245.

Ernst Mayr’sWater Rat

Leptomys ernstmayri

French: Leptomys de Mayr / German: Ernst-MayrNeuguinea-Wasserratte / Spanish: Rata de agua de Ernst Mayr

Other common names: Ernst Mayr's Leptomys

Taxonomy. Leptomys ernstmayri Rimmler, 1932,

Ogeramnang, Saruwaged Mountains, 1785 m, Huon Peninsula, Morobe Province, NE (Papua) New Guinea.

Leptomys ernstmayri has been recognized as variously a full species, a subspecies of L. elegans and a synonym of L. elegans . It was defended as a full species in 2008 by G. G. Musser and colleagues. Current delineation of ernstmayri includes populations from four discrete montane areas in New Guinea, each population geographically isolated and morphologically differentiated in body proportions and craniodental morphology; each likely represents a discrete evolutionary lineage, and further taxonomic subdivision is probably warranted. Monotypic.

Distribution. Recorded from montane localities isolated by intervening areas of lowland habitat in New Guinea, including Foja Mts, Adelbert Range, Huon Peninsula (Finisterre and Saruwaged ranges), and E Central Cordillera, including both N (Jimi and Ramu rivers) and S catchments (Purari and Aroa rivers).

Descriptive notes. Head-body 124-156 mm, tail 132-171 mm, ear 15-24 mm, hindfoot 33-42 mm; weight 48-70 g. Leptomys species are unmistakable medium-sized terrestrial rats with short, dense, and silky or velvet-like 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 ears, which moderately large and thinly furred; upper surfaces of feet white, long and narrow hindfeet having 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. Ernst Mayr’s Water Rat, one of smaller members of genus, hasfur tawny brown on mid-back and flanks, fur of underparts, from chin to base oftail, with gray-based hairs tipped with white or pale buff; head lacks dark mask around eyes or pale spot on crown; tail is proportionally longer (93-122% of headbody length) than in most congeners. It differs from other Leptomys also indetails of cranial and dental morphology. Spermatozoal morphology features sperm headwith long apical hook and two shorter ventral hooks, long tail.

Habitat. All records of Ernst Mayr’s Water Rat are from localities within primary evergreen lower montane forests at elevations of 1150-2200 m. No confirmed records from secondary forest associations, although some from localities subject to regular visitation by hunters and subject to some degree of resource extraction.

Food and Feeding. H. M. Van Deusen reported capture of multiple specimens in 1964 in Rawlinson Range by a local man using a deadfall trap baited with live beetles. Stomach of one individual from Schrader Range (Jimi River catchment) contained arthropods (including termites, spiders, cockroaches, and chalcid beetles), as well as fungal hyphae. These details are consistent with observationsof dietary focus on insects for other species of Leptomys .

Breeding..ow mammary formula (two pairs) indicates small litter size. Each of two pregnant females carried a single fetus. There is one record of Ernst Mayr’s Water Rat occupying an underground nest in a burrow.

Activity patterns. No information.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Although this species is better represented than any other Leptomys, recent fieldwork has not found it to be anywhere abundant.

Bibliography. Breed & Aplin (1995), Ellerman (1941), Hide et al. (1984), Flannery (1995b), Helgen, Leary & Wright (2016i), Lidicker (1968, 1973), Lidicker & Brylski (1987),Menzies & Dennis (1979), Musser & Carleton (1993, 2005), Musser, Helgen & Lunde (2008), Riummler (1932, 1938), Tate (1951), Van Deusen (1966), Watts & Baverstock (1994a, 1996).