Phalanger gymnotis (Peters & Doria, 1875)

Russell A. Mittermeier & Don E. Wilson, 2015, Phalangeridae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 456-497 : 490

15.

Ground Cuscus

Phalanger gymnotis

French: Phalanger gymnote / German: Gleichfarbkuskus / Spanish: Cuscus terrestre

Other common names: Aru Island Ground Cuscus, Ground Phalanger

Taxonomy. Phalangista (Cuscus) gymnotis Peters & Doria, 1875 ,

“ Insulae Aru , prope Giabu-Lengan ” (= Gialnhegen Island, Aru Islands, Indonesia). Restricted by van der Feen in 1962 to “village on the west coast of Wokam I., Aru Is.”

This species has sometimes been placed in the genus Strigocuscus , but it belongs in the genus Phalanger . Two subspecies are sometimes recognized (nominate gymnotis , either considered restricted to the Aru Islands or to the Aru Islands plus lowland New Guinea, and leucippus named by O. Thomas in 1898, either considered to occur across New Guinea or to be restricted to the mountains of New Guinea), but the basis for subspecies recognition is not well documented and patterns of variation within this species require careful taxonomic attention. Monotypic.

Distribution. [Lowlands and mountains of New Guinea, also in various land-bridge islands off W New Guinea, including, Yapen, Salawati, Misool, and Aru Is.

Descriptive notes. Head—body 31-54 cm, tail 29-39.5 cm; weight 1.5-5 kg. The Ground Cuscus is a medium-sized or relatively large cuscus with a powerful body. Its pelage is gray to gray-brown dorsally, with dark dorsal stripe and pale ear flashes; coarsely tuberculated tail that lacks fur for one-half its length and often terminates in a white tip; and relatively small ears. Skull is medium to large (condylobasal length 74-96 mm) and robustly built, with narrow rostrum and wide zygomata. Secator (third upper premolar) is very large (proportionally larger than in any other phalangerid), set at an acute angle to molar row, and projects considerably higher than crowns of upper molars. Ground Cuscuses from montane forests at elevations above 1000-1500 m have considerably smaller bodies with longer and softer fur than those from lowland habitats.

Habitat. Forested habitats from sea level to elevations of ¢.2700 m but most commonly encountered at elevations of 500-1500 m.

Food and Feeding. The Ground Cuscus is primarily folivorous—frugivorous, but it also eats some animal matter. Plants reported in the diet include fruits of the genera Elaeocarpus (Elaeocarpaceae) , Ficus (Moraceae) , Garcinia (Clusiaceae) , Pipturus (Urticaceae) , and Pandanus (Pandanaceae) , and the herbs Oenanthe (Apiaceae) and Rungia (Acanthaceae) . Ferns (Pneumatopteris) are also apparently important in the diet, and it is known to eat a variety of other plant matter, including garden weeds ( Erechtites , Asteraceae ), sweet potato, and bananas. The Ground Cuscus reportedly feeds opportunistically on small vertebrates (rodents and lizards). Several observations suggest that females carry food in their pouches back to their dens.

Breeding. The Ground Cuscus produces one offspring at a time, with young recorded throughout much of the year (April-October), suggesting no distinct breeding season. When not in estrous, captive female Ground Cuscuses are often incompatible and fight with each other, which can result in severe lacerations. Individuals caught in the wild often have torn ears, facial scars, and missing digits, suggesting they frequently fight with each other. Observations of captive individuals suggest they leave the pouch at ¢.108 days old and stay out regularly at c.138 days old (when they may ride on the mother’s back), and remain permanently out of the pouch at 160-200 days old. Captive individuals are known to live for at least eleven years.

Activity patterns. The Ground Cuscus is nocturnal and rests by day in holes in the ground (dens or “lairs”) under tree roots, along steep banks of streams and rivers, among rocks and boulders, in thickets of vegetation, or in caves or manmade tunnels. They may occasionally sleep in hollow logs or hollows in trees situated low off the ground. Observations from hunters also suggest that Ground Cuscuses sun themselves outside their burrows in the early morning.

Movements, Home range and Social organization. Ground Cuscuses produce noises including hindfoot thumping, hissing, and repeated, noisy, cough-like honks. Both sexes are known to scent-mark by dribbling urine and producing a creamy-white secretion from cloacal glands. This secretion is produced as a stream as hips are swayed rhythmically from side to side, which leaves a curved line of scent on substrate. Observations of captive Ground Cuscuses indicate that they move in a slow deliberate manner and they can adopt an upright bipedal position when fighting, enabling them to strike out using their forelimbs.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Ground Cuscus has a wide distribution and large overall population, and it appears to tolerate a variety of habitats including degraded habitats. Although the Ground Cuscus 1s hunted and may be extirpated in some local areas, these impacts are not considered severe enough to warrant placing it in a threatened conservation category.

Bibliography. Bulmer & Menzies (1972), van der Feen (1962), Flannery (1995a, 1995b), George (1982, 1987), Hume et al. (1997), Leary, Singadan, Menzies, Helgen, Wright, Allison, Salas & Dickman (2008b), Majnep & Bulmer (2007), Menzies (1991), Menzies & Pernetta (1986), Thomas (1898b), Wemmer & Collins (1977).

Figures

11. Peleng Cuscus (Phalanger pelengensus), 12. Moluccan Cuscus (Phalanger ornatus), 13. Gebe Cuscus (Phalanger alexandrae), 14. Obi Cuscus (Phalanger rothschildi), 15. Ground Cuscus (Phalanger gymnotis), 16. Woodlark Cuscus (Phalanger lullulae), 17. Northern Common Cuscus (Phalanger orientalis), 18. Eastern Common Cuscus (Phalanger intercastellanus), 19. Southern Common Cuscus (Phalanger mimicus), 20. Telefomin Cuscus (Phalanger matanim), 21. Stein’s Cuscus (Phalanger vestitus), 22. Silky Cuscus (Phalanger sericeus), 23. Mountain Cuscus (Phalanger carmelitae), 24. Black Spotted Cuscus (Spilocuscus rufoniger), 25. Waigeo Spotted Cuscus (Spilocuscus papuensis), 26. Admiralty Spotted Cuscus (Spilocuscus kraemeri), 27. Blue-eyed Spotted Cuscus (Spilocuscus wilsoni), 28. Common Spotted Cuscus (Spilocuscus maculatus), 29. Australian Spotted Cuscus (Spilocuscus nudicaudatus)

Distribution. [Lowlands and mountains of New Guinea, also in various land-bridge islands off W New Guinea, including, Yapen, Salawati, Misool, and Aru Is.