Scientific name: Peromyscus
Common name: White Footed Mouse
Information in this Species Page was compiled by
in Biology 220W, Spring
2000 and Emily Morse in Biology 220M, Spring 2002 at Penn State New Kensington.
The white footed mouse is an extremely common and locally abundant organism
(four to fifteen individuals per acre) that is found in almost any brushy or
wooded habitat from southern Canada throughout the continental United States.
The seventeen sub-species of P. leucopus differ in their specific
habitats of choice but all are adapted to a semi-arboreal life (they are
excellent climbers!) and all seem to prefer densely vegetated sites within which
they find cover and protection adjacent to open fields within which they forage
for food. Deciduous forests with adjacent brushy fields support the highest
densities of white footed mice. The white footed mouse has been described as the
“most successful mammal in Pennsylvania” because of its wide spread occurrence
and ability to flourish in so many different habitats.
Their nests are typically very well hidden and are established in a great
variety of specific locations: in old logs, tree stumps, abandoned bird’s nests,
squirrel’s nests, chipmunk burrows, woodchuck burrows, etc. They can also enter
human dwellings and make their nests in attics, chimneys or basements. Nests are
lined with gathered grasses, hair, leaves, feathers, milkweed silk, moss, and
many types of human-made materials. If the nest becomes too full of wastes, it
is abandoned and replaced with another.
Adult white footed mice are between sixteen and twenty centimeters long (up to
ten of these centimeters are the mouse’s tail). They weigh between ten and forty
three grams. They have large ears covered with tufts of hair, large brown eyes,
and a variety of body colors that range from brown to reddish (the summer
dominant color) to gray (the winter dominant color). Usually, the sides of the
mouse are a bit darker than the back and the head. They also typically have a
dark line running down the middle of their backs and white fur on their bellies,
ankles, and feet (hence, their names!).
The white footed mouse is a prodigious consumer of a wide range of types of
seeds. It can eat up to 30% of its body weight per day, and uses its excellent
sense of smell to actively locate, gather, and sequester seeds and other plant
materials. Their diet varies with location and season. They eat grasses, acorns,
beechnuts, hickory nuts, mushrooms, corn, fruit, chestnuts, jewel weed seeds
(which stain their stomachs a turquoise blue!), and pine and cherry seeds. They
also opportunistically feed on beetles, snails, grasshoppers, caterpillars (they
are a major predator of gypsy moth caterpillars!), crickets and flies. They hunt
and pounce on their prey much like a cat. They also feed on road kills and other
sources of carrion. During the fall, the white footed mouse caches and
sequesters huge quantities of collected food in a variety of locations. Quarts
of seeds and nuts have been collected from their nests. The mouse uses its
expandable cheek pouches to carry and transfer the seeds and nuts to their nests
and other cache sites.
In northern regions, breeding peaks in the spring and again in the fall. In the
southern regions, breeding is year round. A white footed mouse is sexually
mature at eight or ten weeks of age. The gestation period is between twenty-one
and twenty-seven days. Typical brood sizes are three to five young and females
have three to four litters per year. The female cares extensively for the young
and the males (at least under laboratory conditions) may also play a role in
rearing and nurturing the litter. The potential life span of the white footed
mouse is eighteen months to two years in the wild, but the actual rate of
predation on the mice is so intense that nearly the entire population of a site
is replaced every year.
The white footed mouse does not hibernate but, instead,
enters a state of deep sleep in its food-filled nest especially on the coldest
winter nights. It is able, though, to leave its nest on warmer nights to gather
food from its scattered caches.
Population Growth and Controls; Health Risk to Humans
The white footed mouse is a preferred prey species for a long list of avian,
mammalian and reptilian predators. Snakes, weasels, and owls are the principle
consumers of the mice, but almost any carnivore (including shrews, skunks,
coyotes, bobcats, foxes, hawks, house cats, humans and even wood ducks) can and
will eat them. In ecosystems lacking sufficient numbers of predators, the white
footed mouse can become an overly abundant and extremely destructive pest.
The white footed mouse can be a problem species when their
numbers grow beyond the limits and controls of its ecosystem. Overpopulation can
lead to excessive consumption of seeds and cause inhibition of plant germination
and dispersal. The efficiency of the white footed mouse in gathering seed is one
the main reasons that forest re-planting must employ the more time consuming and
expensive method of seedling plantings rather than simpler tree-seed
broadcasting methods. Invasion of stored grain products and the barns and
houses of humans also can lead to explosive growth rates and unacceptable
population levels of this mouse. The white footed mouse is also a carrier of the
bacterium that causes Lyme’s Disease (which is transferred by the very small
“deer” tick) and the Hantavirus (which is transmitted via an infected mouse’s
saliva, urine, or feces) which causes a serious respiratory illness in humans.
The benefits of the white footed mouse are also
considerable. Their consumption of insects and especially several economically
destructive species (like the spruce sawfly and the gypsy moth) help to maintain
numerous potential pests at environmentally acceptable levels. The activity of
the mice in digging nests and caches helps to loosen and aerate soil, and their
caching of seeds, which are not always then consumed, may actually represent a
major vector of seed dispersal for many plant species. The mice also serve as a
“buffer” food that acts to reduce predation pressure on other, more “desirable”
game animals, and fundamentally, the abundance of the mice and their very rapid
rates of reproduction provide a renewable food source for many of the dynamic
and interesting predator species of our North American ecosystems.