Rat-kangaroos

(Potoroidae)

Class Mammalia

Order Diprotodontia

Family Potoroidae

Thumbnail description
Small- to medium-sized marsupials that generally hop like kangaroos; they have an elongated tail; females have a pouch with four teats and usually have one young

Size
6–12 in (15–30 cm); 1.3–8 lb (500–3,000 g)

Number of genera, species
4 genera; 8 species

Habitat
Forest and open woodland

Conservation status
Extinct: 2 species; Critically Endangered: 1 species; Endangered: 2 species; Vulnerable: 1 species; Lower Risk/Conservation Dependent: 1 species; Lower Risk/Near Threatened: 1 species

Distribution
Mainly coastal Australia; absent from northern coast

Evolution and systematics

Rat-kangaroos have been traditionally classified as a sub-family of their nearest relatives, the kangaroo and wallaby family (Macropodidae). However, most taxonomists now accept the separation of two groups into families with the Potoroidae being separated from the Macropodidae on the basis of their urogenital anatomy. The two groups are often associated into a single superfamily, the Macropodoidea. These families have been separate for at least 50 million years. Within the Potoroidae there is one group: the Potoroinae, which contains the extant genera of Potorous, Bettongia, and Aepyprymnus. Within the Potoroinae, Bettongia and Aepyprymnus are more closely related to each other than to Potorous.

Physical characteristics

These animals are all smaller than a medium-sized cat. The upper fur is variously gray-brown with the belly usually much lighter. The ears are short and rounded. The face is short though the nasal region is somewhat elongated. The fore-limbs are considerably shorter than the hind limbs, which are

elongated in a similar manner to that of the larger kangaroos. The tail is usually furred, and in the brush-tailed bettong (B. penicillata), there is a crest on the distal dorsal surface. In P. tridactlus and B. gaimardi, the tail tip is white; the significance of this is not known. Some bettongs have a prehensile tail that is used to transport nest material (leaves and grass) for nest building. There are three pairs of upper incisors but only one pair of lower, and young potoroids have two premolars, though near maturity these are replaced by a single sectorial molar. The molar teeth erupt gradually and the fourth molar may not erupt for three to four years. There is a lack of sexual dimorphism in the bettongs.

Distribution

The family is confined to coastal Australia in mainly the southern half, though B. tropica is found in northeastern Queensland. Bettongia gaimardi is found only on the island of Tasmania where it is still locally common. Potorous tridactlus is distributed from southern Queensland through New South Wales into most of Victoria as well as Tasmania. Potorous

longipes is only found in a very restricted area of Victoria while P. gilberti occurs only in Two People's Bay Nature Reserve, Western Australia. Bettongia lesueur is found on a few islands off the west coast of Western Australia and B. penicillata is found in pockets in southwest Western Australia and has been translocated to a number of islands off South Australia. Bettongia lesueur is restricted to only three islands of the west coast of Western Australia. Aepyprymnus is found only in New South Wales and Queensland.

Habitat

Most potoroids live in forest or woodland areas dominated by eucalyptus species. However, in the recent past, B. lesueur and B. pencillata lived over much of arid Australia. Bettongia lesueur, the burrowing bettong, lives in warrens that can be in sandy dunes. Potoroos tend to live in wetter forest areas than the bettongs, which prefer the more open forest that is better suited to their high hopping gait.

Behavior

Not a great deal of behavioral studies have been carried out on this nocturnal group. They are generally solitary, though some bettong males and females may cohabitate for short periods after mating. Males regularly check up on females living in their home range by inspecting their pouch and/or urogenital regions. This allows males to be aware of the reproductive status of the female and the imminence of estrus. Males can be aggressive towards other males, which generally takes the form of lashing out with their hind feet. Animals that are anxious often display a sinuous movement of the tail. Female bettongs not in estrous can also be aggressive towards unwelcome males, lashing out with their hind feet while lying on their side. Mating takes place usually only on the night of estrus and involves rear-entry while the male holds the female with his forelimbs around her flank. He may also hold on to her neck with his teeth. Intromission is usually of a few seconds duration but may occur several times in a night. This group makes few vocalizations, though females make a clucking-like sound to attract their young to the pouch. Anxious animals make a vocalization with an explosive expelling of air.

