243.

Arfak Water Rat

Leptomys arfakensis

French

: Leptomys des Arfak / German: Arfak-Neuguinea-Wasserratte / Spanish: Rata de agua de Arfak

Other

common

names

: Arfak

Leptomys

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

“Arfak Mountains of the Vogelkop [= Bird’s Head] Peninsula of western New Guinea (Papua Province, Indonesia) at an altitude of 1000 m.”

The earliest report on the specimens of L. arfakensis, by G. Dollman in 1930, referred them to “ Melomys levipes ” (= Paramelomys levipes). Subsequent mentions prior to 2008 aligned them with either L. ernstmayri or L. elegans when Leptomys was regarded as a monotypic genus. Monotypic.

Distribution. Known only from two specimens collected in 1925 in the Arfak Mts, NW New Guinea.

Descriptive notes. Head-body 138-151 mm, tail 146 mm, ear 21 mm, hindfoot 36— 39 mm. No data are available for body weight. Leptomys species are unmistakable mediums-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 that extend well past ears; ears moderately large, thinly furred; upper surfaces of feet white, hindfeet long and narrow, all digits with claws, plantar pads relatively small; tail 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 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 Arfak Water Rat is a medium-sized member of genus; fur on upperparts moderately long (8-10 mm), dark brown on mid-back and buffy brown on flanks; underparts pure white from chin to base oftail; head with dark masks around eyes but lacking dorsal white blaze; tail equal (97-106%) to head-body length. Differs from the otherwise similar Elegant Water Rat ( L. elegans) in details of cranial and dental morphology and presence of well-developed hypothenar pad.

Habitat. General vegetation cover of Arfak Mountains is tropical evergreen rainforest; the capture locality at 1000 m lies close to the transition between hill forest and lower montane forest.

Food and Feeding. No information.

Breeding. [Low mammary formula (two pairs) indicates a smalllittersize.

Activity patterns. No information.

Movements, Home range and Social organization. No information.

Status and Conservation. Not assessed on The IUCN Red List. The Arfak Water Ratis not represented in Late Quaternary subfossil assemblages from the Ayamaru Plateau, lowland karst region to the west of Arfak Mountains. Given this, it is likely that the species is restricted to montane habitats on Bomberai Peninsula. The Arfak Mountains peak at 2955 m. No reports since initial description, but Arfak Mountains are without intensive mammal survey. Extensive forestry activity has had some impact on lowerelevation forests on Doberai Peninsula, but montane habitats remain largely intact. The southern part of Arfak Mountains, including its highest peak,falls within the Pegunungan Arfak Nature Reserve.

Bibliography. Dollman (1930), Laurie & Hill (1954), Mahoney (1968), Musser & Carleton (1993, 2005), Musser, Helgen & Lunde (2008), Pasveer & Aplin (1998), Rummler (1938), Tate (1951).