Phalanger gymnotis
ground cuscus

Ground cuscuses (Phalanger gymnotis) are found on the islands of New Guinea, Yapen, Misool, Salawati and the Aru Islands. Although rare, they have also been sighted in southernmost regions of New Guinea. ("Ground Cuscus", 2004; Flannery, 2004; Wilson and Reeder, 2005)

Phalanger gymnotis occupies a variety of habitats including rainforests, caves and gardens. It is found from sea level up to 2,700 m but is most common at the lower end of its altitudinal range. Primarily terrestrial, P. gymnotis seeks refuge in dens, which are constructed in caves, under trees, and along stream beds. It may also be found in cultivated gardens, despite close proximity to humans. ("Ground Cuscus", 2004; George, 1987; Leary, et al., 2010; Majnep and Bulmer, 2007; Ramono and Nash, 1992)

Phalanger gymnotis has a short, coarse, grey-brown or silver-grey coat that contains a dark mid-dorsal stripe. Fur continues down the rump, covering the top of the tail. The remainder of the tail is covered in small bumpy growths that increase friction for gripping. Phalanger gymotis has little to no fur on the ears. The lack of fur on the ears and the dark dorsal stripe distinguish P. gymnotis from other members of its parent genus, Phalanger. At higher altitudes, tail fur is more dense and may have a white tip. Similar to other members of Phalanger, P. gymnotis has five digits on each foot, including a single opposable digit on the hind feet. The opposable digit is the only digit lacking a claw. Ground cuscuses vary in mass from 1,500 g to 4,850 g and in length from 310 mm to 539 mm. Tail length makes up a significant portion of its body length and ranges from 290 mm to 335 mm. Individuals in the northernmost part of its range tend to be larger, while individuals at higher altitudes are smaller than those a lower altitude. (Feiler, 1978; Flannery, 1995; Flannery, 2004; George, 1987; McNab, 2008)

The skulls of Phalanger gymnotis feature a powerful zygomatic arch and prominent sagittal crest, a narrow rostrum, and short paroccipital processes. Phalanger gymnotis is further divided into two subspecies, P. gymnotis gymnotis and P. gymnotis leucippus, which are differentiated by the wider palate and broader nasals of P. gymnotis gymnotis. The basal metabolic rate of P. gymnotis is 518.2 cm^3 oxygen/hour. Sexual dimorphism has not been reported in this species. (Feiler, 1978)

Little is known about breeding in Phalanger gymnotis in the wild. In captive populations, males court females by chasing and biting prospective mates when they are in estrus. Chasing may occur during daylight hours, but is most common at night, as Phalanger gymnotis is nocturnal. Although the mating system is unknown, it is either polygynous or polygynandrous, as males have been noted mating with at least two different females. (Shoemaker and Croxton, 1982)

Phalanger gymnotis mates year round and gives birth to a single newborn. Although gestation lasts 13 days, delayed implantation may occur, lengthening the time between copulation and birth. Females are almost always found to have a single young in their pouch, so the breeding interval is assumed to correspond with the length of time to independence for young. Young remain in the mothers pouch for approximately three months, at which point they exit the pouch at night. They continue to sleep in the pouch until the age of 5-7 months, when they leave permanently. Time to weaning is unclear as the continued use of the pouch makes weaning observations difficult. ("Ground Cuscus", 2004; Shoemaker and Croxton, 1982)

Young are altricial and remain in the mother's pouch, not leaving permanently until the age of 5-7 months. The mother provides milk, but time to weaning is unknown. Young exit the pouch first at night, at approximately 3 months old. The young do not exit during the day to sleep alone until the age of 4 to 5 months. (Flannery, 1995; Shoemaker and Croxton, 1982)

The lifespan of wild Phalanger gymnotis is unknown, but individuals at least 15 years of age have been recorded in captivity. (Flannery, 1995; Goodnight, et al., 2007)