Feeding ecology and diet

The bettongs and potoroos are mainly fungivores, eating a large proportion of the fruiting bodies of underground (hypogeous) fungi. In order to accomplish this, it is necessary that they have a well-developed sense of olfaction; a large proportion of their cortex is devoted to this. Animals dig with their forefeet to access their diet. The well-developed fore-stomach of potoroids allows them to have sufficient time to digest the fungi and the gut flora/fauna assist in providing essential amino acids that may be absent from the diet. Animals can exist almost exclusively on fungi, which provide a nourishing diet high in both protein and lipid. The fungi grow on the roots of eucalyptus and other native trees and their spores are activated during passage through the bettong's gut, thereby allowing germination at the site of defecation.

Reproductive biology

Rat-kangaroos are probably polygynous and have a reproductive biology quite similar to that of their larger relatives, the kangaroos and wallabies. After a short gestation, usually about three weeks, the neonate crawls unaided to the pouch where it attaches to one of the four teats. On that night the mother comes into estrous, termed a postpartum estrus, and mates again. The resultant fertilized egg develops only to the blastocyst stage of about 100 cells before becoming dormant, termed embryonic diapause. It remains in the uterus until it is reactivated near the end of pouch development of the previous young. Then, usually on the same night that the large offspring finally vacates the pouch, the new offspring is born. Again, the mother will come into postpartum estrus and mate again. Thus, the rat-kangaroo can have three different generations at the same time: one young out of the pouch still suckling from her teat, one newborn young in the pouch, and one dormant embryonic stage in her uterus. All species give birth to one young at a time. The pouch contracts after the large offspring leaves the pouch, preventing its return and thereby protecting the newborn smaller young. The milk suckled by the young in the pouch is constantly changing its composition from a dilute milk low in protein and lipid but high in carbohydrate to one that becomes more concentrated and high in lipid and low in carbohydrate.

Conservation status

Bettongia tropica, Gilbert's potoroo, and the long-footed potoroo are listed as Endangered in the Environment Protection

and Biodiversity Conservation Act 1999 of the Commonwealth of Australia. Bettongia lesueur and the long-nosed potoroo in southeast Australia are listed as Vulnerable. The IUCN lists Gilbert's potoroo as Critically Endangered, the long-footed potoroo and northern bettong as Endangered, boodie as Vulnerable, brush-tailed bettong as Lower Risk/Conservation Dependent, and the Tasmanian bettong as Lower Risk/Near Threatened.

Significance to humans

Although rat-kangaroos are attractive animals, they have little significance in either a cultural or agricultural context.

Species accounts

List of Species

Tasmanian bettong

Bettongia gaimardi

taxonomy

Bettongia gaimardi (Desmarest, 1822), Port Jackson, New South Wales, Australia.

other common names

English: Bettong, rat-kangaroo, wallaby-rat; French: Kangourou-rat de Tasmanie; Spanish: Canguro-rata de Tasmania.

physical characteristics

Head and body length 12–13 in (31–33 cm); weight 4–6 lb (1.5–2.2 kg). Coat color is gray-brown above, light below. Its long tail has a white tip.

distribution

Eastern Tasmania and Australia.

habitat

Open sclerophyll forest and woodland; often with a rocky substrate.

behavior

Usually seen singly, nocturnal. Carries nest material in mildly prehensile tail. Males and females are aggressive.

feeding ecology and diet

The diet is composed of underground fungi.

reproductive biology

Probably polygynous. Breeds continuously; single young born after gestation of 21 days; pouch life of 105 days and mature by one year. Mothers have embryonic diapause. Lactation lasts for approximately 22 weeks.

conservation status

Extinct on mainland Australia; listed by the IUCN as Lower Risk/Near Threatened.

significance to humans

None known.

