Possums and cuscuses

(Phalangeridae)

Class Mammalia

Order Diprotodontia

Suborder Phalangerida

Family Phalangeridae

Thumbnail description
Small- to medium-sized marsupials with clawed, grasping hands and feet with five digits, a long, prehensile tail with a naked underside, and a slightly elongate muzzle

Size
Total length 23.6–47.2 in (60–120 cm); weight 2–22 lb (1–10 kg)

Number of genera, species
6 genera; 26 species

Habitat
Forest and woodlands

Conservation status
Endangered: 2 species; Vulnerable: 2 species; Lower Risk/Near Threatened: 1 species; Data Deficient: 5 species

Distribution
Australasia east of Wallace's Line, including Sulawesi, Timor, the Moluccas, New Guinea, and many closely adjacent islands, as well as Australia and Tasmania; introduced to New Zealand

Evolution and systematics

The phalangers (family Phalangeridae) are classified into six distinctive genera. The most diverse genus, Phalanger, comprises a group of medium-sized, soft-furred species that generally possess a dorsal stripe. Phalanger is primarily a New Guinean genus, but one species extends to northern Australia and several others occur throughout the Moluccan islands of Indonesia. Spotted cuscuses (genus Spilocuscus) are the most beautiful of the phalangers, with striking coats colored with combinations of red, white, black, brown, and yellow; they occur throughout New Guinea and on several adjacent islands, as well as in far northeastern Australia. The small-bodied species of Strigocuscus and the very large bear cuscuses (Ailurops) both occur only on Sulawesi and closely adjacent islands. Species of Phalanger, Spilocuscus, Strigocuscus, and Ailurops are all called cuscuses, whereas the remaining two genera within the family, Trichosurus and Wyulda, are called possums. Both of these latter genera are endemic to Australia. The five species of brush-tailed possums (Trichosurus) are (or were, until quite recently) distributed across most the Australian continent, while the rare scaly-tailed possum (Wyulda squamicaudata) occurs only in a small area of far northwestern Australia and is classified in a genus unique to itself. The phalanger fossil record extends back roughly 20 million years, to the middle Miocene, when three phalangerid genera (Trichosurus, Wyulda, and possibly Strigocuscus) occurred in northern Australia. The fossil history of phalangerids outside of mainland Australia is very poorly known. Within the family, species of Trichosurus and Wyulda are clearly closely related to one another, as are those of Phalanger and Spilocuscus. However, the exact relationships of these two groups with one another and with Strigocuscus and Ailurops remain obscure. The phylogenetic position of the genus, Ailurops, is particularly controversial. Anatomical evidence strongly suggests that the bear cuscuses are the most primitive phalangers—the first offshoot on the phalanger family tree. However, evidence from molecular studies does not support this hypothesis thus far. Future studies based on analysis of DNA will hopefully offer greater resolution of relationships within the family.

Physical characteristics

Phalangers are small- to medium-sized marsupials. The smallest phalanger (Strigocuscus celebensis) weighs 2 lb (1 kg)

or less, and the largest species (Ailurops ursinus) weighs up to 22 lb (10 kg); but most species of the family weigh between 3 and 6 lb (1.5–3 kg). The pelage is generally soft and dense. Color varies widely, especially in the spotted cuscuses and the beautifully mottled Woodlark cuscus (Phalanger lullulae), but most species are brown or gray, often with a dark dorsal stripe running down the center of the head and back. In all species except those of the genus, Trichosurus (which has a superficially dog- or fox-like appearance), the ears are reduced and often wholly or partially hidden in the soft fur. The feet have five digits, all of which support a large claw, except the hallux (big toe). The hallux is opposable to the remaining digits of the hind foot, and the first two digits of the forefoot oppose the remaining three, allowing the feet to grasp branches firmly while climbing. The second and third digits of the hindfoot are reduced and partially united by skin to form a single functional digit with two claws (a condition called syndactyly) that is used as a hair comb. The tail is long and prehensile, with the distal part generally naked (only on the underside in the bushy-tailed species of Trichosurus) and (especially in

older males) covered with small tubercles that give it a strongly rugose surface.

