Scientific name: Napaeozapus insignis
Common name: Woodland jumping mouse
(Information for this species page was partially compiled by Sarah Allison for Biology 220W at Penn State New Kensington in Spring 2000)
(This species page is dedicated to Dr. John McNavage whose magnificent description of this species was one of the fundamental stimuli for the development of
the Virtual Nature Trail web site)
(Image by P. Myers from the Animal Diversity Web University of Michigan)
The woodland jumping mouse is one of the most distinctive but elusive small mammals found in forested habitats throughout western Pennsylvania. These mice have relatively small bodies (they weigh approximately one ounce with females being slightly larger than males), long tails (which typically account for more than half of the body's overall eight to ten inch length), small forefeet, and large, elongated hind feet. The long tails and hind feet are critical to the mouse's prodigious jumping ability generating the balance and the power needed to propel them on leaps that can exceed six to eight feet in length!
Woodland jumping mice are very brightly colored with yellow-brown backs, bright orange sides, and snow white bellies. They also have a dark stripe running down the middle of their backs. Their tails are dark brown on top and white underneath with a distinctive white tip of fluff on the ends. These bright colors may seem oddly garish for an organism that must avoid and frequently hide from its long list of predators, but they represent a reliable color and pattern match for the species typical, leaf-covered, forest floor habitat.
Habitat and Behavior
Woodland jumping mice are dominantly nocturnal but may also be active at dusk or at dawn. They are most likely to be active on rainy or overcast nights and typically keep to the underbrush for cover. Usually, these mice simply walk but if threatened will take off in a series of four to five long leaps after which they freeze in position. They are capable of remaining motionless for several hours relying on their colorations and cover for protection.
The woodland jumping mouse's habitat of choice is a cool, dark, moist forest floor with abundant vegetative ground cover. They are most common in deciduous forests (especially beech, maple, birch, and basswood) especially where the trees are inter-mixed with conifers like hemlock or white pine. They are often found on forested borders of ponds, swamps, and bogs, or in rocky, mountainous sites bordering streams. The key features of any preferred habitat
are dense cover and abundant moisture. Each mouse has a range of one to eight acres with considerable overlapping of individual ranges. In a given acre of forest there could
be anywhere from one to twenty-four woodland jumping mice in residence. The mice are quite tolerant of each other and may even use tail drumming as a warning communication with its fellow mice. They can be found occasionally in trees (they are very good climbers) and are also capable of swimming although only for short periods of time.
Burrow and Food
The woodland jumping mouse lives in a burrow. It may dig its own burrow or simply use an abandoned burrow of some other animal. The burrows are hard to detect because they are typically plugged up and camouflaged during the day.
Woodland jumping mice are omnivores. They eat grass seeds, seeds from woodland fruits, wild berries, May apple fruit, alder fruit and a variety of parts of other plants. They also eat caterpillars (including gypsy moth caterpillars) and beetles, but their primary food is the subterranean fungus Endogone which is their principle source of both nutrients and also dietary water.
Woodland jumping mice are true hibernators. Hibernation usually begins by mid to late
September and lasts for six to nine months. They begin to put on a layer of body fat about two weeks before entering their hibernative state. This fat can make up as much as one third of their total body weight.
Because they are true hibernators, woodland jumping mice do not possess cheek pouches for carrying seeds or display caching behaviors for storing food stuffs. Hibernation, though, is a stressful time for these mice. Up to seventy-five percent of the individuals that go into hibernation do not survive. This very high mortality may be due to insufficient fat reserves or because of severely cold temperatures freezing their bodies or because of spring flooding of their hibernaculae by rising water from the near-by streams or ponds.
The mice emerge from hibernation in April or May and immediately breed. Gestation is twenty-one to twenty-nine days, and a typical litter consists of four or five (possibly up to seven) young. The young are weaned after thirty-four days and are sexually mature four days after that. Usually there are two litters of mice per year: one in the early summer and the other in early fall. The average life span of a woodland jumping mouse is one or two years.
Many predators consume woodland jumping mice including skunks, weasels, minks, bobcats, owls, rattlesnakes, and domestic cats. The biggest factor in mortality, though, is the impact of failed hibernation
Because of their secretive habits and isolated habitats, the woodland jumping
mouse is not often observed by humans. Its beautiful colorations, though, and remarkable athleticism make it a valued species of our woodland ecosystems whose sighting and appreciation should be a goal for us all.