247.

Fly River Water Rat

Leptomys signatus

French: Leptomys a front blanc / German: Fly-Neuguinea-\ Wasserratte / Spanish: Rata de agua de Fly

Other common names: Fly River Leptomys

Taxonomy. Leptomys signatus Tate & Archbold, 1938,

“Sturt Island Camp, Fly River (n. bank), near Fairfax Islands, Western Division, Papua [New Guinea]; sea level.”

Leptomys signatus has usually been treated as a subspecies of L. elegans, but since 2005 has been regarded as a full species follow-ing assessment by G. G.Musser and M. D. Carleton. Monotypic.

Distribution. Known only from a few localities in SC New Guinea, including upper and lower Fly River and middle Strickland River catchments, Mt Bosavi, and Darai Plateau.

Descriptive notes. Head—body 140-155 mm, tail 143-155 mm, ear 19-21-5 mm, hindfoot 36-45 mm; weight 80 g. Leptomys species are unmistakable medium-sized terrestrial rats with short, dense, and silky or velvetlike fur, buff gray to orange brown on upperparts, cream or white below; black-tipped guard hairs barely project through general pelage; head with long, slender snout, and long vibrissae extending well past 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 is slender, finely scaled, and 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. Two mammae on each side, both inguinal. The Fly River Water Rat, a medium-sized member of genus, has fur on upperparts shorter (8 mm) than that of congeners, dense and velvety, grayish brown on back and flanks; fur of underparts pure white from chin to base oftail; head lacks dark mask around eyes but has conspicuous white/pale tan spot on crown; hindfeet are proportionally longer and broader than in other Leptomys . Tail is moderately long (92-111% of head-body length), with distal one-third to half white above and below. It differ from other Leptomys also in details of cranial and dental morphology.

Habitat. Habitat at the Sturt Island camp was evergreen lowland forest growing on lateritic ridges, with swamp forest of Melaleuca (Myrtaceae) and sago palms ( Metroxylon, Arecaceae) in low-lying areas, and with groves of bamboo in which specimens were trapped. The Darai Plateau is rugged limestone karst supporting floristically highly diverse evergreen hill forest communities. Other recent records in upper Fly and middle Strickland river catchments are from primary evergreen hill forest, mostly growing on uplifted alluvium. At 1500 m on Mount Bosavi theFly River Water Rat would occupy evergreen lower montane rainforest; occurrence at such high elevation on Bosavi may be due to absence of other Leptomys on this isolated volcanic peak. Mount Sisa, to immediate north of Mount Bosavi, supports a population at equivalent elevation. The Fly River Water Rat is not found in the well-surveyed Purari River catchment to the east of Kikori River.

Food and Feeding. No information.

Breeding..ow mammary formula (two pairs) indicates small litter size. A pregnant female captured on Darai Plateau had a single embryo.

Activity patterns. Camera-trapping records of this species suggest that it is active exclusively at night.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Fly River Water Rat appears to be nowhere particularly abundant.

Bibliography. Ellerman (1941), Flannery (1995b), Helgen & Oliver (2004), Leary (2004, 2016), Menzies & Dennis (1979), Musser & Carleton (1993, 2005), Musser, Helgen & Lunde (2008), Tate (1951), Tate & Archbold (1938).