Long-nosed potoroo

Potorous tridactylus

taxonomy

Potorous tridactylus (Kerr, 1792), Sydney, New South Wales, Australia.

other common names

English: Potoroo, rat-kangaroo.

physical characteristics

Head and body length 13.3–16 in (34–38 cm); weight females:1.5–3 lb (660–1,350 g; males: 1.6–3.6 lb (740–1,640 g). Fur color is dark gray above, paler below. Its tapering tail has a white tip.

distribution

Southeast Australia and Tasmania.

habitat

Coastal heath and dry and wet sclerophyll forests. Often makes forays in the undergrowth.

behavior

Lives solitarily or in pairs; males are territorial. Unobtrusive and secretive. May be monogamous or polygynous.

feeding ecology and diet

Mainly eats underground fungi.

reproductive biology

Gestation lasts approximately six weeks and pouch life is 125 days. Mother has embryonic diapause and mates shortly after giving birth.

conservation status

Not threatened.

significance to humans

Cell line used in genetic studies.

Brush-tailed bettong

Bettongia penicillata

taxonomy

Bettongia penicillata Gray, 1837, New South Wales, Australia.

other common names

English: Woylie; French: Bettongie à queue touffue, kangourou-rata à queue touffue; Spanish: Canguro-rata colipeludo.

physical characteristics

Head and body length 11.8–16 in (30–38 cm), tail 12 in (31 cm); weight 2.6 lb (1,300 g). Coat is darker above and paler below. Similar in appearance to other bettongs, but tail has a small crest.

distribution

Southwestern Australia; successfully reintroduced into South Australia.

habitat

Open sclerophyll forest and woodland; reenters areas soon after forest fires.

behavior

Nocturnal, solitary living in an above-ground nest.

feeding ecology and diet

Mainly feeds on the fruiting bodies of underground fungi.

reproductive biology

Similar to other bettongs; gestation is 21 days and pouch life 100 days. Probably polygynous or promiscuous.

conservation status

Listed as Lower Risk/Conservation Dependent. It is threatened by the fox and the cat in some areas. Increased numbers have come via translocations.

significance to humans

None known.

Northern bettong

Bettongia tropica

taxonomy

Bettongia tropica Wakefield, 1967, Queensland, Australia.

Bettongia tropica Aepyprymnus rufescens Potorous longipes

other common names

None known.

physical characteristics

Head and body length 15.3 in (39 cm), tail 14 in (36 cm); weight 2.6–3.1 lb (1,200–1,400 g). Coat is darker above and paler below. Similar in appearance to other bettongs.

distribution

Northeastern coastal Queensland.

habitat

Tall wet sclerophyll forest along the edge of rainforest.

behavior

Nocturnal, solitary living in an above-ground nest.

feeding ecology and diet

Mainly feeds on the fruiting bodies of underground fungi and cockatoo grass.

reproductive biology

Similar to other bettongs; gestation is 21 days and pouch life is 106 days. Probably polygynous or promiscuous.

conservation status

Endangered, and threatened by the fox and the cat in some areas. Increased numbers have come via translocations.

significance to humans

None known.

Boodie

Bettongia lesueur

taxonomy

Bettongia lesueur (Quoy and Gaimard, 1824), Dirk Hartog Island, Western Australia, Australia.

other common names

English: Burrowing bettong; French: Bettongie de Lesueur, kangourou-rat de Lesueur; Spanish: Canguro-rata de Lesueur.

physical characteristics

Head and body length 15.7 in (40 cm), tail 11.8 in (30 cm); weight 3.3 lb (1,500 g). Coat is darker above, paler below. Similar to other bettongs, no crest on thickish tail.

distribution

Several islands off the west coast of Western Australia; translocated to several areas on the mainland of Western Australia and South Australia.

habitat

Semi-arid coastal sandy areas where it lives in burrows.

behavior

Nocturnal, solitary, living in burrow, occasionally extends into warrens.

feeding ecology and diet

Omnivorous, eating fruit and fungi.

reproductive biology

Similar to other bettongs; gestation lasts 21 days and pouch life is about 115 days. Probably polygynous or promiscuous.

conservation status

Listed as Vulnerable, due to the small area in which it lives.

significance to humans

None known.

