Dipodomys compactus

Geographic Range

Dipodomys compactus has a limited distribution in the southernmost region of Texas and on the islands in the Gulf of Mexico just off the Texas coast. The islands they inhabit run from the Padre Island region in the North, to the barrier islands of Tamaulipas Mexico in the South.

• Biogeographic Regions
• nearctic nearctic
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

The habitat of D. compactus remains relatively homogeneous throughout their range. Sandy soils that are disturbed or loose are favored. Along with sandy soils, they have a preference for open, sparsely vegetated dunes. Almost all of these animals are captured on the leeward or sheltered side of the landform they inhabited. It is also noteworthy that very few individuals have been captured in undisturbed brush covered areas.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• desert or dune desert or dune

• Other Habitat Features
• agricultural agricultural

Physical Description

Dipodomys compactus is of medium size, weighing between 44 and 60 g. Males of the species are larger than females, weighing an average og 53 g compared to the average of 45 g for females. However, males are smaller in cranial comparisons. The total length of these animals is between 203 and 266 mm, with males averaging 228.1 mm and females averaging 227.6 mm. The tail length is between 104 and 135 mm, with males and females both averaging just over 199 mm.

Pelage coloration varies slightly between individuals. The color can range from a gray phase to a reddish orange tint. The varying color is found underneath the black guard hairs on the back, and more noticeably on the sides. The hairs are short and fairly coarse. All color phases have white cheek patches.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike
• male larger

Reproduction

The only time D. compactus is not solitary is during the breeding season. Other than that, very little is known of the breeding and mating behaviors. Sexual dimorphism in this species suggests polygyny.

Very little is known of the reproductive behavior of D. compactus . Two individual cases have been observed and recorded. A pregnant female was captured on the 6th of July while carrying 2 embryos. A separate female was taken on the 23rd of August showing signs of two placental scars.

Reproduction in other species of this genus has been fairly well documented. In the genus Dipodomys , breeding can occur throughout the year, but tends to be fine tuned to food availability. Most species are polyestrous. The estrous cycle in Dipodomys ordii is short, lasting only 5-6 days. Cycle lengths for Dipodomys merriami and Dipodomys microps were recorded as 12 and 13 days, respectively. It is not know where in this range of variation D. compactus falls. Most species in the genus can produce two or three litters in a year.

Gestation lengths of between 29 and 26 days have been recorded for members of the genus. The longest gestations were recorded after a postpartum estrus. Litter sizes of 1 to 6 young have been recorded, which is consistent with the average of 2 young per litter observed in D. compactus .

The young are altricial, with birth weights of 3 to 6 g. In Dipodomys hermanni , hairs are reported to be visible at approximately 14 days of age. Weaning takes place at anywhere from 21 to 29 days, although the young may remain in their natal nest for as many as five weeks. Ability to dig small pits is seen at 40 days in D. hermanni , and by two months of age, members of this species can dig tunnels as long as 20 cm. Animals within the genus Dipodomys can become reproductively mature at 2 months of age under good conditions. Adult weight in D. hermanni was not attained until 10 to 16 weeks of age, and adult pelage not until 17 to 20 weeks.

Although it is not known with certainty how D. compactus compare to other members of the genus in reproductive parameters, it is likely that it is similar.

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

No research has been done specifically for D. compactus , but in general, Dipodomys young are raised by the mother until they are ready to set out on their own. Young are born without hair, and don't open their eyes for the first two weeks of life. Dipodomys mothers have been known to move their litters around by carrying them to avoid danger or flooding. Male parental behavior has not been reported.

• Parental Investment
• no parental involvement
• altricial altricial
• pre-fertilization
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • protecting
    • female

Lifespan/Longevity

Dipodomys have lived up to 9.8 years in captivity. However, the average life span in the wild is around 2 years. It is likely that D. compactus compares to other members of the genus.

Behavior

Little is known about the activity of D. compactus in the wild. One laboratory study showed that most activity was at night, with any daytime activity being short in duration and related to feeding or drinking. It is thought that nocturnal habits can be attributed to both an open habitat with the subsequent risk of predation, as well as increased daytime temperatures.

Locomotion in this genus is by saltation. They can move rapidly by hopping on their hind legs. A single hop may propel an animal more than two meters. Forelegs, which are useless for hopping, are only used when walking very short distances.

Members of the genus Dipodomys are known to remove oils from their fur by bathing in the dust. Sandbathing may also help to mark territories in some species.

Kangaroo rats construct elaborate burrow systems, with many chambers and long tunnels. The construction of these burrow systems may be one of the major factors influencing the apparent preference of all members of the genus for well drained, loose soils, as such soils are easier for the animals to excavate.

