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Petropseudes dahlirock ringtail possum

By Robert Stroede

Geographic Range

Rock ringtail possums are found in rocky terrain, usually sandstone outcroppings, in a small portion of northern Australia. The species has a wide distribution in northern Australia. Most commonly the species is found in the Northern Territory, Kimberley, Katherine, and Queensland. (Collett, 1995; Keast, 1968; Martin, 2002; Runice, 2000a; Runice, 2000b)

Habitat

Rock ringtail possums live in rocky, sandstone outcrops where they are sheltered during the day. At night they move out of their sheltered rock crevices to feed in the trees within the area, often traveling no further than 10 meters from their dens. These rocky areas usually are surrounded by flatter, lowland areas. The rocky encampments have increased water holding potential and are sometimes flooded in areas. (Collett, 1995; Martin, 2002; Runice, 2000a; Runice, 2000b)

Physical Description

Rock ringtail possums are small, stocky possums, similar in size to a small rabbit. The pelage is grey to reddish-grey on the back and a lighter, cream color on the underside. There is a dark stripe down the middle of their backs. The coat is long and thick. The tail is unique in that it is furred only half-way down, it lacks scales on the unfurred portion of the tail, unlike some of their close relatives. Rock ringtail possums have small, rounded ears. They have white hair in patches both above and below the eyes and underneath the ears. Rock ringtail possums live in rocky areas and have developed many adaptations to a more terrestrial lifestyle than many of their relatives. They have shorter legs, claws, and tails. As in other possums, the tail is prehensile. (Collett, 1995; Martin, 2002; Runice, 2000b)

  • Sexual Dimorphism
  • female larger
  • Range mass
    1280 to 2000 g
    45.11 to 70.48 oz
  • Range length
    334 to 383 mm
    13.15 to 15.08 in

Reproduction

Petropseudes dahli is one of few obligate monogamous marsupial species. Females live in their home range with one male. Scent posts are used commonly by the species to define home range and to mark territories. Family groups are tightly knit and consist of the mother, father, and one or occasionally two offspring. Young help with raising their younger siblings. (Collett, 1995; Runice, 1999)

There does not appear to be a restricted breeding season. There is normally one offspring, with occasionally two. No gestation period information is available for the species but close relatives have gestation periods from 16 to 30 days. Females have a large pouch with two teats where the new offspring spends its first five weeks. The current year's offspring are often found on the back of their parent's or nearby after leaving the safety of their mothers pouch. Previous offspring will commonly stay with the family unit to assist in rearing the next offspring. (Collett, 1995; Martin, 2002; Runice, 1999; Runice, 2000b)

  • Breeding interval
    Rock ringtail possums breed twice yearly.
  • Breeding season
    There does not appear to be a well defined breeding season. Offspring have been seen from March to September.
  • Range number of offspring
    1 to 2
  • Average weaning age
    5 weeks
  • Average time to independence
    7 months
  • Average age at sexual or reproductive maturity (female)
    7 months
  • Average age at sexual or reproductive maturity (male)
    7 months

There is an extensive amount of parental care in this species. Rock ringtail possums live in tight knit family groups. Care of young is undertaken by both parents and young of the previous breeding effort. Care of young is divided nearly equally between the two parents after weaning. Prior to weaning the offspring spends its time in its mothers pouch receiving nourishment from her milk. After exiting the pouch, both parents spend time grooming, resting with, and greeting their young. Mother and father both also practice several protective behaviors. Both parents spend time watching for predators, beating their tails, vocalizing, and keeping young relatively close. Females nursing young in their pouches can become defensive, on occassion even towards their mate. This behavior ranges from swinging of limbs towards counterpart or making growls or grunts. Mothers may also show some slight aggression towards subadults if they interfere with her activities or young. (Collett, 1995; Martin, 2002; Runice, 1999; Runice, 2000b)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-independence
    • protecting
      • male
      • female
  • post-independence association with parents
  • extended period of juvenile learning

Lifespan/Longevity

There is no information on longevity of rock ringtail possums. A closely related species, Leadbeater's possums (Gymnobelideus leadbeateri), live more than 10 years in captivity. In the wild this same species has a maximum longevity of 5 years. (McKay, 1989)

Behavior

Rock ringtail possums are social, living in tight knit family groups. These groups are usually made up of about 4 individuals, although group sizes of two 2 to 10 individuals are reported. They spend the majority of their days sheltered within rock piles or crevices between the rocks of the sandstone outcrops they call home. After dark these animals move from their rocky habitats into the trees nearby, where they feed. Rock ringtail possums are secretive and avoid contact and confrontation. They are primarily terrestrial, moving into the trees only to feed. This distinguishes them from their close, mostly arboreal relatives. (Collett, 1995; Martin, 2002; McKay, 1989; Runice, 2000b; Collett, 1995; Martin, 2002; McKay, 1989; Runice, 2000b; Collett, 1995; Martin, 2002; McKay, 1989; Runice, 2000a; Runice, 2000b)

  • Range territory size
    0.005 to .012 km^2
  • Average territory size
    0.009 km^2

Home Range

Both sexes have about the same home range size. Average home range is 0.9 hectares, with home ranges ranging in size from 0.5 to 1.2 hectares. The average density in these home ranges is 0.4 possums per hectare. (Collett, 1995; Runice, 2000b; Collett, 1995; Runice, 2000b; Collett, 1995; Runice, 2000a; Runice, 2000b)

