324.

White-tailed Giant Rat

Uromys caudimaculatus

French: Uromys a queue nue / German: WeiRschwanz-Riesenratte / Spanish: Rata gigante de cola blanca

Other common names: Atherton Uromys, Cape York Uromys, Giant Mosaic-tailed Rat, Giant Naked-tailed Rat, Giant White-tailed Rat, Giant White-tailed Uromys, Mottled-tailed Giant Rat, White-tailed Giant Uromys, White-tailed Uromys; Hinchinbrook Island Uromys (caudimaculatus).

Taxonomy. Hapalotis caudimaculata Krefft, 1867,

Cape York, Queensland, Australia.

Uromys has been found to be sister to a clade including Melomys, Solomys, and Paramelomys, as well as an undescribed taxon that may represent a separate genus that is indistinguishable from Melomys cervinpes. Within Uromys, U. caudimaculata is placed under subgenus Uromys along with U. anak, U. boeadu, U. emmae, U. hadrourus, and U. neobritannicus; it is most closely re-lated morphologically and phylogenetically to U. emmae, U. boeadii, and U. hadrourus . There are two discernible chromosomal races in Australia corresponding to the two populations in Queensland, which may warrant species recognition in further studies (under the names U. caudimaculatus and U. sherrini), although they are able to interbreed. Other populations of U. caudimaculatus should also be re-evaluated as there is substantial morphological variation throughoutits range, probably representing a species complex. Although the taxon aruensis has been regularly included as a subspecies, it is viewed here as a synonym of caudimaculatus until further revisions are made. Three subspecies recognized.

Subspecies and Distribution.

U.c.caudimaculatusKrefft,1867—SNewGuinea,AruIs,andN&NEQueensland,Australia,includingHinchinbrookI.

U. c. multiplicatusJentink, 1907 — W New Guinea and Waigeo I. U. c. papuanus Ramsay, 1883 — E New Guinea. Known also from Yapen I, off NW New Guinea, and Fergusson and Normanby Is (D’Entrecasteaux Is), but subspecies involved is not known.

Descriptive notes. Head-body 204-382 mm, tail 206-362 mm, ear 20-40 mm, hindfoot 34-80 mm; weight 400-900 g. The White-tailed Giant Rat is a large Uromys with proportionally long hindfeet. Pelage is relatively short and coarse, with longer dark guard hairs. Dorsal pelage is medium to dark grayish brown or tawny, and may be grizzled because of redor yellow-tipped hairs; it ismore gray on the sides, with a clear line of demarcation from ventral pelage, which is creamy white oryellow. Feet range from white (sometimes with a patch or line of brown) to buffy or brown, and are proportionally long and slender compared with those of congeners. Ears are short, rounded, and naked, and are grayish in color; vibrissae are long and black. Tail is relatively long (c.95-135% of head-body length), naked, and variably colored grayish black basally and white distally with extreme to no mottling during the transition; some individuals have tail yellow ventrally at base, not extending past basal third of tail. Skull has narrower rostrum than in Emma’s Giant Rat ( U. emmae) and less inflated braincase than the Masked White-tailed Giant Rat ( U. hadrourus). There are two pairs of mammae, both inguinal. Subspecies caudimaculatus is largest subspecies and has with shorter hindfeet then papuanus, feet being white with a brown line or patch above and yellow or white underparts; multiplicatus is smallest subspecies, with shorter hindfeet than caudimaculatus, has minimal to no mottling on tail, which is yellow ventrally for basal third and has grizzled fur; papuanus is between the two others in size, has longer (110-135%) tail that has extreme mottling with more white than black, creamy underside with gray smudges, and longer brown or buffy feet. The nematode genera Odilia and Macrostrongylus and various species of mite (including Laelaps) have been recorded from this species. Chromosomal complement is 2n = 46 (Australian populations) or 2n = 48 (New Guinea populations) and fundamental number is FN = 52 (Australian populations) or FN = 56 (New Guinea populations).

Habitat. Occurs in a variety of wooded areas, including primary and secondary tropical moist forest, closed sclerophyll forest, wet open woodland, swamps, and mangroves. It can be found in more open areas, such as wet open woodlands, melaleuca forests, swamps and mangroves, in lowland regions. In New Guinea, it is abundant in lowland and mid-montane regions. White-tailed Giant Rats occur at elevations from sea level to 1925 m.