Dipodomys species in general are highly solitary, fiercely territorial, and will fight savagely if they encounter conspecifics. Only one adult occupies a burrow system.

Territories are apparently maintained through aggression and also by foot drumming. Drumming of the hind feet may alert intruders, and thereby avoid an aggressive altercation. Foot drumming may also serve to help males attract females. There are also reports of foot drumming as an alarm response to snakes.

• Key Behaviors
• terricolous
• fossorial fossorial
• saltatorial saltatorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary
• territorial territorial

Home Range

The home range of this species has not been reported. However, for other species in the genus, reports of home ranges just under 0.5 ha are common. It is likely that D. compactus is similar to other members of the genus.

Communication and Perception

Research on communication in D. comapctus is not extant. However, it is likely that this species is like other members of the genus. Kangaroo rats are not highly vocal, although they do make sounds. Most communication is through scent cues and foot drumming. Tactile communication occurs between mothers and their young, between mates, and between combatants in territorial aggression. Some visual signals, such as body posture, are probably also used in communication with conspecifics.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks
• vibrations vibrations

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical

Food Habits

Preferred foods consist of grasses, seeds, annual plants, and shrubs. Insects, fruits, buds, leaves, and stems also make up a part of their diet. Dipodomys have been known to amass up to 50 quarts of seeds and grains in their underground storage chambers.

Like other members of the genus, D. compactus does not need to drink water. This is clearly an adaptation to the very dry habitats it occupies. These animals make water metabolically, and obtain some from the moister foods they eat. They conserve water by making really concentrated urine.

• Primary Diet
• herbivore herbivore
  • granivore granivore

• Animal Foods
• insects

• Plant Foods
• leaves
• roots and tubers
• wood, bark, or stems
• seeds, grains, and nuts
• fruit

• Foraging Behavior
• stores or caches food stores or caches food

Predation

As with any North American rodent, common ground dwelling predators include coyotes, foxes, raccoons, and various other carnivores. Rattlesnakes, owls, and hawks also prey on this species. Footdrumming may be a warning signal used when encountering snakes.

• Anti-predator Adaptations
• aposematic aposematic

Ecosystem Roles

Gulf Coast kangaroo rats are food for a variety of animals. They also implact the plant community through herbivory and dispersal of seeds.

• Ecosystem Impact
• disperses seeds
• soil aeration soil aeration

Economic Importance for Humans: Positive

There is no evidence that this species produces a postive impact on human economies, although, as food for handsome predators, it may provide some indirect benefit to human populations.

Economic Importance for Humans: Negative

Dipodomys compactus has been known to pick seeds from newly planted fields.

• Negative Impacts
• crop pest

Conservation Status

The range of D. compactus is rather small, but the population is healthy and shows no signs of decline. This species is not protected under IUCN, ESA, or CITES as of this time.

Other Comments

Dipodomys compactus is believed to be the most primative of the extant kangaroo rats due to its tooth morphology. Also, many Dipodomys go their entire life without drinking free-standing water. They have developed a way of concentrating their urine more effectively than any other North American mammal. All of their water is metabolic or comes from foods that are ingested.

Additional Links

Encyclopedia of Life

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Ryan Wilson (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.

References

Baumgardner, G. 1991. Dipodomys compactus. Mammalian Species , 369: 1-4.

Baumgardner, G. 1999. Gulf Coast Kanagaroo Rat ( Dipodomys compactus ). Pp. 524-525 in The Smithsonian Book of North American Mammals . Washington D.C. and London: The Simthsonian Institution Press.

Davis, W., D. Schmidly. 1997. Gulf Coast Kangaroo Rat. Mammals of Texas Online Edition . Accessed 11/02/2002 at http://www.nsrl.ttu.edu/tmot1/dipocomp.htm .

Eisenburg, J., W. Franklin, C. Rice, G. Schaller. 1990. Mouse Group Rodents. Pp. 136-140 in Grzimek's Encyclopedia of Mammals , Vol. 3. New York: McGraw-Hill.

Goodwin, G. 1986. The Animal Kingdom / Mammals V.1 . New York: Greystone.

Kelt, D. 1999. Pp. 529-531 in The Smithosonian Book of North American Mammals . Washington and London: The Smithsonian Institution Press.

Kennedy, M. 1973. Activity Pattern of the South Padre Island Kangaroo Rat, Dipodomys comactus true. Southwestern Naturalist , 18/2: 242-243.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition . Baltimore and London: The Johns Hopkins University Press.

1976. Bacula of Dipodomys ordii compactus and Dipodomys elator. Journal of Mammology , 57/2: 382-387.