211.

Sibuyan Striped Shrew Rat

Chrotomys sibuyanensis

French: Chrotomys de Sibuyan / German: Sibuyan-Streifenratte / Spanish: Rata musarana listada de Sibuyan

Other common names: Sibuyan Striped Chrotomys, Sibuyan Striped Earth-rat

Taxonomy. Chrotomys sibuyanensis Rickart et al., 2005,

“Northwest slope of Mt. Guitinguitin, 6-75 km S, 4-5 km E Magdiwang, Romblon Province, Sibuyan Island, Philippines, 1325 m elevation, 12°26’N, 122°33’E.”

Chrotomys and Rhynchomys of the Philippines were typically allied in the past with the Australo-Papuan water rats ( Hydromys etc.), mainly on account of dental similarities. Their closest phylogenetic affinities, as revealed by molecular studies, are with other, recently discovered Philippine shrew rats and mice of genera Archboldomys and Soricomys, and with the less specialized Philippine murines of genus Apomys . Molecular studies indicate that C. sibuyanensis is not particularly closely related to any other described species within Chrotomys . Monotypic.

Distribution. Sibuyan I, Philippines.

Descriptive notes. Head-body 160 mm,tail 82 mm, ear 19 mm, hindfoot 34 mm; weight 104 g. Known from a single specimen (an adult male). Chrotomoys are stout-bodied, semifossorial murines with short, strong limbs, and thick tail considerably shorter than headbody length; relatively small eyes; ears rounded and relatively short; forefeet proportionally large and with strong digits and heavy, nearly straight claws second to fourth digits; hindfeet long and narrow with small plantar pads and claws on all digits; cranium robust, with flask-shaped outline, forward-projecting upper incisors that are probably used for digging, short nasal bones that terminate well behind level of incisors, and molars small, with occlusal pattern consisting of shallow “basins.” The Sibuyan Striped Shrew Rat is a medium-sized member of genus with fur on upperparts dense, soft and relatively short, hair length 13 mm at mid-back; narrow, yellowish-gray stripe along middle of back from between eyes to base oftail (hairs with yellow tipping on blackish-brown bases), a broad blackish-brown lateral zone, and flanks that are lighter grayish brown; underparts are dark yellowish gray withsome patches of lightersilvery gray fur on throat, wrists, chest, and urogenital region, with all hairs gray-based; transition between lateral zone and flank is gradual, but transition to underparts is abrupt; lips with silvery gray to dark gray hairs, cheeks brownish gray; eyelids narrowly edged with black; vibrissae brownish gray, reaching ears; ears blackish gray and sparsely furred with shortsilvery-gray hairs. Feet have upper surfaces unpigmented, bearing fine silvery hairs, digits nearly naked; palmar surface of forefeet unpigmented; hindfeet elongate but shorter relative to body length than those of congeners; plantar surface of hindfeet unpigmented, with six relatively small pads. Tail is very short (51% of head-body length), skin medium brown, slightly paler below and near tip, scales very small, in 22 rows/cm, each scale with three short, brown hairs. Cranium has relatively narrow rostrum and three molars that are proportionally smaller than those of all congeners except Blazed Luzon Striped Shrew Rat ( C. silaceus), the last molar particularly strongly reduced. Females with two pairs of mammae, both inguinal.

Habitat. Evergreen tropical rainforest. According to the species’ describers, the only known specimen was captured on “a steep ridge in a transition zone between montane and mossy forest habitat. Dominant vegetation... included climbing bamboo ( Schizostachyum [ Poaceae]) and a gymnosperm tree ( Podocarpus [ Podocarpaceae])”... and the “understory consisted primarilyof creeping pandan ( Freycinetia [Pandanaceael]).” Sibuyan has an area of 445 km” and two peaks: Mount Guiting-Guiting, with height of 2058 m, and Mount Nailog, with height of¢.790 m.

Food and Feeding. No information.

Breeding. The adult male specimenhad enlarged testes measuring 20 mm x 12 mm when captured on 8 March 1992.

Activity patterns. The only known specimen was fresh when found in a snap-trap at 16:00 h, and was very likely active during day.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Data Deficient on The IUCN Red List. Natural habitats on Sibuyan have been modified by forestry and agricultural practices. Primary forests currently cover ¢.33% of the land area of the island, and much of the surviving forest is enclosed within Mount Guiting-Guiting Natural Park. Montane forest begins at ¢.700 m elevation, grading upward into mossy forest, heathland, and montane grassland around peaks.

Bibliography. Goodman & Ingle (1993), Heaney et al. (1998), Kennerley (2016i), Musser & Carleton (2005), Rickart et al. (2005).