279.

Northern Groove-toothed Shrew Mouse

Microhydromys richardsoni

French: Hydromys de Richardson / German: Nordliche Kleinwassermaus / Spanish: Raton musarana de dientes estriados septentrional

Other common names: Richardson's Shrew Mouse

Taxonomy. Microhydromys richardsoni Tate & Archbold, 1941,

“4 kilometers SW. of Bernhard Camp, Idenburg River, Netherlands [= Papua] New Guinea, altitude 850 meters.”

Microhydromys richardson: until recently included M. argenteus . Monotypic.

Distribution. Known only from a few localities in N catchments of Central Cordillera of New Guinea.

Descriptive notes. Head-body 79-83 mm, tail 84-92 mm, ear 8-12 mm, hindfoot 17-20 mm; weight 11 g. Species of Microhydromys are tiny murines with short, velvety fur gray to brown on upperparts and slightly paler below; head with very reduced eyes, long, fine vibrissae, and moderately large ears; all feet with claws on all digits, hindfeet narrow and with small plantar pads; tail approximately equal to combined

length of head and body, thinly furred, all dark or with short white tip. Cranium with short rostrum, proportionally small molars, and proportionally large auditory bullae. Dentition characterized by longitudinally grooved upper incisors, loss of third molars, and basined molar morphology. Distinguishing features of the Northern Groove-toothed Shrew Mouse are tail slightly longer than head-body length and dark for entire length; upperparts paler gray brown and venter only slightly paler; hindfeet slightly longer and clothed in white hairs; ears slightly smaller and darker. Mammae two on each side, both inguinal.

Habitat. Forest, at elevations of 20-1500 m. The four known localities are in contrasting habitats: low-elevation hill forest on limestone karst in the Oenake Range; midelevation hill forest on metamorphic basement at Frieda River, and higher-elevation mossy hill forest with montane elements (species of Nothofagus, Nothofagaceae; and Agathis, Araucariaceae) at Idenburg River; “secondary forest” at Wanuma; and unspecified habitat but within aregional mosaic of lower montane forest and secondary forests generated by shifting agriculture in Telefomin Valley.

Food and Feeding. No information.

Breeding. [.ow mammary formula (two pairs) indicates a small litter size.

Activity patterns. Body proportions indicate terrestrial lifestyle, while somber coloration and small eyes suggest nocturnal and possibly semi-fossorial lifestyle.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Data Deficient on The IUCN Red List. Despite its considerable elevational range, the Northern Groove-toothed Shrew Mouse appears to be nowhere common and its distribution may be fragmented. Camera-trapping surveys at sites within its known range have repeatedy failed to obtain images of this species, and its remains were rarely found in the large owl pellet collection from Paleflatu Cave.

Bibliography. Archbold et al. (1942), Flannery (1989, 1995b), Flannery & Seri (1990), Gerrie & Kennerley (20161), Helgen & Helgen (2009), Helgen et al. (2010), Jackson & Woolley (1993), Musser & Carleton (2005), Tate (1951), Tate & Archbold (1941).