Distribution

Phalangers occur naturally throughout New Guinea, Australia, and Tasmania, and on a number of Indonesian islands (Sulawesi and the Moluccas). Cuscuses were prehistorically introduced from New Guinea to many nearby islands (including Timor and the Bismarck and Solomon Archipelagos), and the common brush-tailed possum was introduced to New Zealand from Tasmania and mainland Australia in the mid-nineteenth century.

Habitat

All phalangers are well adapted for climbing and are highly reliant on trees, which they use for shelter, foraging, or both. Most species are inhabitants of rainforest, although the scalytailed possum occurs in rocky areas in broken sandstone country

in northwestern Australia, and the remarkably versatile common brushtail possum (Trichosurus vulpecula) occupies a varied range of habitats and is common even in urban areas. Phalangers reach their greatest diversity in mid-montane rain-forest in central New Guinea, where up to five species of the family coexist.

Behavior

Most phalangers are nocturnal, but the two largest species (the Sulawesi bear cuscus, Ailurops ursinus, and the black-spotted cuscus, Spilocuscus rufoniger) are often active by day. Most species are arboreal, living in tree hollows and feeding in the forest canopy. However, one species, the ground cuscus (Phalanger gymnotis) of New Guinea, exhibits a more terrestrial lifestyle; it lives in underground burrows and travels along the rainforest floor. However, even the ground cuscus is a very good climber, ascending into trees to feed on fruit at night. The social behavior of most phalangers has received little study to date. Several species seem to form male-female pairs (such as the small Sulawesi cuscus, Strigocuscus celebensis, and the mountain brush-tailed possum, Trichosurus caninus), but the majority of species are solitary. Males of most species are aggressive toward one another and cannot be kept together in captivity.

Feeding ecology and diet

Though phalangers are almost exclusively herbivorous, the kinds of plants favored can vary greatly from species to species. Some phalangers, including the Sulawesi bear cuscus (Ailurops ursinus), are largely folivorous, while others such as the ground cuscus and the small Sulawesi cuscus are primarily frugivorous. Both leaves and fruit probably form high proportions of the diet of most species, especially in tropical forests; other food sources such as flowers, bark, pollen, and fungi may also be utilized in small quantities. The common brush-tailed possum is the most ecologically versatile phalanger and probably has the most generalized diet; its diet may change drastically in different local habitats, variably comprising large proportions of leaves (including some defended by highly toxic compounds), grasses and herbs, ferns and mosses, and fruits.

Reproductive biology

Although many species are monogamous, most are probably promiscuous. Female phalangers have a forward-oriented pouch with two or four teats. Adult females generally produce one or two litters per year. Up to three or four young may be born, but only one is usually reared, although in the northern common cuscus (Phalanger orientalis), twins are commonly raised. Gestation is 20 days or less; like other marsupials, neonates are born very small and unfurred. Infants are weaned and exit the pouch between five and eight months, after which they are carried on their mother's back.

Conservation status

Several phalanger species are in danger of extinction. Four rare species with small geographic ranges are particularly threatened: the scaly-tailed possum of northwestern Australia, the Telefomin cuscus (Phalanger matanim) of central New Guinea, the black-spotted cuscus of northern New Guinea, and the yellow bear cuscus (Ailurops melanotis) of the Sangihe and Talaud Islands in eastern Indonesia. Other species that are locally common but restricted to single islands, such as the Waigeo cuscus (Spilocuscus papuensis), the Gebe cuscus (Phalanger alexandrae), and the Woodlark cuscus, are also worthy of conservation attention. However, many other phalangers, including the northern common cuscus (Phalanger orientalis) and the common brushtail possum, are both geographically widespread and locally common and are presently under no threat.

Significance to humans

Cuscuses are an important source of meat for people throughout the New Guinea region, and they are widely hunted. However, in some areas of Indonesia such as the Sula Islands in the western Moluccas, cuscuses are not eaten in accordance with religious traditions. Common brushtail possums have unfortunately become a significant environmental and agricultural pest in New Zealand, where they have been introduced and are now widespread and common.

