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Petrogale brachyotisshort-eared rock wallaby

By Jesse Null

Geographic Range

This species ranges from the Kimbereley region of Western Australia, through Arnhem Land, and then eastward along the Gulf of Carpentaria to the eastern boundary of the Australian Shield, including Groote Eylandt (Nowak, 1999; Wilson & Reeder, 1993).

Habitat

Short-eared rock wallabies can be found in rocky areas or boulder-strewn outcrops, including low, rocky hills, cliffs, and gorges. These rocky areas are typically near forests, woodlands, or savannahs.

While other species of Petrogale have been threatened by introduced species, such as feral rabbits and feral goats, Petrogale brachyotis population sizes do not seem to have declined. This is due, in part, to the numerous island populations of northern Australia which have been unaffected by introduced species (Strahan, 1995; Taylor, 1984).

Physical Description

Petrogale brachyotis varies in total length from 830 to 1070 millimeters. Average adult size is 970 mm long.

Short-eared rock wallabies have ears that are not more than half the length of their heads, hence their name. The pelage is uniform in color dorsally and can have variable whitish margins. Pelage color ranges from light grey and almost white in western populations to dark grey and brown in eastern populations. They have an extremely long, bushy, and thickly-haired tail which is used primarily for balancing.

Short-eared rock wallabies have a well-padded hind foot, with the sole being roughly granulated. This characteristic gives these animals a secure grip on rocky surfaces, which is their primary habitat. The central hind claws of short-eared rock wallabies are short, exceeding the toe by only 2 or 3 mm. Female rock wallabies have a forward-opening pouch with four mammae (Nowak, 1999; Wilson & Reeder, 1993).

  • Range mass
    4 to 5 kg
    8.81 to 11.01 lb

Reproduction

Little reproductive information specific to short-eared rock wallabies is available. Available reproductive information is general to all rock wallaby species.

Rock wallaby females are polyestrous, with an average estrous cycle of 30 days and a gestation period of 30 days. Rock wallabies are marsupials, they give birth to altricial young that migrate from the end of the birth canal to a pouch that houses the nipples. Young can spend anywhere from 190 to 230 days in the mother's pouch suckling. Twins are possible but single births are most common.

Female rock wallabies reach sexual maturity at approximately 540 days, while males reach sexual maturity at approximately 590 days (Strahan, 1995; Taylor, 1984).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    1
    AnAge

Lifespan/Longevity

  • Average lifespan
    Status: captivity
    10.1 years
    AnAge

Behavior

As with reproduction, little specific behavioral information is available for short-eared rock wallabies. These animals are primarily nocturnal. They may, however, come out during the day to sun themselves on rocks (Strahan, 1995; Taylor, 1984).

Communication and Perception

Food Habits

Short-eared rock wallabies mainly feed on grasses. In dry seasons they can live for long periods of time without water by feeding on the succulent bark and roots of various trees within their habitat (Nowak, 1999).

Economic Importance for Humans: Positive

Early in Australian colonization most species of rock wallabies were hunted for their soft pelts. However, this type of exploitation has declined in recent years (Strahan, 1995).

Economic Importance for Humans: Negative

Short-eared rock wallabies were previously thought to be agricultural pests. It is currently understood that they pose no threat to human crops (Strahan, 1995).

Conservation Status

While many species of rock wallaby in Australia are threatened by continuous land development, Petrogale brachyotis' natural island populations on the northern coast of Australia help to preserve its population. Petrogale brachyotis is considered abundant, but is thought to be extinct in the extreme western portion of its range (Groves & Ride, 1984).

Contributors

Jesse Null (author), St. Lawrence University, Erika Barthelmess (editor), St. Lawrence University.

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

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.

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

Groves, R., W. Ride. 1984. Species at Risk: Research in Australia. Canberra: Australia Academy of Science.

Nowak, R. 1999. Walker's Mammals of the World. Baltimore: Johns Hopkins University Press.

Strahan, R. 1995. The Mammals of Australia. Singapore: Imago Productions.

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

Wilson, D., D. Reeder. 1993. Mammalian Species of the World: a Taxonomic and Geographic Reference. Washington: Smithsonian Institution Press.

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