188.

Luzon Cordillera Forest Mouse

Apomys abrae

French: Apomys d’Abra / German: Cordillera-Philippinenwaldmaus / Spanish: Raton de bosque de Luzon

Other common names: Cordillera Pine Forest Mouse, Luzon Cordillera Apomys

Taxonomy. Rattus (Apomys) abrae Sanborn, 1952,

“Massisiat, altitude 3500 feet [= 1067 m |], Abra Province, Luzon Island, Philippine Islands.”

Apomys abrae is a member of subgenus Megapomys, erected by L. R. Heaney and cow-orkers in 2011. Originally described as a species of subgenus Apomys within Rattus, reflecting J. R. Ellerman’s mistaken view that many Murinae of generalized body form and cranio-dental morphology were closely related to core species of genus Rattus . The combination Apomys abrae was first used by D. H. Johnson in 1962. A. abrae is not fully differentiated from A. datae in published mitochondrial sequences, but this is interpreted as evidence of introgression following occasional hybridization on Mount Data. Genetic and morphometric analyses failed to identify any strong phylogeographic structure within the range of A. abrae . Currently regarded as monotypic but in need of further assessment.

Distribution. Cordillera Central of N Luzon I, N Philippines.

Descriptive notes. Head-body 121-141 mm, tail 120-144 mm,ear 21-24 mm, hindfoot 33-39 mm; weight 50-79 g. Published mensural data demonstrate weak male-biased sexual dimorphism in external and cranio-dental measures for this species.

Apomys species are soft-furred, small to medium-sized murines with relatively unspecialized body form; they are distinguished from other Philippine murines by a distinctive suite offeatures, 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 1nguinal, and a simplified molar pattern with cusps united into transverse laminae. Members of subgenus Megapomys are larger, shorter-tailed species that are active primarily on ground; in most forest habitats across Luzon, they are the most abundantterrestrial mammalin any local community. The Luzon Cordillera Forest Mouse is a medium-sized Megapomys. Fur on upperparts, flanks, and outer surfaces of foreand hindlimbsis rich dark brown with slight rusty tint and black flecking, body hairs dark gray basally, guard hairs black and narrowly projecting through fur; fur on underparts and inside of foreand hindlimbs dark gray at bases, with white tips; upperside and lower parts with sharply defined boundary. Dark fur of limbs does not extend onto upper surfaces of foreand hindfeet, which are unpigmented and covered with short white hairs, sometimes lightly peppered with black; hindfeet relatively elongate and narrow, undersurface with pale gray pigment for proximal half, plantar pads small and well separated, digits relatively long. Tail is relatively long (averaging 97-101% of head-body length), dark above and white below for entire length,tail hairs dark on upper surface but all white on underside. Cranium is smaller than that of most Megapomys, with moderately short and slender rostrum and relatively large molars. Chromosomal complement has 2n = 44 and FN = 54, autosomes including two pairs large submetacentric, two pairs small subtelocentric, one pair very small metacentric, remainder telocentric; X and Y chromosomes both telocentric, X large, Y very small. This karyotype originally reported by E. A. Rickart and Heaney in 2002 as belonging to the Northern Luzon Forest Mouse ( A. datae).

Habitat. [Luzon Cordillera Forest Mice have been recorded in dense evergreen montane rainforest, mixed grass and shrubs beneath pines, and in pine forest with broadleaf understory, at elevations of 925-2200 m. In southern part of Central Cordillera, where it co-occurs with the Northern Luzon Forest Mouse between 900 m and 1650 m, the Luzon Cordillera Forest Mouse is generally found at lower elevations and in relatively drier and more open habitats.

Food and Feeding. According to Heaney and coworkers in 2016, Luzon Cordillera Forest Mice are “omnivorous, consuming seeds, insects, and earthworms.” Breeding. Heaney and coworkers reported in 2016 that “four pregnant females had an average oftwo embryos (range = 1-3).” Activity patterns. Luzon Cordillera Forest Mice are nocturnal and have been reported as foraging on surface of ground.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Locally abundant in both primary and disturbed habitats.

Bibliography. Heaney, Balete, Dolar et al. (1998), Heaney, Balete & Rickart (2016), Heaney, Balete, Rickart, Alviola et al. (2011), Johnson (1962), Justiniano et al. (2015), Kennerley (2016e), Rabor (1955), Rickart & Heaney (2002), Rickart, Balete & Heaney (2007), Rickart, Balete, Rowe & Heaney (2011), Rickart, Heaney et al. (2011), Sanborn (1952a).