793.

Mamasa Water Rat

Waiomys mamasae

French: Rat de Mamasa / German: \Wasser-Spitzmausratte / Spanish: Rata de agua de Mamasa

Other common names: Mamasa Rat

Taxonomy. Waiomys mamasae Rowe, Achmadi & Esselstyn, 2014,

“Mount Gan- dangdewata (2-882898°S, 119-386448°E, 1571 m), Rantepangko, Mamasa, Sulawesi Barat, Indonesia.”

Waiomys is sister to Gracilimus, and that clade is sister to Sommeromys, which is then part sister to the Paucidentomys + Echio- thrix and Tateomys + Melasmothrix clades. Waiomys mamasae is the only species in the Sulawesi shrew and water rat clade that 1s semi-aquatic. Monotypic.

Distribution. Known only from a single specimen collected at type locality in WC Sulawesi.

Descriptive notes. Head-body 129 mm, tail 159 mm, ear 11 mm, hindfoot 36 mm; weight 64 g. The Mamasa Water Rat is a small semi-aquatic, broad snouted endemic rat of Sulawesi, being the only semi-aquatic rat on the island. Pelage is soft, fine, and extremely dense. Dorsum is gray-brown, with hairs having gray bases and light brown tips and sparsely distributed gray guard hairs. Dorsal fur extends to fingers of forefeet and ankles of hindfeet. Venter has hairs with much grayer bases and lighter gray tips, causing it to appear grayish white. Ventral pelage extends beyond upper lip and almost up sides and dorsal sides of limbs. Dorsal and ventral pelage cover base oftail; some ventral pelage extends outward up thighs, forming two conspicuous white spots on mid-thighs. Eyes are small and almost indistinguishable from pelage on head; ears are short, heavily furred, gray, and barely noticeable. Vibrissae are mostly short but some are fairly long, and they are dense and stiff, with black bases and unpigmented tips and shafts. Tail is ¢.125% of head-body length and ventrally covered by a line ofstiff white vibrissae that makeit look vertically flattened even though itis not; dorsal part of tail is gray-brown. Hindfeet are long and flattened like paddles with typical dark claws; forefeet are small, with nail pollex fused to side of palm. Skull is small, with few prominent ridges, and rostrum is moderate in length.

Habitat. Type specimen caught by hand in slow-moving and shallow high-mountain stream surrounded by dense montane tropical rainforest.

Food and Feeding. Stomach of the only specimen of the Mamasa Water Rat had larvae of Simulidae (black flies) and Hydropsychidae (net-spinning caddisflies), suggesting that it dives for food.

Breeding. No information.

Activity patterns. The Mamasa Water Rat is semi-aquatic and might be nocturnal.

Movements, Home range and Social organization. No information.

Status and Conservation. Not assessed on The IUCN Red List. The Mamasa Water Rat is apparently uncommon to locals in the area and could potentially be threatened by habitat destruction. More research is needed to fully understand its natural history and conservation threats.

Bibliography. Esselstyn et al. (2015), Rowe et al. (2014, 2016a, 2016b).