Napaeozapus insignis - The Woodland Jumping Mouse

Description:

The pelage of the woodland jumping mouse (Napaeozapus insignis) consists of a variety of different colors.  The color of its flank is a very distinct feature of this furred woodland mammal.  The fur of the flank is bright yellow-orange with black streaks running through it.  Its dorsum is dark brown fur whereas its belly is covered with snow-white fur.

The tail of the woodland jumping mouse has a diagnostic feature that can be used to distinguish it from the meadow jumping mouse (Zapus hudsonius), which it is commonly mistaken for.  The tail of both species is scaly with a dark colored ventrum and light colored dorsum.  However, the tail of the woodland jumping mouse has a white tip that the meadow jumping mouse lacks (Kurta 1995).

The total length of the woodland jumping mouse ranges from 210-250 mm whereas its weight ranges from 19 and 32 g.  Jumping mice in general have long hind feet and long tails, both of which are used in jumping behavior.  The large size of the hind feet is a good diagnostic feature that can be used to distinguish jumping mice from other types of mice.  The hind feet of the woodland jumping mouse are 28-33 mm long.  The tail of the woodland jumping mouse is at least 50% longer than its head and body.  The long tail is used for balance while bonding and is 120-155 mm long.  Ear height is 15-18 mm.

The incisors of the woodland jumping mouse are yellow-orange.  The upper incisors each have a longitudinal groove.  The dental formula is as follows: I 1/1, C 0/0, O 0/0, M 3/3 = 16.  The total number of teeth (16) is another good diagnostic feature that can be used to distinguish it from the meadow jumping mouse, which has a total of 18 teeth (Whitaker and Wrigley1972).

Wisconsin Distribution:

Woodland jumping mice are distributed throughout the temperate and boreal regions of the northern hemisphere (Bower and Cade 1966).  They can be found throughout the woodlands of the northern half of Wisconsin. Very little fossil data has been collected on the woodland jumping mouse.  It is believed that the woodland jumping mouse moved north into its present range with the retreating of the Wisconsin glaciations.  The earliest know Napaeozapus are from mid-Pleistocene deposits found in Maryland.  Remains have also been found at four late-Pleistocene sites, two of which are in the southern portion of the woodland jumping mouse’s range (Wrigley 1972).  Wisconsin is also in the southern portion its range so it may be assumed that the woodland jumping mouse inhabited Wisconsin sometime in the mid to late-Pleistocene.

Ontogeny and Reproduction:

Both male and female woodland jumping mice are not sexually active until their second season.  Mating begins shortly after females emerge from hibernation, in late April to early May.  Nests are typically grapefruit-size and are composed of dried leaves or grass.  Nests can be found in under ground burrows, hollow logs or other protected places.  Female woodland jumping mice typically produce two litters per year.  The first litter is usually born sometime in June and the second is usually born sometime in August.  Gestation ranges anywhere from 23-29 days.  Litter size is typically five young but may range from 2-7 young.

Young are born naked with loose pinkish skin.  Newborns usually weight less than a gram.  Their eyes are closed and the pinna of the ear is sealed and totally folded.  Their total length is about 35 mm, tail length is about 11 mm, and their hind foot length is 5 mm.  By day 10 pigment spot are visible beneath the skin and the ear pinna are unfolded.  By day 14 the body is covered with hair.  Total body length at this point is about 73 mm, tail length is about 25 mm, hind foot length is about 12 mm and their weight is about 4 g.  By day 19 the claws are well formed and the lower incisors protrude from the gum and by day 24 the upper incisors also protrude form the gum.  By day 26 the eyes are open, total length is about 123 mm and weight is about 8.5 g.  By day 31 the incisors are yellow and the grooves on the upper incisors are prominent.  By day 34 the young are adult-like with the exception of their size and some color variation.  Between days 63 and 80 the young molt into their adult pelage and after that they molt once each year.  Woodland jumping mice have been known to live 3-4 years (Whitaker and Wrigley 1972).

Ecology and Behavior:

Woodland jumping mice are almost always found in cool moist forests.  They inhabit spruce-fir and hemlock-hardwood forests and their range coincides well with the combined ranges of balsam fir (Abies balsamea) (Wrigley 1972).  Unlike the meadow jumping mouse, the woodland jumping mouse is almost never found in open areas.  Woodland jumping mice require heavy ground cover, usually in the form of vegetation such as ferns and mosses, and because of this are closely associated with water.  Their home range can be anywhere from 0.4-3.6 ha.  Woodland jumping mice are nocturnal and typically spend the day light hours hiding in clumps of vegetation (Whitaker and Wrigley 1972).

Woodland jumping mice exhibit an array of locomotion types.  Most of their movements are slow and done with the use of all four limbs.  They may move about freely, use burrows of other animals or use runways in their day to day movements  When alarmed they take on saltatorial locomotion (bonding with the hind limbs), and are capable of jumping distances of 1.5-3 m per bond at a height of 0.6-0.9 m (MacDonald 1984).  A mouse will bond away, stop immediately and remain motionless under think cover to avoid predation.  Woodland jumping mice are prey for a variety of carnivores including snakes, wolves, hawks, owls, weasels, and wild and domestic cats.  Because of their close association with water, woodland jumping mice can often be found swimming.  They also are capable of climbing up into shrubs but not up the truck of a tree.

Woodland jumping mice eat squatting on their hind feet and use their forelimbs to grasp food and bring it up to their mouth (Kurta 1995).  They eat a large variety of food found throughout the forests they inhabit.  Seeds (especially grass seeds), fruits and berries are very important sources of food throughout the warm season.  Most of the animal food they eat is moth larvae, ground beetles, and snout beetles.  Endogone, a subterranean fungus, makes up 35% of their diet and is considered one of their most important food sources (Whitaker and Wrigley 1972).

With the shortening of the days in October the woodland jumping mouse begins to put on anywhere from 6-10 g of fat for winter hibernation.  Hibernation typically takes place in a burrow of a bank or other raised area, where they curl up into a tight ball, lower their body temperature to just above freezing, and remain for 6-9 months (MacDonald 1984).

Literature Cited:

Brower, J.E. and T.J. Cade.  1966.  Ecology and physiology of Napaeozapus insignis (Miller) and other woodland mice. Ecology 47:46-62.

Kurta, A.  1995.  Mammals of the great lakes region.  The University of Michigan press.

MacDonald. D. 1984. The encyclopedia of mammals. Andromeda Oxford limited.

Whitaker Jr., J. O. and R. E. Wrigley. 1972. Napaeozapus insignis. Mammalian species.  Number 14, pages 1-6.

Wrigley, R. E. 1972. Systematics and biology of the woodland jumping mouse, Napaeozapus insignis. Illinois Biological Monographs 47.

Reference written by Bob Ellenbecker, Biology 378 student.  Edited by Christopher Yahnke.
Page last updated 4-29-04.