240.

Ziegler’s Water Rat

Hydromys ziegleri

French: Hydromys de Ziegler / German: Ziegler-Schwimmratte / Spanish: Rata de agua de Ziegler

Other common names: Ziegler's Hydromys

Taxonomy. Hydromys ziegleri K. M. Helgen, 2005,

“Bainyik (03°40’S, 143°05°E), circa

5 km south of Maprik, 700 feet (= 213 m),East Sepik Province, Papua New Guinea.”

Holotype of H. ziegleri was initially referred to H. hussoni . Monotypic.

Distribution. Known only from type locality in foothills of Prince Alexander Range, N New Guinea.

Descriptive notes. Head-body 132 mm, tail 118 mm, ear 13 mm, hindfoot c.27 mm. No specific data are available for body weight. Species of Hydromys are plump, short-limbed, semi-amphibious murines having moderately long and broad hindfeet with partially webbed toes. Ziegler’s Water Ratis the smallest member of genus. Fur on upperparts is short (6-7 mm on anterior part of back) but moderately dense and glossy. Overall fur color is dark brown,with orange-buff tipping to hairs; underparts and insides of limbs gray with ocherous tipping, but chin, throat, and cheeks are adingy white, strongly contrasting with rest of underparts. Fur around vent and base of tail is dark brown. Boundary between flank and belly colorations is abrupt. Head is broad and somewhat flattened, with no obvious neck. Vibrissal pads dark; vibrissae numerous but fine, reaching to ear. Eyes are moderately reduced; ears moderate-sized, dark and thinly furred. Front feet with nail on first digit, and unpigmented claws, all strongly curved and sharp, on other digits; hindfeet are elongate and broad, upper surface with dark pigment and pale fine hairs, all digits bearing unpigmented claws, strongly curved and sharp, second to fourth digits united by band of conspicuous webbing. Tail is relatively short (89% of head—body length), rounded in cross-section, but not conspicuously thickened, brown above and below, scales flattened and in 13-15 rows per cm at mid-tail; hairs behind scales are short, only c.2-3 scale rows in length, so that tail is much less hairy than that of other Hydromys . Cranium is quite short and stout, with rounded braincase, broad interorbital region, and flattened dorsal profile. Incisors have yellowish-orange enamel, deeper hue in upper than in lower pair; molars reduced to two per quadrat, crowns with “basined” cusp arrangement typical of Hydromys . Mammae two on each side, both inguinal.

Habitat. Type specimen was reported by A. C. Ziegler in 1984 to have been caughtin a garden, with a watercourse in vicinity of the site. Area to immediate S of Maprik in East Sepik Province is a mosaic of subsistence gardens and primary and secondary evergreen tropical lowland rainforest, the original vegetation cover of entire region; landscape is finely dissected, with many small watercourses draining into larger streams that flow S across Middle Sepik Plain to meet the Sepik River, some 50 km distant.

Food and Feeding. No information.

Breeding. No information.

Activity patterns. No information.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Data Deficient on The IUCN Red List. K. M. Helgen in 2005 noted that “type locality lies in the vicinity of the Screw and Amuk Rivers, which drain from the highlands of the Prince Alexander Range and the Torricelli Range, respectively,” and considered it likely that Ziegler’s Water Rat occurs more widely in either or both of these ranges. Although large parts of the Sepik Basin itself are blanketed by “kunai” grassland (dominated by Imperata cylindrica, Ischaemum barbatum, and Themeda traindra [all Poaceae]) of possible anthropogenic origin, the ecologically more productive mosaic habitat type found in vicinity of Maprik is widespread on the Middle Sepik Plain that extends for nearly 300 km along southern flanks of Prince Alexander and Torricelli Ranges. Ziegler’s Water Rat might be sought anywhere in this poorly surveyed area, as well as in rangesto the north.

Bibliography. Gerrie & Kennerley (2016k), Helgen (2005), Ziegler (1984).