General: The deer mouse (Peromyscus maniculatus) is a highly adaptable North American species that is more widespread than any other species of mouse in this geographic range. They are often considered pests, inhabiting human dwellings, invading food and grain stores and carrying potentially fatal viruses.
Description: The deer mouse is a small, slender species, reaching a mature weight of 10g to 24g and a full-grown length of 4.5” to 8.75” (the tail comprising one-third to around one-half the total length of the body.) Physical characteristics vary geographically. For example, populations living in woodlands tend to be larger overall than prairie populations. In general, deer mice have pointed noses, long vibrissae (like whiskers,) prominent, black eyes, and large ears covered in fine fur. Deer mice have forelimbs that are shorter than their hind limbs and hind feet that are approximately .8” in length.
Deer mice have short, fine, dense fur that is gray to red-brown across their bodies, and white or off-white on their undersides. They often have white hair resembling tufts at the bases of their ears. One of the most distinguishing characteristics of the deer mouse is the two-toned tail, which is covered in fine hair, dark on top and lacking any pigment on the bottom. Compared to the tails of other species of North American Mice, the coloration on that of the deer mouse is much more sharply defined. In general, deer mice are furrier than both the White-Footed Mouse and the House Mouse1.
The deer mouse is a nocturnal species that tends to be most active at twilight. It is a predominantly terrestrial species, that uses walking, running and sometimes leaping as its main modes of transportation, although the deer mouse is also a skilled climber2.
Although the deer mouse is generally a solitary animal, basic social units do emerge during breeding seasons or cold months, when ten or more mice may huddle to conserve body heat (during extreme cold, mice may reduce their body temperatures and enter a daily torpor to conserve their energy.) These basic units often consist of mature males and females and some young of varying ages. Deer mice maintain home ranges that vary in size from 2600 square feet to over 32,000 square feet (that of males generally being larger than that of females.) Reproductive females are most territorial of their ranges and rarely overlap ranges with other females, since intruding females are known to commit infanticide. Ranges of males and females may overlap. The majority of activity occurs in close proximity to a mouse’s nest and food caches, constructed below ground, in a tree cavity, in a brush pile, stump or log, or within a human dwelling3. The nests are cup-shaped or spherical and made of vegetable matter, fur, or feathers. During the winter, activity becomes especially restricted and occurs mainly below the snow around the nest or within the nest for up to days at a time4.
Deer mice have highly developed senses of hearing, sight, smell and touch. They communicate with a variety of physical (postures, drumming,) chemical (scent marking,) tactile (grooming,) and vocal cues (with sounds including squeaks, trills, shrieks, and buzzing as well as drumming created by using the front paws possibly as a warning5.)
Deer mice can live up to eight years in captivity, but in the wild, do not often live longer than one year6.
Habitat: A highly adaptable species, the deer mouse can be found in every terrestrial habitat across all elevations, although their preference is for cool, moist, forests habitats. Inhabited zones include boreal and alpine forests, deserts, brush lands, prairies, agricultural areas, grasslands, and arid tropical areas.
Deer mice are a dietary staple of many carnivorous mammal and avian species, including snakes, owls, foxes, bobcats, and coyotes, to name a few7.
Location: Deer mice populations stretch across North America, from Alaska and Canada to Mexico. They are absent only in the southeastern United States and certain coastal sections of Mexico. This species is more widespread than any other species of mouse in North America, both geographically and ecologically8.
Diet: Deer mice are omnivorous and consume a diverse diet of insects, snails, earthworms, seeds, fruit, fungi, nuts, and plant matter. They are also known to eat carrion and at times, their own feces. Their sharp incisors are capable of breaking hard seeds and exoskeletons.
Deer mice cache food, especially in cooler climates or during cold months. Caches hold up to two cups of food each, consisting mostly of seeds, and are located in the ground or within cavities in trees. Despite this hoarding, starvation is a major cause of death for deer mice during winter months9.
Reproduction: Deer mice are polygamous and may breed throughout the year, although the majority of breeding takes place during warm months when there is ample food. During favorable breeding months, deer mice breed, on average, every three to four weeks, based on female estrous cycles of approximately five days.
Breeding pairs may inhabit the same nest, but females often drive males away in order to raise the young along. Typically, males offer no post-natal care. Females have a gestation period of 22 to 25.5 days. Females can experience a post-partum estrus and become pregnant shortly after one gestation period ends. The gestation period for a lactating female tends to be longer, lasting from 24 to 30.5 days. Litter size may range from one to eleven young, but contain, on average, five young. Females’ first five to six litters tend to increase in size consecutively, at which point they begin to decrease in size. The young are born hairless and blind, weighing 1.5g. Juvenile development is rapid. Hair begins to grow by the second day, the ear canals open by the tenth day, and the eyes open by the fifteenth day of life. The young cling to the mother’s nipples as she travels or are held in her mouth (one at a time.) The young are weaned in 25 to 35 days, at which point they may leave the nest and live independently. If the mother becomes pregnant with a second litter, she will eject the first litter from the nest10 (or in some instances, will leave the nest to be used by her mate with the older litter and find a new nest for the second litter11.)
Deer mice reach sexual maturity within 35 to 50 days, and females’ first estrus occurs by 49 days old12.
Notes of Interest: Deer mice are known carriers of a strain of Hantavirus, Sin Nombre virus. Humans who contract this virus develop Hantavirus pulmonary syndrome, a disease that is usually fatal13.
Deer mice that were marked and released by biologists were observed traveling 2 miles over the course of two days to return to their nest14.