Dipodomys spectabilisbanner-tailed kangaroo rat

Geographic Range

The banner-tailed kangaroo rat occurs in southwestern North America, from northeastern Arizona southward to Aguascalientes and San Luis Potosi, and from southern Arizona eastward to west Texas. Six of seven subspecies of this kangaroo rat occupies the same range. The seventh subspecies occurs further south (Best 1988).

Habitat

Bannertails occur in areas with well-developed grasslands and scattered shrubs (Findley et al 1975). Heavier soils are preferred because light soils may be unable to support the bannertails' complex burrow systems. Basins are avoided where basal cover of grass is low (Biota Information System of New Mexico 1997).

Physical Description

Banner-tailed kangaroo rats are the largest in their genus. Dorsally, the bannertails are a light ochraceous-buff mixed with black-tipped hairs. This buff shade is purest on the sides and palest on the cheeks. The ventral surface, forelimbs, the dorsal surface and sides of hind feet, hip stripes, supraorbital and postauricular spots, and the distal end of the tail are all pure white. An ochraceous-buff hip patch extends down the leg behind the ankle and forms a large dark spot that reaches the heel and leaves a white spot anteriorly (Best 1988).

The tail is long and the proximal half is covered with short hairs whereas the distal half is covered with long hairs. Dorsal and ventral tail stripes are gray-black to dusky and they unite to form a continuous black band around the tail subterminally. Lateral tail stripes are white and gradually narrow beyond the proximal half of the tail and disappear at the subterminal band. At the base of the tail, the white ring is nearly complete with gray to black hairs ventrally (Best 1988).

Adult bannertails molt once a year. New hair first appears on the snout and cheeks, then proceeds posteriorly to the level of the ears. Mid-dorsally, a saddle-shaped area of new hairs appears and then the molt continues anteriorly. Later, molt proceeds laterally to the shoulders and sides and posteriorly to the hind legs and rump (Best 1988).

Bannertails are highly adapted for saltatorial locomotion. Their hindlegs and four-toed hindfeet are much longer than their forelegs (Best 1988).

These kangaroo rats are extremely sexually dimorphic. Males are significantly larger in characteristics such as total length, length of tail, greatest length, width, and depth of cranium, and maxillary arch spread. Male bannertails also have the largest baculum in the genus (Best 1988).

A skin glad is located in the mid-dorsal skin over the arch of the back. This gland secretes excess oil which is usually absorbed by sand and dust. This excess oil may allow bannertails to swim better, stay drier, and float higher than other small rodents (Best 1988).

Cheek pouches are used for seed collection (Biota Information System of New Mexico 1997).

  • Average mass
    145 g
    5.11 oz
    AnAge

Reproduction

Banner-tailed kangaroo rat reproduction occurs year-round. Males are attracted to urine of estrous females and they will compete for access to her. Mating patterns include mutual circling and nonlocking copulation with a single mount. After copulation, the vagina becomes plugged with a translucent material with a consistency of stiff gelatin (Best 1988). Females typically have one or two litters of one to three offspring a year (Jones 1984). At birth, young are toothless, hairless, wrinkled, eyes and ears are closed, and they show the color pattern of adults in shades of pink. Young males grow faster in terms of mass than young females (Best 1988). Young are weaned at about one month of age (Jones 1984). Both male and female young are known to remain in their natal burrows for three to seven months. Many offspring remain in natal home ranges through reproductive maturity. This natal philopatry is common in gregarious mammals. This may provide juvenilles with access to essential resources that are not readily available outside natal home ranges. Also, mound availability is limited (Jones 1984).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    2
    AnAge
  • Average gestation period
    23 days
    AnAge

