Microdipodops megacephalusdark kangaroo mouse

Geographic Range

These kangaroo mice are found in the Great Basin region of western United States, including Oregon, Utah, California, and Nevada. Nowak (1991), O'Farrell and Blaustein (1974).

Habitat

Kangaroo mice are found among bushes growing in soils covered with gravel or on sand dunes. The altitude of the habitat is around 1,190-2,455 meters. Burrows are constructed in soft ground with the entrance near a shrub. Burrows have simple, unbranched tunnels, elaborate nests, and a food storage room. A small territory is maintained near the burrow, but an individual's home ranges may overlap with those of several other individuals. Average home range for males is 6,613 square meters and 3,932 for females. O'Farrell and Blaustein (1974), Nowak (1991)

Physical Description

Total length measures 140-177 mm, head and body length is 66-77 mm, tail length 68-103 mm, and the hind foot is 23-27 mm long. The head is large in proportion to their body size due to the inflation of the tympanic bullae that extends to the upper portion of the cranium. The neck is fairly short. Upper parts are brownish to grayish black. Compared to the similar looking species, M. pallidus, M. megacephalus have basally plumbeous and white-tipped underparts, and the end of the tail is blackish. The distal half of the tail is darker than the proximal. The tail is not crested nor does it end in a tassle; however, it is thick and stores fat. The fat in the tail is used as a source of energy during dormancy.

The pelage is relatively long, silky, and lax. The hind feet are covered with stiff hairs on the sides, which increases the surface of the fine and soft feet. The undersurface of the hind feet are also well furred. The feet functions similar to a sand shoe in a desert.

Kangaroo mice utilize their forelegs more than kangaroo rats when running.

Compared to those of kangaroo rats, the molars of kangaroo mice do not constantly regrow. The base of the zygomatic arch is not enlarged as it is in kangaroo rats.

Several features, including long hind legs, relatively small forelegs, long vibrissae, and enlarged auditory bullae are probably adaptations to the jumping mode of locomotion.

O'Farrell and Blaustein (1974), Nowak (1991), Grizmek (1990).

  • Average mass
    13.4 g
    0.47 oz
    AnAge
  • Average basal metabolic rate
    0.168 W
    AnAge

Reproduction

Females are polyestrous. Pregnant individuals have been found from March to September. The majority of the young are born in May and June. Litter size ranges from 2 to 7 with an average of 3.9. A study done in west-central Nevada showed that the population consisted of 2:1 sex ratio favoring males. A successful reproduction has yet to be recorded in captivity. Maximum longevity (of an individual trapped in the wild) is five years and five months. O'Farrell and Blaustein (1974), Nowak (1991), Grizmek (1990).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    4
    AnAge

Lifespan/Longevity

Behavior

Microdipodops megacephalus are primarily bipedal, using large and powerful hind legs for locomotion. The small forelegs are scarcely used in moving. The tail, if used at all, functions as a balancing device. According to O'Farrell et al. (1974), bipedalism in kangaroo mice is probably the result of foraging behavior rather than mode of locomotion. Upright posture is also used in defending territory and in fleeing from danger. During nest defense, kangaroo mice make high pitched squeals. These kangaroo mice sleep on their backs with their forelimbs stretched over their heads and the hind limbs tucked on the belly. They are nocturnal and extremely sensitive to light. When exposed to a light, they seek shelter under the darkest spot available.

Peak activity occurs in the first two hours after sunset. Moonlight and temperature are additional factors affecting the activity of the kangaroo mice. Activity reaches its peak under partly cloudy skies, and ceases during rain. Activity is only observed from March to October, suggesting the kangaroo mice may hibernate.

Kangaroo mice are solitary animals and are aggressive toward one another. Cannibalism has been recorded when two individuals were kept together. Other laboratory studies showed that adults avoid one another or stay together for only one or two nights. Kangaroo mice can be easily kept in captivity.

O'Farrell and Blaustein (1974), Nowak (1991), Grizmek (1990).

Communication and Perception

Food Habits

These kangaroo mice are normally granivorous, although they feed on insects, particularly during summer when their activity reaches its maximum. The shift in diet may be caused by competition for food with pocket mice. Kangaroo mice store food in seed caches found in their burrows. O'Farrell and Blaustein (1974), Nowak (1991), Grizmek (1990).

Economic Importance for Humans: Positive

Used in laboratory researches for water conservation, renal physiology, and irradiation. http://netvet.wustl.edu/org/AWIC/misc/uncomsp.htm

Conservation Status

Although not endangered, their number has decreased due to destruction of habitat by modern agriculture and land development. Predators include the kit fox and snakes; however, humans are the biggest threat.

Other Comments

Their fossil records date back to the early Oligocene era in North America. There are currently two living species in the genus Microdipodops, M. megacephalus and M. pallidus. Kangaroo mice can survive for a long period of time without drinking water. They can obtain sufficient moisture from their food while it is metabolized, and from drops of dew. They have specially designed kidneys, which can efficiently concentrate urine and avoid loss of water. Some individuals have been reported to have survived without water for 7 months.

O'Farrell and Blaustein (1974), Nowak (1991), Grizmek (1990).

Contributors

Dai-Hong Kim (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

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

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.

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

Grizmek, 1990. Grizmek's Encyclopedia of Mammals. Volume V. McGraw-Hill Publishing Company.

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

O'Farrell, M., Blaustein, A. 1974. Mammalian Species. Microdipodops megacephalus. No. 46, pp. 1-3. The American Society of Mammalogists.

http://netvet.wustl.edu/org/AWIC/misc/uncomsp.htm