Outside of mating season, Phalanger gymnotis is solitary and asocial, and individuals are often aggressive toward conspecifics. Fighting is common and includes hissing, honking, foot thumping and striking opponents with the forelimbs. Phalanger gymnotis constructs terrestrial dens and forages in the mid to lower canopy at night. It generally remains on low, stable branches while foraging. Using a flexible, gripping tail and opposable hind thumbs, P. gymotis is an accomplished climber and can easily traverse forest habitats. Phalanger gymnotis is almost entirely nocturnal, however, some individuals have been seen outside their dens during the early morning. ("Ground Cuscus", 2004; Flannery, 1995; Shoemaker and Croxton, 1982; Wilson and Reeder, 2005)

There is no information available regarding the home range of Phalanger gymnotis.

Phalanger gymnotis uses urine and cloacal gland secretions as scent markers. The scent, produced by both males and females, is said to smell like coffee. It likely uses pheromones to demarcate territorial boundaries and to attract potential mates. Ground cuscuses communicate vocally before and during mating and while fighting. While fighting, P. gymnotis hisses, honks, and foot thumps to communicate aggression. (Flannery, 1995; Shoemaker and Croxton, 1982)

Phalanger gymnotis is primarily frugivorous, but also consumes eggs, seeds, and leaves. It forages on the fruit and leaves of plants from numerous genera, including Elaeocarpus, Ficus, Pipturus, Pandanus, Oenathe, Rungia, and Ficus odoardii. Fruit is collected from trees and from the ground. Female ground cuscuses have been observed filling their pouches with fruit and then returning to their home dens where it is stored. (Flannery, 1995; Ganslosser and Etter-Ganslosser, 1990; Hume, et al., 1997; Mack and Wright, 2005; Wilson and Reeder, 2005)

Other than humans, Phalanger gymnotis has no documented predators. Humans prey upon P. gymnotis using traps, dogs, and traditional hunting methods. The nocturnal, solitary, and arboreal habits of P. gymnotis likely reduces risk of predation. (Leary, et al., 2010; Whitehead, 2000)

Fruit dispersion may be increased by Phalanger gymnotis. As large frugivores, ground cuscuses are one of the only species large enough to disperse virtually all fruits in the New Guinean rainforest. By translocating fruit and ingesting seeds, P. gymnotis is likely an important seed disperser throughout its geographic range. Parasites specific to this species have not been documented. (Mack and Wright, 2005; Shoemaker and Croxton, 1982)

Phalanger gymnotis is hunted for its meat year round and is an important protein source for rural populations throughout Papua New Guinea. In some communities, P. gymnotis is consumed only by senior elders of the community and is considered to have medicinal qualities. (Dwyer, 1982; Leary, et al., 2010; Whitehead, 2000)

Ground cuscuses may dwell in and around cultivated gardens and eat crops such as sweet potatoes. (Majnep and Bulmer, 2007; Ramono and Nash, 1992)

Although hunting has significantly reduced local populations of Phalanger gymnotis, the species remains widely distributed and is abundant throughout its geographic range. It is classified as a species of "least concern" on the IUCN's Red List of Threatened Species. In Indonesia, P. gymnotis is protected by law and cannot be captured, kept or traded. Until recently, it was acceptable for only the most senior members of many regional tribes in New Guinea to consume Phalanger gymnotis, and as a result, was infrequently hunted. As food taboos in rural villages changed during the 1970s and 1980s, P. gymnotis became an acceptable food source for members of almost all social levels resulting in increased pressure from hunting. ("Ground Cuscus", 2004; Flannery, 2004; Majnep and Bulmer, 2007; Ramono and Nash, 1992; Whitehead, 2000)

Phalanger gymnotis was formerly a member of the genus Spilocuscus, but molecular data led to its reclassification. It includes two subspecies, P. gymnotis gymnotis and P. gymnotis leucippus. (Feiler, 1978; Osborne and Christidis, 2002)