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Dipodomys compactusGulf Coast kangaroo rat

By Ryan Wilson

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. (Baumgardner, 1991)

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. (Baumgardner, 1991)

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. (Baumgardner, 1991; Baumgardner, 1999; Davis and Schmidly, 1997)

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. (Baumgardner, 1991; Baumgardner, 1999; Davis and Schmidly, 1997)

  • Sexual Dimorphism
  • sexes alike
  • male larger
  • Range mass
    44 to 60 g
    1.55 to 2.11 oz
  • Range length
    203 to 266 mm
    7.99 to 10.47 in

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. (Goodwin, 1986)

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. (Davis and Schmidly, 1997)

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. (Nowak, 1999)

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. (Nowak, 1999)

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. (Kelt, 1999; Nowak, 1999)

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.

  • Breeding interval
    Most species of Dipodomy breed two or three times per year.
  • Breeding season
    Breeding in Dipodomys may occur throughout the year, but seems to peak in the summer.
  • Average number of offspring
    2
  • Range age at sexual or reproductive maturity (female)
    60 to 84 days
  • Range age at sexual or reproductive maturity (male)
    60 to 84 days

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. (Goodwin, 1986; Nowak, 1999)

  • Parental Investment
  • no parental involvement
  • 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. (Eisenburg, et al., 1990; Goodwin, 1986)

  • Range lifespan
    Status: captivity
    9.8 (high) years
  • Average lifespan
    Status: wild
    2 years

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. (Eisenburg, et al., 1990; Kennedy, 1973)

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. (Nowak, 1999; Nowak, 1999; Nowak, 1999)

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. (Nowak, 1999; Nowak, 1999; Nowak, 1999)

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. (Nowak, 1999)

Dipodomys species in general are highly solitary, fiercely territorial, and will fight savagely if they encounter conspecifics. Only one adult occupies a burrow system. (Nowak, 1999)

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. (Nowak, 1999)

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. (Nowak, 1999)

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. (Nowak, 1999)

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. (Davis and Schmidly, 1997; Eisenburg, et al., 1990; Goodwin, 1986)

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. (Baumgardner, 1991)

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

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. (Eisenburg, et al., 1990; Nowak, 1999)

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. (Baumgardner, 1991; Goodwin, 1986)

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. (Davis and Schmidly, 1997)

  • 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. (Baumgardner, 1991)

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. (Baumgardner, 1991; Eisenburg, et al., 1990)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

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

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

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

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.

fertilization

union of egg and spermatozoan

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

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.

nocturnal

active during the night

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

soil aeration

digs and breaks up soil so air and water can get in

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

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

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

Baumgardner, G. 1999. Gulf Coast Kanagaroo Rat (Dipodomys compactus). Pp. 524-525 in D Wilson, S Ruff, eds. 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 D Wilson, S Ruff, eds. 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.

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