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).
Perception Channels: tactile ; chemical
Banner-tailed kangaroo rat habitats may be at risk due to land development by humans.
IUCN Red List of Threatened Species: near threatened
Banner tails carry many fleas which could be passed on to humans.
Bannertails are highly palatable to man (Best 1988).
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).
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).
Biogeographic Regions: nearctic (Native )
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).
Terrestrial Biomes: desert or dune ; savanna or grassland
Range lifespan
Status: captivity: 12.7 (high) years.
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).
Other Physical Features: endothermic ; bilateral symmetry
Average mass: 145 g.
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 birth mass: 7.75 g.
Average gestation period: 23 days.
Average number of offspring: 2.
