Peromyscus maniculatus
deer mouse

Peromyscus maniculatus is a North American species. It is distributed from the northern tree line in Alaska and Canada southward to central Mexico. It is absent from the southeastern United States and some coastal areas of Mexico within this range (Baker 1983).

Peromyscus maniculatus occupies many different ecological zones throughout its range. Deer mice can be found in alpine habitats, northern boreal forest, desert, grassland, brushland, agricultural fields, southern montane woodland, and arid upper tropical habitats. Also, P. maniculatus is found on boreal, temperate, and tropical islands. However, its most common habitats are prairies, bushy areas, and woodlands (King 1968).

Peromyscus maniculatus has a small body size, no longer than that of a house mouse. It is typically 119 to 222 mm long and weighs between 10 and 24 grams. Tail length is variable in different populations and ranges from 45 mm to 105 mm (Baker 1983). Woodland forms are typically larger and have larger tails and feet than prairie forms (LTER 1995). Peromyscus maniculatus has a round and slender body. The head has a pointed nose with large, black, beady eyes. The ears are large and have little fur covering them. The vibrissae are long and prominent. Peromyscus maniculatus has shorter forelimbs than hind limbs (Baker 1983).

Peromyscus maniculatus is grayish to reddish brown with white underparts. The fur is short, soft, and dense. The finely-haired tail is bicolored, the darker top half and the lighter bottom sharply differentiated. This differs from the other species of Peromyscus (Peromyscus leucopus), in which the separation of the two colors is less distinct. There are other characteristics that help distinguish P. maniculatus from the similar P. leucopus. Peromyscus maniculatus generally has hind feet that are 22 mm or less, while P. leucopus usually has hind feet 22 mm or more. Also, Peromyscus maniculatus is more richly colored with a brownish or tawny pelage, whereas P. leucopus tends to be more pinkish-buff or grayish, with scattered dark hairs (LTER 1995). These characteristics vary geographically, however, and in some areas the two species are extremely difficult to distinguish based on external morphology.

Like most murids, Peromyscus maniculatus has a dental formula of 1/1 0/0 0/0 3/3. Its molars are low-crowned and cuspidate. The third upper molar is less wide than the first two, while that of Peromyscus leucopus is approximately as wide as the first two (Baker 1983).

In captivity, P. maniculatus can live as long as eight years. However, in the wild, life expectancy is much shorter, usually less than a year (Baker 1983).

Peromyscus maniculatus is primarily a nocturnal species. Peromyscus maniculatus spends most of its time on the ground but it is also an adept climber. Activity centers around a nest and food cache. In terrestrial prairie subspecies, a nest is constructed just below ground level in its own burrow or one abandoned by another animal. Forest dwelling subspecies construct nests near the ground in stumps, logs, brush piles, tree cavities, reconstructed bird nests, tree bark, or even cottages or outbuildings. Nests are made of rounded masses of vegetable matter (as much as 100 mm in diameter) (Baker 1983).

A mature male, a few mature females, and several young constitute the basic social unit of the deer mouse. In the winter, groups of ten individuals or more of mixed sexes and ages may huddle together in nests to conserve heat. Also during winter, P. maniculatus may enter a daily torpor to reduce body temperature and conserve energy (Baker 1983).

Home Range

Home ranges of P. maniculatus range from 242 square meters to 3000 square meters. Home ranges of males are larger than females and show more overlap. Males use their home ranges for both access to feeding and nesting and also to reproductive females. Females use their home ranges for feeding, nesting, and rearing young.

Reproductive females are more aggressive in territory defense than males, and their territories overlap less, suggesting that they have a greater investment in territory defense than males. Intruding conspecifics will commit infanticide of young unattended by a female (Kirkland and Layne 1989).

Deer mice perceive their environment through keen senses of hearing, touch, smell, and vision. They communicate using tactile, visual, chemical, and auditory signals. They groom one another, posture, emit pheromones, mark their territories with scent, and make a variety of squeaky vocalizations. Sometimes when disturbed they drum their front paws rapidly up and down against a hard surface; this may serve as a warning signal to other deer mice.

Peromyscus maniculatus is omnivorous. It eats a wide variety of plant and animal matter depending on what is available, including insects and other invertebrates, seeds, fruits, flowers, nuts, and other plant products. Deer mice sometimes eat their own feces (coprophagy). In cooler climates, deer mice cache food in secret granaries during the autumn months (Baker 1983).

Deer mice are a staple in the diet of a wide variety of animals. Night-hunting predators, including snakes, owls, and various carnivorous mammals, are their biggest threat.

Peromyscus maniculatus helps disperse the seeds of a number of species of plants, and also the spores of mycorrhizal fungi. In addition, deer mice are a food source for a wide variety of animals at higher trophic levels.

Deer mice consume seeds of valued forest trees, sometimes preventing regrowth. In addition, P. maniculatus can be destructive by raiding stored grains and other food supplies, gathering litter, and gnawing (Baker 1983). Finally, P. maniculatus is a host for strain of hantavirus called Sin Nombre virus (also called Four Corners or Muerto Canyon virus). This virus, which can be contracted by humans from deer mice, causes an often fatal disease termed hantavirus pulmonary syndrome (Rowe et al. 1995).

Peromyscus maniculatus provides food for a number of carnivores, some of which are economically valuable fur-bearing mammals. Also, deer mice consume some insects that are considered pests (Baker 1983).

Peromyscus maniculatus is an abundant species, often among the most abundant mouse species of certain areas (LTER 1998). Densities can reach 11 mice per acre (Baker 1983). Quantity and quality of foods, availability of water, number and distribution of nest sites, architecture of living and dead vegetation, and depth and density of litter are some ecological factors proposed to affect the density of P. maniculatus. However, only the availability of food has been studied in enough detail to show it has an effect on population density (Kirkland and Layne 1989).

In Michigan, there are three distinct subspecies of deer mice. Peromyscus maniculatus maniculatus is found only on Isle Royale. Peromyscus maniculatus gracilis is found in forests of the northern Lower Peninsula and the Upper Peninsula, and Peromyscus maniculatus bairdii is found in open areas (preferably plowed or cultivated fields, early stages of grasslands, or along lake shores) of the Lower Peninsula and the southwestern Upper Peninsula. Peromyscus maniculatus gracilis and P. m. bairdii differ quite noticeably. Peromyscus maniculatus gracilis has a longer tail, ears, skull, and hind foot than P. m. bairdii. It is interesting that despite having sympatric ranges these subspecies do not interbreed. One possible explanation for this is the difference in habitat preference of the two species, limiting their contact (Baker 1983).