Species accounts

List of Species

Sulawesi bear cuscus

Ailurops ursinus

taxonomy

Ailurops ursinus (Temminck, 1824), Sulawesi, Indonesia.

other common names

German: Bärenkuskus.

physical characteristics

A large and powerful phalanger (up to 22 lb [10 kg]), with long limbs and black fur often tipped with yellow.

distribution

A. u. ursinus: lowlands of Sulawesi, Peleng, and some adjacent smaller islands; and A. u. togianus: Togian Islands.

habitat

Lowland and mid-elevation rainforest.

behavior

Generally occurs in groups of two to four individuals. It is arboreal, living and feeding in the forest canopy, and may be active at any time, day or night.

feeding ecology and diet

Largely folivorous, but flowers and fruits make up a small part of the diet.

reproductive biology

Very little is known. Females give birth once or twice a year, and weaning has been reported to occur at eight months.

conservation status

Possibly threatened; classified as Data Deficient.

significance to humans

As a very large phalanger, this species is a target of hunting, and is sometimes encountered as food in markets and restaurants in Sulawesi.

Small Sulawesi cuscus

Strigocuscus celebensis

taxonomy

Strigocuscus celebensis (Gray, 1858), Sulawesi, Indonesia.

other common names

German: Celebeskuskus.

physical characteristics

This is the smallest phalanger, weighing 2 lb (1 kg) or less. The overall coloration is pale buff, a dorsal stripe is lacking, and the naked part of the tail is very sparsely haired.

distribution

S. c. celebensis: southern and central Sulawesi; S. c. feileri: north Sulawesi; and S. c. sangirensis: Sangihe Islands north of Sulawesi.

habitat

Rainforest.

behavior

Arboreal and nocturnal, and apparently occurs in pairs.

feeding ecology and diet

Thought to be primarily frugivorous.

reproductive biology

Little is known; probably monogamous.

conservation status

Uncertain; classified as Data Deficient.

significance to humans

None known.

Common spotted cuscus

Spilocuscus maculatus

taxonomy

Spilocuscus maculatus (Desmarest, 1818), Vogelkop, Irian Jaya, Indonesia.

other common names

German: Tüpfelkuskus.

physical characteristics

A relatively large phalanger (weighing up to 13.2 lb [6 kg]) with large round eyes and very small ears. The coat is colorful but very variable, and differs characteristically both between the sexes and among the four subspecies. Males may be pure white or spotted with red-orange, black, or gray, while females are often unspotted, with an unbroken black or gray "saddle" on the back.

distribution

S. m. maculatus: northern New Guinea; S. m. chrysorrhous: southern New Guinea and the central Moluccas; S. m. goldiei: southeastern New Guinea; and S. m. nudicaudatus: tropical northern Australia.

habitat

Lowland rainforest, from sea level to 3,900 ft (1,200 m).

behavior

Nocturnal and arboreal, rarely descending to the ground. It has an unusually low metabolic rate, and its movement through the trees is often relatively slow.

feeding ecology and diet

Predominantly leaves and fruit.

reproductive biology

Females have four mammae. Two to four young have been reported in a litter, but a single young is most common. Infants exit the pouch six to seven months after birth. It is not known whether breeding is seasonal or takes place year-round. The estrous cycle lasts four weeks; at the peak of the cycle, females are highly vocal. Mating system is not known.

conservation status

Not threatened.

significance to humans

Widely hunted and often transported and sold as a pet or as food in local markets in New Guinea.

Black-spotted cuscus

Spilocuscus rufoniger

taxonomy

Spilocuscus rufoniger (Zimara, 1937), Morobe Province, Papua New Guinea.

other common names

German: Schwarzgeflecktkuskus.

physical characteristics

A very large species, brightly colored; males with a jet black "saddle" on the lower back, females with black and white spotting on the lower back.

distribution

Northern New Guinea.

habitat

Primary (undisturbed) lowland rainforest, from sea level to 3,900 ft (1,200 m).

behavior

Arboreal; apparently largely nocturnal, but occasionally active during the day.

feeding ecology and diet

Nothing is known.

reproductive biology

Nothing is known.

conservation status

This large-bodied species has undergone a widespread decline across its range in recent decades, and is listed as Endangered.

significance to humans

Hunted for food and for its beautifully colored skin. Hunting this species remains a male rite of passage in some parts of New Guinea.