Lifespan/Longevity

  • Range lifespan
    Status: captivity
    12.7 (high) years
    AnAge

Behavior

Banner-tailed kangaroo rats do not hibernate and they are nocturnal. Maximum activity occurs at twilight. Their activity is inhibited by moonlight during the winter months but they are continuously active regardless of moonlight by about April. In the summer months and droughts, daylight and nocturnal activity increases. Time and levels of activity are most likely related to food availability (Lockard 1978). During the day or poor weather, bannertails remain in their burrows. Burrows have conspicuous dirt mounds at the openings. Each mound is occupied by an adult male or female and an animal may have more than one mound in its home range. Home ranges are small and overlap little. Bannertails are very territorial of their mounds and the thousands of seeds are stored inside of them. Rats restrict some or all of their activities to a small area near the mound to maintain exclusive possession of it and advertise their presence in it. Territories are defended by footdrumming as a long distance warning signal and by chasing as a closer-distance threat. There are no sexual differences in footdrumming in adults and juveniles and there is evidence that these kangaroo rats are able to differentiate between the footdrums of neighbors and strangers. If population densities are high, footdrumming rates may increase (Randall 1984).

Other noises bannertails are known to make are high pitched "peeee's," growls, squeaks, squeals, and chuckles (Best 1988).

Bannertails depend on flight from protection from predators such as badgers, kit foxes, coyotes, bobcats, owls, and humans (Best 1988).

Communication and Perception

Food Habits

Banner-tailed kangaroo rats are primarily granivorous, surviving on many species of grass seeds. Seeds are collected during seed production months in the spring and fall and transported to underground caches via cheek pouches (Biota Information System of New Mexico 1997). Stored food may be segregated by species, though material is often mixed (Best 1988).

Economic Importance for Humans: Positive

Bannertails are highly palatable to man (Best 1988).

Economic Importance for Humans: Negative

Banner tails carry many fleas which could be passed on to humans.

Conservation Status

Banner-tailed kangaroo rat habitats may be at risk due to land development by humans.

Other Comments

Bannertails have a number of adaptations for survival in arid environments. Water is not usually available in its pure form, so it is converted from the dry seeds that these kangaroo rats eat. Also, bannertails do not sweat or pant (Desert USA Magazine 1996). Large numbers of supraoptic nuclei cells with multiple nucleoli are correlated with the bannertails ability to conserve water. Highly concentrated urine is alkaline and there is a delay in excretion of water and salt. Air in burrows has a higher humidity content than outside air. This is necessary for water balance. Without the higher humidity, rate of evaporation from the lungs could exceed the rate of formation of metabolic water (Best 1988). At least 23 species of fungi have been isolated from several species of seeds occurring in the caches. These seeds may already have been colonized by fungi prior to their harvest by the rats. Handling of the seeds may also lead to further inoculation with spores of storage molds from the rodents' burrow (Reichman et al 1985).

Placement and management of seed caches by rodents can directly affect spore germination and mold growths. Seeds at the greatest depths are relatively dry and mold free. Caches nearest the surface are moist and mycologically very active. It has been found that kangaroo rats move seeds to different depths and humidities based on their levels of moldiness. Rats also seem to prefer slightly moldy seeds over very moldy and non-moldy seeds (Reichman et al 1985).

Contributors

Jessica E. Light (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

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Best, T.L. 1988. Dipodomys spectabilis. Mammalian Species #311. The American Society of Mammalogist.

Biota Information System of New Mexico. 1997. Http://www.fw.vt.edu/fishex/nmex_main/species/050625.htm

Desert USA Magazine. 1996. Http://www.desertusa.com/aug96/du_krat.html

Findley, J.S., Harris, A.H., Wilson, D.E., and C. Jones. 1975. Mammals of New Mexico. University of New Mexico Press.

Jones, W.T. 1984. Natal philopatry in bannertailed kangaroo rats. Behavioral Ecology and Sociobiology. 15: 151-155.

Lockard, R.B. 1978. Seasonal Change in the Activity Pattern of <I>Dipodomys spectabilis</I>. Journal of Mammalogy. 59(3): 563-568.

Reichman, O.J., Wicklow, D.T., and C. Rebar. 1985. Ecological and Mycological Characteristics of Caches in the Mounds of <I>Dipodomys spectabilis.</I> Journal of Mammalogy. 66(4): 643-651.

Randall, J.A. 1984. Territorial defense and advertisement by footdrumming in bannertail kangaroo rats (<I>Dipodomys spectabilis</I>) at high and low population densities. Behavioral Ecology and Sociobiology. 16: 11-20.