Napaeozapus insignis

Geographic Range

Woodland jumping mice, Napaeozapus insignis , are found throughout northeastern North America, from central Manitoba to northern Quebec and south into the lower Appalachian Mountains (northern Georgia). In Michigan, N. insignis occurs in the Upper Peninsula and in the northern three tiers of counties in the Lower Peninsula.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Boreal habitats contain higher densities of N. insignis than non-boreal habitats. Furthermore, woodland jumping mice prefer forested areas with dense woody undergrowth. Throughout their range, woodland jumping mice are found in spruce-fir and hemlock-hardwoods. They are also found in forest edge habitats that are near water or have sufficient cover (shrubs, ferns, grasses, rocks). Woodland jumping mice occur at sea level in the St. Lawrence region and at elevations of up to 2013 m in the Appalachian highlands. Due a lack of appropriate habitat, in many areas populations of woodland jumping mice are restricted to mountain tops, relict forest patches, and cool, moist coves.

Napaeozapus insignis is found in a wide variety of habitats in Michigan. These habitats include old growth dry and wet hardwoods, second growth hardwoods, mixed conifer swamp, tamarack and black spruce bog, second-growth fir and spruce, and in grassy areas with second-growth ash cover.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• mountains mountains

• Wetlands
• swamp swamp
• bog bog

• Other Habitat Features
• riparian riparian

Physical Description

Napaeozapus insignis is a medium sized rodent that weighs between 17 and 26 g in the spring and early summer, and as much as 35 g during pregnancy or just before hibernation. Females are slightly larger than males. Total body length, from nose to end of tail vertebrae, ranges from 205 to 256 mm. They have a tricolored fur pattern with white underparts, yellowish orange sides lightly streaked with black guard hairs, and a dark dorsal stripe from nose to tail. The tops of their feet are white. Most noticeably, they have a long bicolored tail that is sparsely haired, thin, tapered, scaly, and white-tipped. Tail length ranges from 115 to 160 mm (approximately 60 % of the total body length). The number and length of tail vertebrae is increased to make this length possible. They have four pairs of mammae (1 pectoral, 2 abdominal, 1 inguinal). Adaptations of N. insignis for a saltatorial lifestyle are long hind legs with elongated ankle bones and long toe bones.

In the field, the only other rodent N. insignis could be confused with is Zapus hudsonius (meadow jumping mouse). Woodland jumping mice are rarely found in open areas, have a white-tipped tail, are larger, and are more brightly tricolored than are meadow jumping mice.

The skull of N. insignis is small, high-crowned, and similar to the skull of Z. hudsonius . Napaeozapus insignis has large, oval infraorbital foramina, small auditory bullae, a short and broad palate, and narrow zygomatic arches. They have three molariform teeth ( Z. hudsonius has four) and grooved incisors that are orange or yellow. Their molars are rooted and semi-hypsodont and they do not have premolars. Woodland jumping mice have 16 total teeth and a dental formula of 1/1, 0/0, 0/0, 3/3.

Northern populations average 12% larger in body size than southern populations. Northern and eastern populations tend to be more yellowish and southern populations are reddish orange. Northwestern populations have pale colored sides and dark backs. These distinctions in appearance and geographic differences helped Whitaker (1972) to identify five subspecies of woodland jumping mice. Napaeozapus insignis insignis is found in New Brunswick, Canada, N. i. abietorum in Ontario, and N. i. saquenayensis in Quebec. Napaeozapus insignis roanensis inhabits the Roan Mountains of North Carolina, and N. i. frutectanus is found in eastern Wisconsin and in Michigan.

Woodland jumping mice have a basal metabolic rate of 1.8 ml O2/g hr. Brower and Cade (1966) found that N. insignis has precise thermoregulation when active, deep seasonal hibernation, a high lower critical temperature, and a poor ability to tolerate high ambient temperatures. These are likely adaptations to living in the cold.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

Males come out of hibernation approximately 2 weeks before females and mating occurs immediately after both sexes emerge and again in mid to late summer (in the case of a second litter). Very few data exist about the mating system of N. insignis . In captivity, breeding females injure the ears and tails of males when pursued. However, captive woodland jumping mice are generally passive with each other (even while breeding).

