Zapus trinotatusPacific jumping mouse

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Geographic Range

Zapus trinotatus lives in Canada and the USA. The range of Z. trinotatus is bordered from southwestern British Columbia to western Washington and Oregon to the Cascade-Sierra Nevada mountain chain through California to Marin County, California on the northern San Francisco Bay. (Gannon 1988, Wilson and Reeder 1993)

Habitat

Zapus trinotatus inhabits alder salmonberry, riparian alder, and skunk cabbage marsh ecosystems found among coastal redwood forests. In the northern part of its range, Z. trinotatus lives in dense forests, alpine meadows, and wet-grassy areas of the Olympic Peninsula and Cascade Mountains of Washington; and in moist meadows, marshy thickets, and woodland edges with ferns and a weedy understory. In the central part of its range (Oregon), Z. trinotatus lives in riparian-deciduous woodlands, wet meadows where the ground is peaty, and brushy redwood, Douglas fir, and mixed evergreen forests. In the south it occurs in the humus-filled dark soils of the Pacific coast in redwood forests with rushes, sedges, bracken fern, swordfern, Johnsongrass, poison hemlock, and monkey flower. Zapus trinotatus populations become more dense with increasing rain.

(Ganon 1988)

Physical Description

The length of the tail is 112-155mm, the hind foot is 30-36mm, the ear is 14-16mm, and the total length is 221-242mm. The pacific jumping mouse is larger than other members of the genus. The coarse pelage is strongly tricolored. It has a distinct separation of dorsal and ventral colors. The dorsum is dark brown, the sides are dark orange-brown and occasionally flecked with black, the ventrum is mostly white or diffused with dusky brown, and the chest often has a patch of buff that extends to the venter. Its tail is sparsely haired, has guard hairs, and is dark brown above and white below. The ears are fringed with the same color as the dorsum or light brown, and the tip of the ear is spade-shaped. The color of the pelage becomes paler in autumn.

The skull is broad and deep in proportion to length, the pterygoid fossa wide, the zygomatic arch widely bowed, and the mesopterygoid fossae narrow. The mandible has a wide and inflected angle, and the coronoid process is long, slender, and divergent from the condyloid process. The upper incisor is narrow and grooved in front. M1 and M2 have an isolated (free) paracone, and the first primary fold divides the occlusal pattern of M1. The lower M1 lacks an anteromedian fold in the anteroconid.

The dental formula is 1/1 0/0 1/0 3/3.

The posterior of the Pacific jumping mouse's body is heavier than the fore part. Zapus trinotatus is pentadactyl, and the soles of its feet are naked. Its hind legs are much longer than its forelegs. It has a small head which is slightly elongated, and its eyes are small and are located midway between its nose and its ears. The ears are short, but longer than the surrounding fur. There are four pairs of mammae on Z. trinotatus: one inguinal, one abdominal, and two pectoral mammae pairs. There are no cheekpouches.

The pacific jumping mouse has specializations for locomotion. It has well-developed hind legs, lengthened distal elements of hind limbs and digits, a shortened body, a lenthened tail, a shortened neck with increased cervical flexure, posterior shift of its center of gravity, a modified vertebral column to 39 vertebra, a and lengthened pseudosacrum. These traits help Z. trinotatus jump.

(Nowak 1991, Gannon 1988)

Reproduction

Males become sexually active in May or June, and stay that way until September. Females are receptive in May and June. They give birth in July or August, with a gestation period of 18-23 days. There is one annual litter of 4-8 young. The altricial newborn is pink and hairless; its eyes are shut, its ears is folded, its head is short and stubby, and its facial vibrissae are not yet visable. This tiny newborn weighs .7-.9 grams. It is weaned after four weeks. It will become independent at around one month, and sexually mature the next year. The Pacific jumping mouse can reach a maximum age of at least four years in the wild. (Gannon 1988, Niethammer 1990)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual

Behavior

The Pacific jumping mouse is nervous and high strung, and may become aggressive when trapped, biting the hand of the trapper. Despite this, it is believed to be naturally gentle. When fighting, it produces a squeaking noise and vibrates its tail against the substrate rapidly to produce a drumming noise. Zapus trinotatus also jumps wildly from side to side when irritated. Infants produce a high-pitched squeal. When escaping predators, it can leap upward 90-180 cm, turn its head downward, arch its back, dive to the ground, and prepare to jump again. Alternately, it may remain motionless when a predator is detected, relying on its pelage as camouflage, and move to dense cover when the danger passes. The Pacific jumping mouse is nocturnal and crepuscular. When eating, it seizes food in its forepaws, sits back on haunches, and nibbles on its food.

During the summer, Z. trinotatus constructs a well-hidden, fragile, domed-shaped nest with a single entrance often on the ground. This nest is spherical, woven of grass, and approximately 100mm in diameter. In the fall, it finds a vacant burrow and prepares to hibernate. It does so by eating enough to double its weight with fat. While in torpor for the winter, its body temperature drops to two degrees Celsius, and it sleeps in a curled position with its tail wrapped around its body. It awakens in mid April, when the ambient temperature rises to negative six degrees Celsius or more.

During normal locomotion, Z. trinotatus crawls or takes short hops. It bounds by pushing off with its hind feet and landing on both fore feet together, using its tail for balance. Zapus trinotatus is capable of climbing bushes and is an excellent swimmer and diver.

Zapus trinotatus molts once annually.

The Pacific jumping mouse lives in groups of five to twenty other mice, but has little interaction with them outside of breeding. It is considered a solitary animal, but it is not antagonistic to strangers.

(Ganon 1988, Nowak 1991)

Communication and Perception

Food Habits

Zapus trinotatus eats mainly seeds, but also fruit, berries, insects, fungi, mollusks, and fish. To get at the seeds it cuts plant stems and grass, and it leaves the remains in a neat pile. The Pacific jumping mouse forages at ground level, and it does not store food. (Gannon 1988, Niethammer 1990)

Economic Importance for Humans: Negative

If numerous enough, Z. trinotatus can cause damage to meadows, though this is rare. (Ganon 1988)

Conservation Status

The IUCN catagorizes the status of Z. trinotatus as indeterminate. Its habitat is decreasing because of grazing by livestock and introduced deer. (Wilson and Reeder 1993, Nowak 1991)

Other Comments

The predators of Z. trinotatus include owls and cats.

Contributors

Josh Platnick (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

References

Anderson, S., J. K. Jones Jr. 1984. Orders and Families of Recent Mammals of the World. John Wiley and Sons.

Ganon, W. C. 1988. Mammalian Species. Number 315. The American Society of Mammologists.

Niethammer, J. 1990. Grzimek's Encyclopedia of Mammals. Volume 3: Jumping Rodents. McGraw-Hill Publishing Company.

Nowak, R. M. 1991. Walker's Mammals of the World. Johns Hopkins University Press. Baltimore and London.

Wilson, D. E., D. M. Reeder. 1993. Mammalian Species of the World: A Taxonomic and Geographic Reference. Second Edition. Smithsonian Institurion Press. Washington and London.