246.

Small Water Rat

Leptomys paulus

French: Leptomys nain / German: Kleine Neuguinea-Wasserratte / Spanish: Rata de agua pequena

Other common names: Small Leptomys

Taxonomy. Leptomys paulus Musser, K. M. Helgen & Lunde, 2008,

“Number 2 Camp, N slopes Mount Dayman, Manaeu Range, 1370 m asl, Milne Bay Province, Papua New Guinea.”

Examples of L. paulus were previously reported as belonging to L. elegans or L. ernstmayri . Monotypic.

Distribution. Known only from three localities on SE Papuan Peninsula of New Guinea (Astrolabe and Maneau ranges).

Descriptive notes. Head-body 117-132 mm, tail 138-163 mm, ear 18-23 mm, hindfoot 31-36 mm; weight 34-52 g. Species of Leptomys are unmistakable medium-sized terrestrial rats with short, dense, and silky or velvet-like fur, buff gray to orange brown on upperparts, cream or whitebelow; black-tipped guard hairs barely project through general pelage; head with long, slender snout and long vibrissae that extend well past the moderately large, thinly furred ears; upper surfaces of all feet white, long and narrow hindfeet having all digits with claws, plantar pads relatively small; tail slender, finely scaled, with three short hairs per scale, basal portion dark above and white or mottled below, distal portion entirely white, no terminal brush or prehensile pad. Cranium is relatively narrow and delicate, with fairly robust upper incisors bearing orange enamel and forward-projecting lower incisors with paler yellow enamel; three molars, initially cuspidate but basined when worn, posterior molars very reduced. Mammae two on each side, both inguinal. The Small Water Rat, the smallest member of genus, has the fur on upperparts longer (up to 12 mm) than that of congeners and soft and silky, tawny brown on mid-back and flanks; fur of underparts is variable, some with gray-based hairs tipped with white or pale buff, some with pure white patch on chest only, some pure white over entire underside. Head lacks dark mask around eyes and pale spot on crown, but has short, dark hairs on vibrissal pads. Tail is proportionally longer (108-128% of head-body length) than that of most other members of genus, with distal quarter white above and below. It differs from other Leptomys also in details of cranial and dental morphology.

Habitat. All capture records are from sites in evergreen tropical lower montane rainforest, at elevations of 1240-1525 m. Lower-elevation sites in hill forest on Mount Dayman produced captures of Elegant Water Rat ( L. elegans);Owen Stanley Range has produced records of Elegant Water Rats at lower elevation and of Ernst Mayr’s Water Rats ( L. ernstmayri) at higher elevations than the single record of Small Water Rat at 1500 m.

Food and Feeding. Specimens have been collected in snap traps baited with beetle larvae.

Breeding. The low mammary formula (two pairs) indicates small litter size. Two pregnant females captured in 1997 carried one and two uterine embryos, respectively. The Small Water Rat has been excavated from burrows that contained a single nest chamber about 1 m below ground surface.

Activity patterns. No information.

Movements, Home range and Social organization. Excavated nests of Small Water Rats usually contained single individual adults or an adult female with one or more juveniles. One nest was reported as containing an adult male, two subadult males, and two subadult females.

Status and Conservation. Not assessed on The IUCN Red List. This species appears to be moderately abundant in the lower montane forests of the Maneau Range. The single occurrence at Kagi in Central Province is perplexing given theamount of historical trapping effort in this region of Papua New Guinea.

Bibliography. Cole et al. (1997), Flannery (1995b), Musser & Carleton (1993, 2005), Musser, Helgen & Lunde (2008).