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Banner-tailed Kangaroo Rat
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.
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.
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.
Bannertails are highly adapted for saltatorial locomotion. Their
hindlegs and four-toed hindfeet are much longer than their forelegs.
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.
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.
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. Females typically have one
or two litters of one to three offspring a year. 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. Young are weaned at about one month of age. 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.
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. 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.
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. Stored food may be segregated by species, though
material is often mixed.
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