332.

False Water Rat

Xeromys myoides

French: Rat des mangroves / German: Falsche Schwimmratte / Spanish: Raton de agua

Other common names: False Swamp Rat, Water Mouse

Taxonomy. Xeromys myoides Thomas, 1889,

Port Mackay, Queensland, Australia.

Xeromys has been found to be sister to Pseudohydromys, although further genetic research is needed. Although no subspecies of X. myoides have been described, there is substantial morphological variation across this species’ range for which taxonomic implications have not yet been resolved. Monotypic.

Distribution. Highly fragmented around coastal N & E Australia from the Daly River in NW Northern Territory to SE Queensland, including Melville I, Fraser I, Bribie I, North Stradbroke I and South Stradbroke I; few records also in S New Guinea.

Descriptive notes. Head-body 72-130 mm, tail 62-100 mm, ear 10-15 mm, hindfoot 23-26 mm; weight 32-64 g. The False Water Ratis a distinctive species of rat with small eyes and short, dense, and silky fur. Dorsal pelage is lustrous and ranges in color from slate gray to grayish brown, generally being a little darker along the middle of the back. On Stradbroke Island, they usually have white specks on the dorsal pelage. Ventral pelage is pure white and sharply demarcated from dorsal pelage. Ears are small and rounded, being well furred and silvery gray near the ends and pink internally. Vibrissae are relatively long. Feet are white and nearly naked; hindfeet are elongated. Forefeet with five pads and hindfeet with six pads. Pollex with a short, broad nail instead of a claw is in the other four digits. Tail is shorter (¢.80%) than head-body length, thinly covered in short white hairs, smooth, and pale whitish in color. The species is known to have a strong, pungent musty smell. Skull with two molars in each of the upper and lower rows, a smoothly convex interorbital region, a short anterior palatine foramin, long incisors, and longer nasals than in Hydromys . Diploid number 2n = 48; FN = 52.

Habitat. Restricted to freshwater and saline wetlands, mangroves, and floodplain grasslands and sedgelands.

Food and Feeding. The False Water Rat forages on the ground, in tidal flats, and around water’s edge (often following receding tide in mangrove habitats). Its diet consists mostly of invertebrates, including crabs, pulmonates, and mollusks. It often consumes its prey in sheltered areas such as hollow logs, and may leave “middens” of prey remnants at favored feeding sites.

Breeding. Reproduction occurs all year-round, and litter size is 1-4.

Activity patterns. Terrestrial and nocturnal. The False Water Rat is semi-aquatic, although it rarely swims. It uses mud to construct amound up to at least 60 cm tall, in which it creates a maze of tunnels, including a nesting chamber. These mounds are used for shelter during day, and sometimes at night when high tides inundate surrounding area. In some situations,it shelters in burrows established in natural earth banks, or mud structures around hollow tree trunks.

Movements, Home range and Social organization. False Water Rats are sedentary, but radio-tracking studies have reported individuals traveling nearly 3 km per night, often along well-used pathways; home range size 0-6 ha in one study and 3-4 ha in another. Mound nests may hold up to eight occupants, but typically with one adult male, more than one adult female, and subadults and juveniles.

Status and Conservation. CITES Appendix I. Classified as Vulnerable on The IUCN Red List. The False Water Ratis listed as vulnerable under Australian legislation. Large parts of its range have suffered habitat degradation through coastal development, inundation associated with global climate change, and impacts of livestock and feral animals; it is also subject to predation by feral pigs and feral cats.

Bibliography. Ball (2004), Gynther (2011), Hitchcock (1998), Magnusson et al. (1976), Redhead & McKean (1975), Russell & Hale (2009), Traill et al. (2011), Van Dyck (1997), Van Dyck & Gynther (2003), Van Dyck & Strahan (2008), Watts & Aslin (1981), Woinarski, Brennan etal. (2000), Woinarski, Burbidge & Harrison (2014).