Aepyprymnus rufescensrufous bettong

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Geographic Range

Aepyprymnus rufescens is the most widely distributed potoroid of the Australian region, ranging from northeastern Queensland to northeastern New South Wales. A colony can also be found on the border between New South Wales and Victoria, and occasionally along the northern Australian coast (Nowak, 1997; Ride, 1970).

Habitat

Aepyprymnus rufescens live predominately in open, temperate conditions from sea level to plateau tops. They thrive in grassy woodlands, coastal eucalypt forests, wet sclerophyll, and in low dry open woodlands with grassy understorey (Strahan, 1995). All A. rufescens build conical-shaped nests that have one entrance. Nests can be found in the hollows of fallen trees, under bushes, in grass clumps, or more rarely in open ground. Aepyprymnus rufescens use materials such as grass, hay, straw, dry ferns, and fibrous vegetation to build their nests. They pick this material up with their forepaws and pass it down the body to the tail which places the material in the nest. Replacement grass is arranged in the nest by lifting up older building material with the nose to create space. Aepyprymnus rufescens use up to five nests at any one time, and it has been proposed that nest building may only occur in the winter. On a monthly basis new nests are added as old nests are abandoned, and abandoned nests may be rebuilt and used by a neighboring A. rufescens.

Physical Description

Aepyprymnus rufescens is the largest living secies of rat kangaroo. Adult males weigh between 2.27kg and 3.0kg; adult females weigh between 1.36kg and 3.6kg. Body length ranges from

37.5cm to 52.0cm; tail length from 35 to 40cm; total length from 72.5cm to 90.0cm; and height approximately 35.0cm.

The name "rufescens" refers to the animal's reddish-brown coat color. This pelage is often described as grizzled, containing stiff, sliver-white hairs. Its hair-covered snout and the black hair on the back of its ears further distinguish this species. Aepyprymnus rufescens has a very faint whitish hip stripe, and its underside is noticeably lighter than the dorsal side (Troughton, 1962). The curved foreclaws of this species are well adapted for the scratching and excavating that aid in its food gathering. The hindfoot of A. rufescens lacks the first toe, and the third digit is proportionately longer than the rest (Strahan, 1995). The tail is semi-prehensile, thick, and evenly haired.

The skull of A. rufescens is short and broad compared to other potoroids. The frontal bone articulates with the squamosal region of the temporal bone, and the angular process forms a prominent shelf. Palatine fenestration varies within the species, however fenestrae are remarkably smaller or absent in the A. rufescens as compared to other potoroids. Aepyprymnus rufescens has a dental formula 3/1, 1/0, 1/1, 4/4. The first upper incisors are long, sharp, and blade-like. The second and third upper incisors are smaller and laterally displaced (Triggs, 1996). Characteristic of Diprotodontia, the first lower incisors project forward from the dentary. Diastemae are present but reduced, and canines appear in the upper jaw. The premolar is plagialaucoid; the molars erupt at approximately the same time and are bunodont (Ganslosser, 1990; Triggs, 1996).

  • Range mass
    1.36 to 3.6 kg
    3.00 to 7.93 lb
  • Average mass
    0.00248 kg
    0.01 lb
  • Average basal metabolic rate
    5.978 W
    AnAge

Reproduction

Aepyprymnus rufescens is polyestrous, with an estrus cycle occurring approximately every 34 days. Breeding can occur at any time during the year, but there is insufficient data from both captive and wild species to indicate a particular breeding season. Females reach sexual maturity in the 11th month, males between 12 and 13 months. Males visit female nests within their territory every night to determine if the female is sexually receptive. As the female approaches ovulation, the male waits either by the female or by her nest until she is sexually receptive. Both sexes can let out low growls during investigational behavior, which usually includes sniffing of the female by the male. A receptive female allows the male to smell her cloacal and pouch areas, and eventually permits copulation (Ganslosser, 1990).

Males will try to mount the female regardless of warning signals exhibited by unreceptive females. These females try to drive away courting males by making loud growling sounds, striking at the male with her forepaws, and dropping to her side and kicking at the male with her powerful hindlimbs (Ganslosser, 1990). In response to this attack, A. rufescens males often stamp one outstretched hind foot near the female and thresh their tails.

Once successful copulation has been achieved, the embryo has a gestational period of 22-24 days. After this time the embryo is born and affixes itself to one of the mother's four teats found in her pouch. The newborn young weighs approximately 1g at birth. Within one day of parturition, the female will mate again to produce a quiescent blastocyte. The newborn will remain in the pouch for approximately 114 days (7-8 weeks) before it is weaned. Aepyprymnus rufescens do not permanently leave the pouch until the 16th week. The juvenille animal stays with its mother for the ensuing seven weeks while it learns to feed, is groomed and shares its mothers nest. Aepyprymnus rufescens normally have one young per birth, however twins are not uncommon.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    1
    AnAge
  • Average gestation period
    23 days
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    333 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    380 days
    AnAge

Lifespan/Longevity

Behavior

Aepyprymnus rufescens is a strictly nocturnal animal, sleeping during the day in its nest and browsing for food during the night. These animals are thought to exhibit highly ritualized

behavior while communicating, however they are believed to be a fairly solitary species (Ganslosser, 1990). Aepyprymnus do not form long term ties with each other, but one male and two females within overlapping ranges may spend time as a trio. This behavior agrees with recent findings that A. rufescens forms loose polygynous associations (Strahan, 1995).