Food and Feeding. The White-tailed Giant Ratis a generalist omnivore. In Australia its diet varies seasonally,and includes fruits, nuts, fungi, insects, small reptiles, amphibians, crustaceans, and bird eggs, as well as bark. Its strong jaws allow it to break into hard-shelled fruits, giving it an adaptive advantage over other rodent species (except the Masked White-tailed Giant Rat). In Atherton Tableland, hard-shelled seeds taken include those of, among others, yellow walnut ( Beilschmiedia bancroftii, Lauraceae), cream silky oak ( Athertonia diversifolia, Proteaceae), and hairy walnut ( Endiandra insignis, Lauraceae). Seeds are eaten on the spot, taken to a buttress or fallen log (where chewed seeds may be found in a midden), or cached up to 60 m from parent tree; buried seeds are usually covered by a few leaves, occasionally weighed down with a stick. In order to find large passalid beetles the rats tear through rotting logs and branches, and bark is a primary food source forthis species at certain times of the year. [tis known to feed also on mud crabs and other small crabs in mangroves, even foraging during daylight to find them. In New Guinea, White-tailed Giant Rats may feed on fruits of Pangium edule ( Achariaceae) and Pandanus (Pandanaceae), and can be a pest in coconut plantations as they are able to open youngcoconuts.

Breeding. In Australia, breeding generally starts in September/October, peaking at height of wet season in December/January, independent young generally common by March. Males become significantly more aggressive during height of breeding season. Gestation lasts 36 days, and young are born small and helpless;litter size is 2-3, rarely four. Young are rarely carried but, when they are, they are attached to the teat and mayfall off, this usually happening only when the animal is disturbed or endangered. Juveniles stay with the female for around three months andbecome independent at 250-300 g. The White-tailed Giant Rat is relatively long-lived, reaching at least four years regularly in the wild. Reproductive behavior of this species in New Guinea is relatively unknown, but a 200g semi-independent young was caught in late July in Torricelli Mountains and a 110g young was caught with its mother in June on Mount Karimui;litter size has been recorded as 1-3 in New Guinea during November—December, and young stay with their mother until they are half-grown.

Activity patterns. The White-tailed Giant Rat is nocturnal, resting in burrows or tree hollows during the day, although it isknown to hunt crabs in daylight in mangrove swamps. A recent study showed that it avoided predatory odors year-round, whereas some other rodents in the area avoided the odors only during certain times of the year. The species is both terrestrial and scansorial/arboreal. It is a very strong, agile, and capable climber that usesits forelimbs to grip while thrusting up large logs with its powerful hindlegs. Nests are made in underground burrows and in tree hollows in Australia and New Guinea, and probably also in caves in New Guinea; these rats have been recorded also in mine tunnels in New Guinea, where they raise their young on the bare rock. Tree-hollow nests are comparatively conspicuous, since claw marks draw attention to them; White-tailed Giant Rat nests are generally within 10 m of the ground and have narrow slit-shaped entrances. Burrows are found under various debris, including logs and fallen trees, as well as inundercut banks of streams and dry gullies.

Movements, Home range and Social organization. White-tailed Giant Rats are generally solitary; females with young and single individuals are usually found in their nests. Home ranges must be large for the rats to be able to move to find fruiting trees; the animals generally forage extensively in an area of at least 4 ha, and often well beyond that. Overnight movement of 500 m has been observed, and home ranges of individuals overlap extensively with those of their neighbors in complex patterns. There seems to be a large amount ofterritorial aggression.

Status and Conservation. Classified as Least Concern on The IUCN Red List. There are currently no major threats to the species and it has a wide distribution that encompasses many protected areas. The White-tailed Giant Rat is found in a variety of habitats and can survive in forest fragments as small as 7-5 ha, but it will not move between them if they are surrounded by agricultural land, which may lead to fragmentation as areas become more agriculturally developed. It is probably also preyed on by nonnative predators such as feral cats and by Dingos (Canis lupus dingo). The incisors of White-tailed Giant Rats are used as engraving tools throughout New Guinea.

Bibliography. Aplin et al. (2017), Baverstock, Gelder & Jahnke (1982), Baverstock, Watts & Hogarth (1976), Bryant et al. (2011), Comport & Hume (1998), Domrow (1962), Flannery (1995a, 1995b), Groves & Flannery (1994), Harrison (1962), Hayes et al. (2006), Menkhorst & Knight (2010), Moore (2010), Musser & Carleton (2005), Smales (2008), Steppan & Schenk (2017), Theimer (2001), Van Dyck & Strahan (2008), Wellesley-Whitehouse (1981).