Gilbert's potoroo

Potorous gilbertii

taxonomy

Potorous gilbertii Gould, 1841, southwest Australia.

other common names

None known.

physical characteristics

Head and body length 13.3–15 in (34–38 cm); tail 9 in (23 cm); weight 2.2 lb (1000 g). Appearance similar to other potoroos, tail not well furred compared to body.

distribution

Resticted areas near Two People's Bay Nature Reserve, Western Australia.

habitat

Not well-described, open areas but foraging in areas with denser cover.

behavior

No data available.

feeding ecology and diet

Feeds on underground fungi.

reproductive biology

Little known, likely to be similar to long-nosed potoroo. May be monogamous.

conservation status

Listed as Critically Endangered, due to its small population size.

significance to humans

None known.

Long-footed potoroo

Potorous longipes

taxonomy

Potorous longipes Seebeck and Johnston, 1980, Victoria, Australia.

other common names

None known.

physical characteristics

Head and body length 15.7 in (40 cm), tail 12.6 in (32 cm); weight 3.3–5 lb (1.5–2.3 kg). Similar to other potoroos, but larger with hind foot longer than head.

distribution

Limited to two areas in northeastern Victoria and one in southeastern New South Wales.

habitat

Dry and wet sclerophyll forests, temperate rainforest, and montane forest.

behavior

No data available.

feeding ecology and diet

Fungivorous, eating the fruiting bodies of hypogeous fungi.

reproductive biology

May be monogamous. Gestation approximately 25–38 days, though this is not clear; pouch life 140–150 days.

conservation status

Listed as Endangered, due to its fragmented populations.

significance to humans

None known.

Rufous bettong

Aepyprymnus rufescens

taxonomy

Aepyprymnus rufescens (Gray, 1837), New South Wales, Australia.

other common names

English: Rufous rat-kangaroo.

physical characteristics

Head and body length 15 in (38 cm), tail 14 in (36 cm); weight 6.6–7.7 lb (3,000–3,500 g), females larger than males. Largest member of the family, reddish brown coloring and hairy muzzle.

distribution

Northeastern Queensland to northeastern New South Wales. Also found on the New South Wales-Victoria border.

habitat

Open sclerophyll forest and woodland.

behavior

Nocturnal, solitary animals living in a nest by day. Males can be aggressive toward each other.

feeding ecology and diet

Mainly fungivorous.

reproductive biology

Similar to other bettongs. Gestation 23 days and pouch life about 114 days. Has loose polygynous interactions.

conservation status

Not threatened.

significance to humans

None known.

Resources

Books

Rose, R. W. "Reproductive Biology of Rat Kangaroos." In Kangaroos, Wallabies and Rat Kangaroos, edited by G. Grigg, P. Jarman, and I. D. Hume. New South Wales: Surrey Beatty & Sons, 1989.

Strahan, R., ed. Complete Book of Australian Mammals. Sydney: Angus & Robertson Publishers, 1995.

Walton, D., ed. Mammals of Australia. Canberra: Bureau of Fauna and Flora, 1988.

Periodicals

Rose, R. W. "Reproductive Energetics of Two Tasmanian Rat-kangaroos (Potoroinae: Marsupialia)." Symposium of the Zoology Society of London 57 (1987): 149–165.

Rose, R. W., and R. B. Rose. "The Tasmanian Bettong Bettongia gaimardi." Mammalian Species 584D (1998).

Randolph W. Rose, PhD