Scientific name: Peromyscus maniculatus
Common name: Deer Mouse
(Information in this Species Page was compiled by Amy Wiester in Biology 220W, Spring
2003, at Penn State New Kensington)
The deer mouse (Peromyscus maniculatus) is one of the most numerous
organisms of the biotic community not only of our Nature Trail but also of
almost any woodland ecosystem throughout North America. It is altogether
possible, though, that even an extremely observant visitor to an ecosystem
inhabited by deer mice might never actually see one of these incredibly abundant
and extremely interesting animals.
Appearance and Habitat
The deer mouse is small. An adult’s body is only 3 or 4 inches long with a tail
of comparable length. Deer mice move about on the forest floor beneath the
concealing cover of the leaf litter, and they nest in well hidden burrows, rock
crevices, brush piles, and tree holes. Their dorsal (“back”) coloration is a
camouflaging brown, and to add a final emphasis to their cryptic habits and
habitats, they are primarily active at night. It is not surprising, then,
that they are so seldom noticed or observed.
The name “deer mouse” comes from their color patterns. They have a tawny brown
back, a white underbelly, and white legs and tails. Their colorations resemble
that of the white-tailed deer. The woodland form of the deer mouse is slightly
larger than the prairie form, but both have similar colors, hind legs that are
longer than the forelegs, large eyes, large ears, and long, thin tails. The deer
mouse is found throughout western North America (from Alaska and Canada in the
north to central Mexico in the south), and across the Great Lakes region through
Pennsylvania up into New England. They inhabit woodland ecosystems, grasslands,
alpine regions, cultivated fields, brush lands, and will even enter and nest in
buildings and homes.
The nests of the deer mice are typically lined with soft, padding and insulating
material (including moss, dried grass, rabbit fur, leaves, feathers, etc). A
nest may be inhabited by a family group of deer mice that can consist of the
parents and several of their young. Over the course of a year, a family of deer
mice may utilize several nests, typically abandoning a nest after it has become
fouled with feces and waste. Deer mice also make “larder” nests outside of the
entrances to their living nests in which gathered foodstuffs are amassed for use
when food resources are limiting.
Deer mice omnivorously take a great variety of specific foods. They gather and
eat insects (mature and immature), a wide variety of other invertebrates, seeds,
fruits, grains, fungi, flowers, and nuts. A significant percentage of the
gathered food may end up in their larder nests for winter consumption.
Life Span and Predation
Deer mice can live up to five years in captivity but probably only live about a
year in the wild. This shorter natural life span is primarily due to the very
large number of predators that take and consume deer mice. These predators
include foxes, coyotes, snakes, owls, hawks, and many other species of birds. In
the absence of these predators, deer mice populations can become explosively
large leading to serious environmental damage and degradation.
Deer mice become sexually mature at five or six weeks of age. A female deer
mouse can have up to eleven litters of one to nine young in a year. The average
gestation time for each litter is 24 days. The litter size increases until the
fifth or sixth litter and then declines. The young are tiny (1 or 2 grams) at
birth. They are weaned in four weeks and then capable of reproducing in just
another week. Litter size and frequency increase when food resources are
abundant, thus allowing this species to exploit often transiently available
resources very rapidly.
Deer mice are involved in two diseases that affect humans: Lyme disease and
hantavirus. Lyme disease is caused by a spirochete bacterium that is transferred
between mammalian hosts (including deer mice, rabbits, white-tailed deer, and
humans) by the very small deer tick, Ixodes dammini. A human with
Lyme disease often experiences a skin rash, a transient flu-like syndrome, and
may develop recurring arthritis. Hantavirus is found in the urine, feces, and
saliva of infected rodents including deer mice. Inhalation of dust containing
these viruses can lead to very serious viral infections in humans (symptoms of
hantaviral infections include headache, fever, and severe respiratory distress).
Half of those people infected with hantavirus die from the disease.