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Phalanger orientalisgray cuscus

By Laura Merlo

Geographic Range

Phalanger orientalis is thought to have originated on New Guinea and then to have been distributed primarily by prehistoric humans to the range it currently occupies (Nowak, 1999). That range now includes the South West Pacific islands of Buru, Seram, the Solomon and Molucca Islands, northern New Guinea, and the Bismark Archipelago (Nowak, 1999) . Until recently, P. orientalis and P. intercastellanus (Southern Common Cuscus) were thought to belong to the same species (Flannery, 1995). P. intercastellanus inhabits northern Australia, the Aru Islands, and the Louisade Archipelago (Strahan, 1995).

Habitat

P. orientalis is resitricted to tropical rainforests and thick scrub in the South West Pacific (Nowak, 1999). They have also been spotted in gardens, probably due to the high abundance of edible plants (Flannery, 1995).

  • Range elevation
    0 to 1600 m
    0.00 to 5249.34 ft

Physical Description

P. orientalis, like others in the family Phalangeridae, is heavy and powerfully built (Nowak, 1999). The average mass is about 2.1 kg. This is slightly lower in females (Grizmek, 1990).

The tail is prehensile naked at the end. It is covered with horny papillae. The tail length varies from 28 to 42 cm (Grizmek, 1990). The male tail is completely white but female tails are white only on the tips.

In adult males, the thick, wooly fur ranges in color from white to medium or dark grey (Nowak, 1999). In adult females, the color ranges from reddish-brown to brownish-grey. The stomach area is commonly white. The male has a distinct yellowish chest gland. Usually a dark stripe runs from the head to the lower back. The young of this species are reddish-brown. (Flannery, 1995; Nowak, 1999)

The digits are of different lengths and are tipped by long, curved claws. Their paws are syndactylous, with the first and second digits opposable to the rest. The soles of their feet are naked and striated. The female pouch has four mammae (Nowak, 1999). The facial features include large eyes, long canines and a snout longer than that of Spilocuscus maculatus (Spotted Cuscus). The teeth are simple, low crowned and used for grinding (Flannery, 1995).

  • Range mass
    1.0 to 5.0 kg
    2.20 to 11.01 lb
  • Average mass
    2.1 kg
    4.63 lb
  • Range length
    35 to 55 cm
    13.78 to 21.65 in
  • Average length
    39 cm
    15.35 in

Reproduction

The gestation period for P. orientalis lasts around 13 days. Normally the females births twins, but the number of young ranges from one to three (Grizmek, 1990). Usually, one of the twins dies before weaning (Nowak, 1999). The weight at birth is less than 1 gram (Grizmek, 1990).

Normally, the reproductive cycle occurs only once a year. Mating and reproductive seasons are from June through October, though March and November births have been observed (Tyndale-Brisco, 1987).

Because P. orientalis has not been well studied, information on the reproctive behavior is sparse.

  • Breeding season
    June through October
  • Range number of offspring
    1 to 3
  • Average number of offspring
    2
    AnAge
  • Average gestation period
    13 days
  • Range weaning age
    not known (high) days

Behavior

P. orientalis is nocturnal, spending the day in a tree hollow. While foraging for food at night, it travels through the forest in a slow deliberate climb (Nowak, 1999). P. orientalis grips with three feet at a time and the tail wraps around the branch ready to hold weight. Ground travel -- though rare -- is characterized by a slow, bounding gait. If necessary, P. orientalis moves quickly through the canopy and even jump across gaps (Flannery, 1995).

P. orientalis is solitary and has been oberseved to be very intolerant of Spilocuscus maculatus (Spotted Cuscus) if they come in contact with one another. P. orientalis is more tolerant of humans, and it is commonly kept as a pet (Flannery, 1995).

Communication and Perception

Food Habits

P. orientalis climbs slowly through the rainforests and locates mainly leaves, tree seeds, fruit, buds and flowers on which they feed (Girzmek, 1990). It has been spotted eating the green fruit of the Red Cedar (Toona australis) and the buds and flowers of Corky Bark (Carallia brachiata). A paste derived from the seeds of the Black Bean Tree (Castanospermum australe) was found in the stomach of one animal. While in captivity it primarily eats leaves and fruit (Flannery, 1995).

Predation

P. orientalis had not been closely studied due to its secluded lifestyle. The following are a few specific predators that have been documented: White-bellied Sea-Eagle (Haliaeetus leucogaster) (Heinsohn, 2000), Amethystine (Morelia amethistina)(Flannery, 1995), Carpet Pythons (Morelia s. cheynei)(Flannery, 1995), and possibly Dasyurids (Grizmek, 1990). The assumption is that these and other species like them prey upon P. orientalis.

Ecosystem Roles

P. orientalis does not have any recorded ecological roles.

Economic Importance for Humans: Positive

In New Guinea, P. orientalis is hunted for food by native tribes, though this is rare (Flannery, 1995).

  • Positive Impacts
  • food

Conservation Status

Contributors

Laura Merlo (author), University of Michigan-Ann Arbor, Ondrej Podlaha (editor), University of Michigan-Ann Arbor.

Glossary

Australian

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

World Map

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

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.

female parental care

parental care is carried out by females

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.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

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

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season

sexual

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

solitary

lives alone

tactile

uses touch to communicate

tropical

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

viviparous

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

References

1990. Grizmek's Encyclopedia of Mammals. Volume 1. New York, NY: McGraw-Hill Publishing Company.

Flannery, T. 1995. Mammal of the South-West Pacific and Moluccan Islands. Chatswood, NSW: Reed Books as a part of Reed Books Australia.

Heinsohn, T. September 2000. Predition by the White-breasted Sea Eagle, Haliaeetus leucogaster, on phalangerid possums in New Ireland, Papua New Guinea. Emu - Austral Orinthology, 100(3): 245-246.

Nowak, R. 1999. Walker's Mammals of the World, 6th edition. Volume 1. Baltimore, MD: The Johns Hopkins University Press.

Nowak, R. 1997. "Walker's Mammals of the World Online 5.1" (On-line). Accessed 7 October 2001 at www.press.jhu.edu/books/walkers_mammals_of_the_world/marsupialia/marsupialia.phalangeridae.phalanger.

Stonehouse, B., D. Gilmore. 1977. The Biology of Marsupials. Baltimore, Md: University Parks Press.

Strahan, R. 1995. The Mammals of Australia. Chatswood, NSW: Reed Books for the Australian Museum Trust.

Tyndale-Biscoe, C., M. Renfree. 1987. Reproductive Physiology of Marsupials. New York, NY: Press Syndicate of the University of Cambridge.

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