Ground cuscus

Phalanger gymnotis

taxonomy

Phalanger gymnotis (Peters and Doria, 1875), Aru Islands, Indonesia.

other common names

German: Gleichfarbkuskus, Bodenkuskus.

physical characteristics

Color light to dark gray, with a distinct dorsal stripe, prominent ears, and a coarsely tuberculated tail.

distribution

P. g. gymnotis: Aru Islands; and P. g. leucippus: mainland New Guinea.

habitat

Occurs in rainforest from sea level up to 8,900 ft (2,700 m), but is most common at intermediate elevations.

behavior

This species is unique among cuscuses in that it occupies burrows in holes in the ground, often under trees, along streams,

or in caves. It is generally nocturnal, and forages both on the ground and in trees. New Guinea hunters claim that it suns itself outside its burrow in the morning, and that females may carry fruit to the burrow in their pouches.

feeding ecology and diet

Primarily frugivorous, but also eats leaves and, on occasion, small vertebrates and insects.

reproductive biology

Both sexes are generally solitary, and breeding is continuous year-round. A single young is most common, and infants leave the pouch permanently five to seven months after birth. Mating system is not known.

conservation status

Common in many parts of New Guinea and probably not threatened, but classified as Data Deficient.

significance to humans

Widely hunted with dogs throughout New Guinea, and is an important figure in tribal folklore in some areas.

Common brushtail possum

Trichosurus vulpecula

taxonomy

Trichosurus vulpecula (Kerr, 1792), Sydney, Australia.

other common names

French: Phalanger-renarrd; German: Gewöhnlicher Fuchskusu.

physical characteristics

Has a woolly coat and a thick, well-furred tail. Size and coloration are highly variable; individuals may be gray, black, reddish, brown, or white. The ears are large, with a narrowly rounded tip.

distribution

Occurs throughout eastern and southwestern Australia and in Tasmania and, until recently, it occupied much of central Australia. It is now common in New Zealand, where it was introduced about 150 years ago.

habitat

Usually forests and woodlands, but this species is extremely versatile and may occupy many different habitat types, including semiaraid areas devoid of trees and suburban and urban areas.

behavior

Generally solitary, nocturnal, and arboreal. It most commonly nests in tree hollows, but may also nest in roofs or in burrows in the ground. In areas of low density, adults may aggressively defend discrete territories, but where population density is high, home ranges of individuals may overlap widely.

feeding ecology and diet

A wide variety of plants is eaten, and occasionally small animals and insects are taken.

reproductive biology

Breeding occurs year-round, although births peak in fall and spring. Females usually produce one or, less commonly, two litters per year. After a gestation period of about 18 days, one young is usually born, which leaves the pouch after six to seven months. Probably promiscuous.

conservation status

As it is very common in many areas, the brush-tailed possum is considered to be not threatened, although it has undergone a wide decline in central Australia and may be declining in southwest Australia.

significance to humans

Because it is common in developed areas such as city parks and suburban backyards, this possum has a closer interaction with people than any other Australian mammal. Pelts of common brush-tailed possums have been widely trapped and sold for the fur trade in Australia. In many areas, it is considered an agricultural pest and a potential vector of disease, and it is a pest in both crops and native forest in New Zealand, where it is non-native.

Scaly-tailed possum

Wyulda squamicaudata

taxonomy

Wyulda squamicaudata Alexander, 1918, Wyndham, Western Australia, Australia.

other common names

German: Schuppenschwanzopossum, Schuppenschwanzkusu.

physical characteristics

Medium-sized; weight 3–6.5 lb (1.4–3 kg); overall color dull gray, with a flattened head, reduced claws, and a wholly naked tail with a white tail-tip and coarse scales.

distribution

Known only from the Kimberley region of northwestern Australia.

habitat

Occurs in rocky areas with trees in broken sandstone country.

behavior

More terrestrial than most phalangers, and shows a number of specializations for moving both on rocky ground and in trees. One captive individual was reported to hoard small caches of food such as nuts, and to make chattering vocalizations.

feeding ecology and diet

Nothing is known.

reproductive biology

Females breed once a year, and generally raise only a single young, which is born between March and August. Weaning occurs at about eight months. Mating system is not known.

conservation status

Best considered endangered, although it is currently classified by the IUCN as Lower Risk/Near Threatened.

significance to humans

None known.

Resources

Books

Flannery, Timothy F. Possums of the World: A Monograph of the Phalangeroidea. Sydney: GEO Productions, 1994.

Long, John, Michael Archer, Timothy Flannery, and Suzanne Hand. Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution. Baltimore: Johns Hopkins University Press, 2002.

Kristofer M. Helgen