201.

Small Luzon Forest Mouse

Apomys microdon

French: Apomys de Catanduanes / German: Kleinzahn-Philippinenwaldmaus / Spanish: Raton de bosque pequefo de Luzon

Other common names: Small Luzon Apomys

Taxonomy. Apomys microdon Hollister, 1913,

“Biga [= Viga], CatanduanesIsland,” Catanduanes Province, Bicol Region, Philippines.

Apomys microdon, a member of subgenus Apomys, 1s most closely related to A. musculus . G. B. Corbet and |]. E. Hilllisted this species in 1992 as Apomys hollisteri, a name proposed by J. R. Ellerman within Rattus as a replacement for microdon on grounds that latter name was preoccupied by Mus microdon (a member of African genus Mastomys that Ellerman also placed within Rattus). As correctly assessed by G. G. Musser in 1982, removal of both of these names from Rattus dissociates them from each other and thus allows use of the combination Apomys microdon, with: Rattus (Apomys) hollisteri as a junior synonym. A. microdon is very likely a species complex,as yet incompletely sampled or understood across its geographic range. Musser in 1982 associated samples from Dinagat and Leyte with A. microdon, whereas E. A. Rickart and others referred samples from Biliran, Bohol, and Leyte to A. lttoralis, these populations probably represent one or more undescribed species, related to A. microdon . On Luzon, A. microdon is sympatric with various members of subgenus Megapomys which are more strictly terrestrial, contrasting with the scansorial to arboreal members of subgenus Apomys . Currently regarded as monotypic but in need offurther assessment.

Distribution. Luzon and Catanduanes Is, Philippines.

Descriptive notes. Head-body 90-107 mm, tail 124-149 mm, ear 15-19 mm, hindfoot 26-31 mm; weight 28-42 g. Apomys species are soft-furred, small to medium-sized murines with relatively unspecialized body form; distinguished from other Philippine murines by a distinctive suite of features, including long, narrow hindfeet with sharp, recurved claws on all digits, thinly furred tail with weakly overlapping scales and three hairs per tail scale, unreduced eyes, relatively large and thinly furred ears, vibrissae on snout very elongate and, folded back, reach to shoulder or beyond, reduction to two mammae on each side, both inguinal, and a simplified molar pattern with cusps united into transverse laminae. Members of subgenus Apomys are small, long-tailed, and active primarily in canopy. The Small Luzon Forest Mouse, one of smallest and more brightly colored members of subgenus, has fur on upperparts, flanks, and outer surfaces of limbs overall tawny brown and lightly flecked with black, guard hairs black and narrowly projecting through fur; fur on underparts and inside of limbs of variable coloration, some bright orange brown to bases, others buff but with pale to dark gray bases to hairs, occasional individuals have white patches on chest and midline of abdomen; upperside and underside with sharply defined boundary. Tail is considerably longer than head-body length, brown above to tip but variably brown, mottled, or pale brown to white below; scales small; upper surfaces of foreand hindfeet pale brown, sparsely haired.

Habitat. Recorded fromprimary evergreen tropical rainforest, ranging from lowland rainforest and hill forest to montane forest; extends into mossy forest only when other species of subgenus Apomys are absent. Occurs also in patches of secondary forest, regenerating after natural or anthropogenic disturbance, but not outside forest cover. On Luzon, Small Luzon Forest Mice are found from sea level to 2025 m, but with lower elevational cut-off where A. musculus (also a member of subgenus Apomys) is present in the montane forests.

Food and Feeding. Dietary focus of the Small Luzon Forest Mouseis said to be seeds, with occasional consumption of insects and earthworms.

Breeding. Pregnant females are reported with 1-3 embryos (modally 2). Adult males reportedly have small testes, measuring 4 mm x 8 mm. Reports of nests constructed from “dry bamboo leaves, with a few leaves from broad-leafed trees,” and located in axils of Pandanus palms and in clumps of climbing bamboos.

Activity patterns. The Small Luzon Forest Mouse is said to be active at night, most often in trees but sometimes on ground.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Small Luzon Forest Mice are recorded from numerous localities on Luzon and can be moderately common in suitable habitat. Lowland parts of this species’ range have suffered severe deforestation, but remaining habitats at higher elevations are not under any immediate threat.

Bibliography. Corbet & Hill (1992), Danielsen et al. (1994), Ellerman (1941), Heaney (2016¢), Heaney, Balete, Dolar et al. (1998), Heaney Balete, Gee et al. (2005), Heaney, Balete & Rickart (2016), Hollister (1913), Justiniano etal. (2015), Musser (1982a), Musser & Carleton (1993, 2005), Rickart et al. (1991).