont. Burlington. 77p.
Wolf, J.O. and D.S. Durr. 1986. Winter nesting behaviors of Peromyscus leucopus and Peromyscus maniculatus. Journal of Mammalogy, 67:409-412.