Communication and Perception

Rock ringtail possums use chemical signals to communicate most extensively. Adult possums have an important scent gland on the chest region and males have a 2 cm diameter paracloacal gland. They maintain scent posts that are visited commonly. These scent posts develop a thick, lacquer-like coating. Rock ringtail possums use both urine and feces to mark these areas. These possums are also thought to mark tree branches using their paracloacal gland. Rock ringtail possums have been observed striking their tails against rocks, possibly as a form of communication. The species also is able to make grunts and growls that serve as auditory communication. (Collett, 1995; Runice, 2000a)

Food Habits

Rock ringtail possums feed in trees, they commonly feed within 100 meters of their rocky outcrop homes. This species eats leaves, fruit, blossoms, flowers, and occasionally feed on termites. THe blossoms of Darwin woollybutt, Eucalyptus miniata, and Darwin stringybark are all eaten by rock ringtail possums. Fruit is eaten from the following species: Zyziphus oenoplia, Vitex glabrata, Terminalia fernandiana, and Owenia vernicosa. Leaves eaten include: Flagelleria indica, Pouteria sericea, and vine reedcane. (Collett, 1995; Martin, 2002)

  • Animal Foods
  • insects
  • Plant Foods
  • leaves
  • fruit
  • flowers

Predation

In order to avoid predations, rock ringtail possums spend a large amount of time participating in sentinel behavior. They will perch on branches or ledges and scan the area for danger. Rock ringtail possums will flee from predators to their more familiar rocky habitats where they will hide in rock crevices. When confronted they may make a low growl. Rock ringtail possums also beat their tails vigorously against tree branches, causing the entire tree to shake in order to attempt to deter predators and to warn others. Potential predators of rock ringtail possums include dingos, owls, quolls, feral cats and dogs, olive pythons, Oenpelli rock pythons, and humans. (Collett, 1995; Runice, 2000a; Runice, 2000b)

Ecosystem Roles

Rock ringtail possums may disperse seeds through their fruit eating habits. They may also influence termite populations and act as prey for regional predators. (Collett, 1995; Runice, 2000a)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Aboriginal peoples of the area used to capture this species. They utilized the animal both for its fur and as a food source. Rock ringtail possums are also important in education and research. (Runice, 2000b)

  • Positive Impacts
  • food
  • body parts are source of valuable material
  • research and education

Economic Importance for Humans: Negative

Petropseudes dahli has likely been affected by human induced habitat fragmentation and its numbers have decreased significantly. The species is listed as a priority species in western Australia and management efforts may affect forestry management and development practice. (Collett, 1995; McKay, 1989)

Conservation Status

Petropseudes dahli is listed as priority species in Western Australia. (Australian Wildlife Conservancy, 2006)

Other Comments

Petropseudes dahli mothers may actually allow her young to move from branch to branch by using her body as a bridge. This has never been seen in another possum. This species also exhibits the uncommon habit of embracing their young, which is only seen in apes. They are also the only marsupial ever seen utilizing termite mounds. (Martin, 2002; Martin, 2002)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Robert Stroede (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.

Glossary

Australian

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

World Map

acoustic

uses sound to communicate

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.

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

cooperative breeder

helpers provide assistance in raising young that are not their own

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.

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

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).

monogamous

Having one mate at a time.

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

scent marks

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

scrub forest

scrub forests develop in areas that experience dry seasons.

sedentary

remains in the same area

sexual

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

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

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.

year-round breeding

breeding takes place throughout the year

References

Australian Wildlife Conservancy, 2006. "Australian Wildlife Conservancy" (On-line). Threatened Wildlife List: Rock ringtail possum Petropseudes dahli . Accessed November 29, 2006 at http://www.australianwildlife.org/threatenedwildlifelist.asp?WID=617.

Collett, 1995. Rock Ringtail Possum. Pp. 242-243 in R Strahan, ed. Mammals of Australia, Vol. Volume 1, Edition 2 Edition. Chatswood, New South Wales: Reed Books.

Crowe, O., I. Hume. 1997. Morphology and Function of the Gastrointestinal Tract of Australian Folivorous Possums. Australian Journal of Zoology, Volume 45/ Issue 4: 357-368.

Keast, A. 1968. The Quarterly Review of Biology; Evolution of Mammals on Southern Continents, IV. Austrailian Mammals:Zoogeography and Evolution. Austrailian Mammals, Vol. 43/ No. 4: 373 - 405.

Martin, S. 2002. Declining mammals of the savannas. Tropical Topics, No. 75/October 2002: 1-8.

McKay, G. 1989. Family Petauridae. Pp. 1-23 in D Walton, B Richardson, eds. Fauna of Australia, Vol. Vol 1, B Edition. Canberra: Austrailian Government Publishing.

McKenzie, N. 1981. Mammals of the Phanerozoic South-West Kimberley, Western Australia: Biogeography and Recent Changes. Journal of Biogeography, Vol. 8/ No. 4: 263-280. Accessed November 29, 2006 at http://links.jstor.org/sici?sici=0305-0220%28198107%298%3A4%3C263%3AMOTPSK%3E2.0.CO%3B2-F.

Runice, M. 2000. Biparental care and obligate monogamy in the rock-haunting possum, Petropseudes dahli, from tropical Australia. Animal Behaviour, Vol. 59/Part 5: 1001 - 1008.

Runice, M. 1999. Movements, dens and feeding behaviour of the tropical scaly-tailed possum(Wyulda squamicaudata). Wildlife Research, Vol. 26/Issue 3: 367-373.

Runice, M. 2000. Adventures at Possum Rock. Nature Australia, Vol 26/ No 8: 30-45.

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