Female woodland jumping mice are reproductively receptive when they emerge from hibernation in early- to mid-May. Litters are possible from May through September, peaking in June and August. The earliest record of pregnancy is May 8, however most females do not reproduce until June. There are often 2 litters in one season, although this is more common in the southern part of the range. There are usually fewer young in second litters than in first litters. Many females have their second litters in August. The latest recorded pregnancy is September 1. Wrigley (1972) found that 70% of the individuals in a population of N. insignis collected in the fall were young from that year (based on the examination of 2,529 museum specimens collected throughout their range). Woodland jumping mice that do not reproduce tend to be mice that were born in second litters the previous year. Both females and males are reproductively mature when they emerge from hibernation the year after they are born.

Compared to most other rodents, zapodids have a longer period of development. This could be due to extra time needed for growth and coordination of specialized limbs for jumping. Litters contain 1 to 7 young (average is 4.5) and the gestation period is from 23 to 29 days. Young are blind, naked, unpigmented, and weigh about 1 g at birth. By day 10, young woodland jumping mice have visible pigment spots beneath the skin all over the body. Their bodies are covered with fine hair by day 14. Young jumping mice are fully furred by 24 days and their eyes open by 26 days. By day 34, the young are weaned and they have the appearance of adults, except they are smaller and their sides are yellowish brown (adults have orange-brown sides). A molt to the adult pelage occurs between 63 and 80 days. Most adults go through their yearly molt in August.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• viviparous viviparous

Little is known about the parental care of woodland jumping mice because they are extremely difficult to observe in the wild, and most captive females kill their young shortly after they are born. Females care for the young, have smaller home ranges than males, have been observed covering the nest entrance during the day, and have been found in nests with their young. Because of their long developmental period, these mice provide a longer period of parental care than do many other small northern mice. The role of males in parental care is unknown.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Zapodids have relatively long life-spans. Brown (1970) estimated that Zapus princeps lives at least 4 years in the wild and Walter (1964) found that Sicista betulina can live 3.3 years in nature. Even though woodland jumping mice have a high turnover rate in the fall, they live longer in the wild than most other North American small mammals, up to 4 years of age. Their average lifespan is 3 years. This long lifespan is at least partly due to the ability of jumping mice to hibernate. Age is estimated by the attrition of molars and since N. insignis only uses its teeth for half of the year, determining age can be difficult.

Behavior

Napaeozapus insignis is primarily nocturnal, but may be active during the day, especially on cloudy or rainy days. Woodland jumping mice seek shelter in their own burrows (they are excellent diggers), in the burrows of other small mammals, or under shrubs. The entrance to a burrow is covered during the day. Burrows may be as long as 1.5 m. A globular nest is built in a small tunnel, in brush, or on the ground. Nests are made of grass and dead leaves, and have a diameter as large as 154 mm.

When speed is needed, a quadrupedal hop is used, but the normal mode of locomotion is a quadrupedal walk. A single hop normally covers 0.6 to 0.9 m, and can be as long as 1.8 m and as high as 0.6 m. Jumping mice use trails created by other small mammals to travel, but not nearly as regularly as do meadow voles ( Microtus pennsylvanicus ). Woodland jumping mice can climb within bushes and on vines, but are not arboreal. Finally, these mice can swim underwater and on the surface for short distances.

Woodland jumping mice hibernate for at least six months of the year. They hibernate from September or October to May in a subterranean burrow. Young do not enter hibernation until late October, about one month after adults begin hibernation. Body fat is quickly accumulated several weeks before entering hibernation. An adult that weighs 20 g in the summer may gain up to 10 g to in preparation to hibernate. While hibernating, woodland jumping mice curl up in a ball in their underground nests and enter a torpor where their normal body temperature of 37 C drops considerably. Finally, up to 35% of body weight is lost during hibernation.

