Hypsiprymnodon moschatus, Ramsay, 1876

Russell A. Mittermeier & Don E. Wilson, 2015, Hypsiprymnodontidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 592-599 : 599

Musky Rat Kangaroo

Hypsiprymnodon moschatus

French: Bettong musquée / German: Moschusrattenkanguru / Spanish: Rata canguro almizclena

Other common names: Hypsi, Musky Rat-kangaroo

Taxonomy. Hypsiprymnodon moschatus Ramsay, 1876 ,

“ Rockingham Bay district ,” Queensland, Australia.

This species is monotypic.

Distribution. NE Australia, restricted to NE Queensland, from Helenvale (Mt Amos) W to Ravenshoe, and S to about Ingham.

Descriptive notes. Head-body 15-27 cm, tail 12-16 cm; weight 360-680 g. Musky Rat Kangaroos are not sexually size dimorphic, and although their hindlimbs are larger than forelimbs, difference is much less than in other kangaroos, wallabies, and their relatives. Fur is rich rufous-brown over body with very dark-brown guard hairs dorso-laterally but absent from belly. Some Musky Rat Kangaroos have a cream or white patch on ventral surface of throat or chest. Head has shorter, softer fur that becomes grizzled and gray when an individual ages; head of a subadult is similar in color to body. Tail, hands, and feet of Musky Rat Kangaroos appear naked and covered with shiny scale-patterned skin, but scale patterning is interspersed with sparse short hairs. Head is long and slender with no concavity in its profile. Prominent eyes are central and lateral in the skull. Manus and pes have five digits; the Musky Rat Kangaroo is the only member of the suborder Macropodiformes to have five digits on pes. Second and third digits are syndactyl (fused). Female pouch contains four mammae.

Habitat. Wet tropical, closed-canopy rainforests from sea level to elevations above 1200 m. Distribution of the Musky Rat Kangaroos in these rainforests is quite broad, but they do not traverse non-rainforest habitats and do not occur in rainforest remnants less than c.440 ha. They reach their highest densities in wettest rainforest types on richest soils, particularly basalt soils. Musky Rat Kangaroos also occur at lower densities on granite soils that are common on forested ranges within their distribution, and their populations are prone to appear and disappear at higher elevations.

Food and Feeding. Musky Rat Kangaroos feed primarily on pericarps offruits from a wide variety of rainforest trees, shrubs, and vines. They also eat seeds, invertebrates, and fungi. Musky Rat Kangaroos also rarely eat flowers (e.g. Austrobaileya scandens , Austrobaileyaceae ), leaftissue (e.g. Liliaceae ), and cambium of some trees. Musky Rat Kangaroos show a preference for large fruits with thick flesh and seeds with a relatively soft seed coat. Their diet varies seasonally with changes in availabilities offruits and seeds, invertebrates, and fungi. Fruits dominate diets of Musky Rat Kangaroos throughout the year but peak in October—January in most years. Invertebrates are eaten most often in May-July and fungi in the wet season in February-April. During the season when fruit availability is low, adults may lose more than 20% of their body weight.

Breeding. Musky Rat Kangaroos regularly give birth to twins, occasionally triplets and rarely single young or quadruplets; all other macropodiforms give birth to single young. Reproduction of the Musky Rat Kangaroo is seasonal reflecting the seasonal cycle of fruit production. Testes size increases fourfold in September-October, coincident with a seasonal increase in fruit availability. This seasonal enlargement oftestes could be the only time that males are reproductive, or it may be due to increased sperm competition among males when most females go into estrus. Births, growth rates, and pouch eviction of young are loosely synchronous with births occurring over only three months in February-April. Gestation is 19 days, and young remain in the pouch for 21 weeks. After being evicted from the pouch, young remain in a nest to be periodically visited and suckled by the mother. Mothers and young forage together for a short time in October before young forage independently from November on (at c.150 g), although they are still fed on milk. Young are fully weaned by January at c.300 g. Females probably go into estrus immediately after weaning their young. They can reproduce at 20 months and may breed over 2-3 seasons. Although still uncertain, it is likely their life span does not go much beyond 4-5 years.

Activity patterns. Musky Rat Kangaroos are strictly diurnal, sheltering in well-built leaf nests at night and sometimes through the middle of the day. Most activity occurs through the early to mid-morning and from late afternoon to dusk, although they may be seen foraging at any time throughout the day. During heavy rain, not uncommon in their habitat, they often retire to their leaf nest or other shelters such as among the flying buttress roots of the large rainforest tree known as gray satinash or watergum ( Syzygium gustavioides , Myrtaceae ).

Movements, Home range and Social organization. Musky Rat Kangaroos are solitary and promiscuous occupying overlapping home ranges from under 1 ha to more than 4 ha. Adults are almost never seen socializing except on rare occasions that a few individuals tolerate one another at a collection of fallen fruit. Musky Rat Kangaroos move constantly and frequently follow regular pathways defined by cable roots and trunks of fallen trees and branches. In this way, they generally use their entire home range during each day of foraging. They also climb into crowns offallen trees and low vine tangles but rarely climb more than 2 m of the ground. During the breeding season, male Musky Rat Kangaroos may engage in chases where a dominant individual quickly displaces a subordinate and may strike out with a forepaw at the rump of a fleeing combatant. Occasionally, individuals may alternate between chasing and being chased. Males are extremely violent toward each other in captivity when in the presence of a female.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Australia’s Environmental Protection and Biodiversity Conservation Act and the Nature Conservation Act of Queensland, their home state, also considers the Musky Rat Kangaroo to be of least concern. Most habitats are now protected in national parks such as Crater Lakes, Wooroonooran, or Girrungun, and the Wet Tropics of Queensland World Heritage Site. There is no evidence of any significant or ongoing declines of populations of the Musky Rat Kangaroo; however, there are indications of possible contractions in its distribution at some locations.

Bibliography. Bates et al. (2014), Bennett & Baxter (1989), Claridge et al. (2007), Dawson (1989), Dennis (1997, 2002, 2003), Dennis & Johnson (2008a), Dennis & Marsh (1997), Dennis & Westcott (2006, 2007), Dennis et al. (2005), Heighway (1939), Hume (1982), Johnson & Strahan (1982), Johnson et al. (1983), Lloyd (2001), Owen (1877 1878, 1879), Ramsay (1876b), Schirer (1985), Seebeck et al. (1989), Vernes et al. (2001), Woods (1960).

Figures

Musky Rat Kangaroo

Distribution. NE Australia, restricted to NE Queensland, from Helenvale (Mt Amos) W to Ravenshoe, and S to about Ingham.