Aepyprymnus rufescens live alone in the nest; however male territories can often include the nests of several females. The male territory ranges from 75-110 hectares and the female territory ranges from 45-60 hectares (Strahan, 1995). Males are intolerant and aggressive towards one another, especially in captivity or in the presence of females. Males sometimes defend the female whom they are courting.

An Aepyprymnus can move at high speeds over short distances, bounding solely on its hindlegs and using its forelegs to aid in turning. This bipedal hop is mostly seen when the animal is traveling between feeding areas or in times of alarm. Aepyprymnus rufescens can move slowly while feeding by placing its forelegs on the ground and bringing both of its hindlegs forward simultaneously while balancing slightly on its tail (Johnson, 1983). When A. rufescens is alarmed, it emits a low hissing call and stamps its hind feet like a rabbit (Johnson, 1983). Females let out soft grunts to call pouch young that have strayed too far. Captive animals have been observed displaying "marking" behavior of introduced objects by rubbing them with their anal gland.

Communication and Perception

Food Habits

Aepyprymnus rufescens emerges shortly after sunset to begin its search for food. Aepyprymnus eats a variety of grasses, herbaceous plants, and uses its well-adapted foreclaws to dig for roots, tubers, and underground fungi. These animals can eat entire plants including seeds, flowers, and leaves, however they are not strictly herbivorous (Strahan, 1995). Aepyprymnus occasionally chews on the bones of dead animals and digs larvae out of the ground to eat. In captivity they will accept a variety of foods. Aepyprymnus rufescens can extract enough water from this diet to forego drinking altogether except in times of drought, when it excavates a hole in creek beds to attempt to reach the water level for a drink (Nowak, 1997).

Economic Importance for Humans: Positive

When taken at a young enough age, these animals can be tamed as pets.

Economic Importance for Humans: Negative

Aepyprymnus rufescens can become an irritating pest for crop farmers. During the dry season especially, they will eat plant roots, including potatoes and other tubers.

Conservation Status

Aepyprymnus rufescens currently is common (Straham, 1995), although the range has been reduced. The IUCN Red List Category is given as Low Risk (Biodiversity Group, 1996).

Other Comments

The average life span of A. rufescens is greater than five years, and captive animals have been known to live for eight years (Nowak, 1997).

Distribution over the known range is discontinuous and may be contingent upon food and shelter availability. It is believed that the former range of A. rufescens was more expansive prior to European occupation, extending even further south into northeastern Victoria. Remains of these creatures have also been found in southwestern Victoria and on Flinders Island near Tasmania (Nowak, 1997). Theories as to the cause of this species' declining range include the introduction of and subsequent predation by foxes, agricultural land clearing and cattle grazing, as well as long-term climatic fluctuation (Johnson, 1983; Nowak, 1997; Troughton, 1962).

Aepyprymnus in their natural habitat are not afraid of humans at night.

Contributors

Emily Peterson (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

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

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

1996. "Environment Australia Online - Biodiversity Group" (On-line). Accessed November 10, 1999 at http://www.biodiversity.environment.gov.au/index.htm.

Ganslosser, U. 1990. Rat-Kangaroos. Pp. 355-359 in S Parker, ed. Grizmek's Encyclopedia of Mammals Vol.1. New York: McGraw Hill Publishing.

Johnson, P. 1983. Rufous Bettong. Pp. 190-191 in R Strahan, ed. The Australian Museum Complete Book of Asutralian Mammals. London: Angus & Robertson.

Lavery, H. 1985. The Kangaroo Keepers. St. Lucia, London, New York: University of Queensland Press.

Nowak, R. 1997. "Walker's Mammals of the World 5.1" (On-line). Accessed October 13, 1999 at http://www.press.jhu.edu/books/walkers_mammals_of_the_world/prep.html.

Ride, W. 1970. A Guide to the Native Mammals of Australia. Melbourne, London: Oxford University Press.

Strahan, R. 1995. The Mammals of Australia/New rev. ed.. Chastwood, NSW: Reed Books.

Taylor, J. 1984. The Oxford Guide to Mammals of Australia. Melbourne: Oxford University Press.

Triggs, B. 1996. Tracks, Scats and Other Traces - A Field Guide to Australian Mammals. Melbourne: Oxford University Press.

Troughton, E. 1962. Furred Animals of Australia. Sydney: Angus and Robertson.