In captivity, tail drumming and sporadic jumping are signs of excitability or nervousness. After approximately one month in captivity, woodland jumping mice calm considerably and can be easily handled. Woodland jumping mice do not typically display aggressive behavior towards each other or defensive behavior over food. When given the choice, they prefer to sleep in the same nest box as other woodland jumping mice.

• Key Behaviors
• terricolous
• saltatorial saltatorial
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• hibernation hibernation
• solitary solitary

Home Range

Territory sizes of small rodents are hard to determine because direct observations in the wild are difficult and it is even harder to observe defensive behavior in nature. Therefore, little is known about the territory size and territorial behavior of N. insignis . Individuals are seldom caught enough times to estimate home range size accurately, and these mice frequently move to new areas. Nevertheless, it has often been estimated that males have home ranges between 0.4 and 3.6 hectares and that ranges of females are between 0.4 and 2.6 hectares. Ranges of females and males overlap. Woodland jumping mice are highly mobile, a characteristic which helps them find food. Temporary food sources, such as ripened berries, attract relatively high numbers of woodland jumping mice. Apparent evidence of colonialism in N. insignis may actually be temporary congregations around a food source. The average population density, in favorable habitat, is 7.5 per ha. However, population density estimates range from 0.64 to 59 per ha.

Communication and Perception

Not much is known about the communication in woodland jumping mice. In captivity, individuals are very tolerant of each other and show few signs of aggression. Individuals are normally silent; however young mice are constantly squeaking and making suckling sounds shortly after being born. Adults utter a soft clucking sound while sleeping or just before hibernation.

Although not specifically reported for this species, there is undoubtedly tactile communication between mates, as well as between mother and offspring. It is also likely that, as in other small rodents, chemical signals pass between individuals helping to identify individuals, sexes, and the reproductive condition of any particular mouse.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Woodland jumping mice are omnivorous generalists. Primary food sources are fruits, seeds, fungi, and insects. Napaeozapus insignis is dependent on the fungus Endogone for food. Endogone was the most abundant food found in the stomachs of specimens from North Carolina, Tennessee, New York, and New Hampshire. Linzey (1973) found that Endogone was in the stomachs of 78% of the mice examined, adding up to 40% of the total food volume. This large percentage of consumed Endogone is not found in any other small mammal. Other plant materials found in the stomach of N. insignis were raspberries, may apples, blueberries, ferns, leaves, and nuts. Connor (1966) found that insects made up 22% of the stomach contents he examined. The insect species found were larval Lepidoptera , adult Coleoptera , and larval Diptera . Linzey (1973) found that Lepidoptera larvae made up over half of the animal foods consumed by his study animals. They do not cache food.

• Primary Diet
• omnivore omnivore

• Animal Foods
• insects
• terrestrial non-insect arthropods
• terrestrial worms

• Plant Foods
• leaves
• roots and tubers
• seeds, grains, and nuts
• fruit
• bryophytes

• Other Foods
• fungus

Predation

The tricolored pattern of the pelage of N. insignis provides camouflage against dead vegetation. Napaeozapus insignis escapes from predators with a quick jump followed by a period of remaining motionless. Their coloration, escape behavior, and relative lack of odor are probably predator avoidance mechanisms. Woodland jumping mice are mostly safe from predators during hibernation. Timber rattlesnakes ( Crotalus horridus ), broad-banded copperheads ( Agkistrodon contortrix ), screech owls ( Otus asio ), bobcats ( Lynx rufus ), minks ( Mustela vison ), striped skunks ( Mephitis mephitis ), gray wolves ( Canis lupus ), and house cats ( Felis silvestris ) are all known predators of woodland jumping mice.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Woodland jumping mice use fungi as a food source and therefore are responsible for the dispersal of mycorrhizal fungi (particularly Endogone ). Mycorrhizal fungi provide trees with essential nutrients through their roots and break down detritus; both are essential roles in an ecosystem. Napaeozapus insignis is closely associated with other small mammals such as Peromyscus leucopus (white-footed mice). Also, N. insignis populations are complementary to populations of Clethrionomys gapperi (southern red-backed voles). When one species exists, usually the other is not in that area. This may be due to aggression and not competition for resources.

