Protecting and enhancing the natural values of Salt Spring Island and its surrounding waters


Deer Mouse

Deer Mouse

Deer Mouse Peromyscus maniculatus

The deer mouse usually differs from the white-footed mouse (P. leucopus) in having: soft, luxuriant fur that is gray on the upper parts of the body,  a uniformly colored back or a faint darker stripe along the middle, and 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 in total length, and weighs 21 g.

Their range is Canada to southern Mexico, except for the southeastern U.S. 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.

The deer mouse are omnivorous, eating small invertebrates such as insects, earthworms, snails, fungi, fruit, and even carrion. 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 in each location for later use. In spite of autumn fat deposition and food hoarding, winter starvation is a chief cause of mortality.

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.

Deer mice are regular food for many of Salt Spring Island’s predators, including hawks, owls, snakes, short-tailed shrews, mink and weasels.

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