External parasites of N. insignis are fleas ( Epitedia sp. and Ctenophthalmus sp. ), many species of mites, chiggers, ticks, fleas, and botflies ( Cuterebra sp. ). A tiny mite, Demacarus newyorkensis , is the most common external parasite of N. insignis , these mites can number from 1 to several 100 per mouse. Red mites ( Trombicula harperi ) are also found on woodland jumping mice. Internal parasites of N. insignis are protozoans ( Hexamita sp. ), cestodes or tapeworms ( Hymenolepis bennetti ), and nematodes or roundworms ( Citellinoides zapodis ).

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Little is known about how woodland jumping mice benefit humans. The disperal of mycorrhizal fungi by these animals benefits many species of trees, some of which may be economically important.

Economic Importance for Humans: Negative

There are no known adverse affects of woodland jumping mice on humans.

Conservation Status

Woodland jumping mice have no special status on the IUCN Red List, US Federal List, or CITES.

Other Comments

The original classification of this species was Zapus insignis (Miller) in 1891. Differences found in the dental morphology, ear ossicles, and the bacula later led to the creation of the new genera of Napaeozapus and Euzapus . Currently, N. insignis is in the family Dipodidae with jerboas, jumping mice, and birch mice. However, some systematists place woodland jumping mice in their own family, Zapodidae. Dipodidae is divided into seven subfamilies; jumping mice are in the subfamily Zapodinae .

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Erin Harrington (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

References

Baker, R. 1983. Michigan Mammals . Detroit, Michigan: Michigan State University Press.

Brower, J., T. Cade. 1966. Ecology and Physiology of Napaeozapus insignis (Miller) and Other Woodland Mice. Ecology , 47/1: 46-63.

Brown, L. 1970. Population dynamics of the western jumping mouse ( Zapus princeps ) during a four-year study. Journal of Mammalogy , 51: 651-658.

Burt, W. 1946. The Mammals of Michigan . Ann Arbor, Michigan: The University of Michigan Press.

Connor, P. 1966. The mammals of the Tug Hill Plateau, New York. New York State Museum and Science Service Bulletin , 406: 1-82.

Costello, R., A. Rosenberger. 2003. " Napaeozapus insignis , Woodland Jumping Mouse" (On-line). Smithsonian National Museum of Natural History: North American Mammals. Accessed March 29, 2004 at http://web4.si.edu/mna/image_info.cfm?species_id=207 .

Hanney, P. 1975. Rodents: Their Lives and Habits . New York, New York: Taplinger Publishing Company.

Linzey, D., C. Brecht. 2002. " Napaeozapus insignis (Miller)" (On-line). Mammalia: Mammals of Great Smoky Mountains National Park. Accessed March 29, 2004 at http://www.discoverlife.org/nh/tx/Vertebrata/Mammalia/Dipodidae/Napaeozapus/insignis/ .

Linzey, D., A. Linzey. 1973. Notes on food of small mammals from Great Smoky Mountains National Park, Tennessee-North Carolina. Journal of the Elisha Mitchell Scientific Society , 89/1: 6-14.

Walker, E. 1964. Mammals of the World . Baltimore, Maryland: Johns Hopkins Press.

Whitaker, J., R. Wrigley. 1972. Napaeozapus insignis . Mammalian Species , No. 14: 1-6.

Whitaker, J. 1963. Food, habitat, and parasites of the woodland jumping mouse in central New York. Journal of Mammalogy , 44/2: 316-321.

Wilson, D., D. Reeder. 1993. " Napaeozapus insignis " (On-line). Mammal Species of the World (MSW). Accessed March 28, 2004 at http://www.nmnh.si.edu/msw/ .

Wrigley, R. 1972. Systematics and Biology of the Woodland Jumping Mouse Napaeozapus insignis . Illinois University Biological Monographs , 47: 1-118.