193.

Northern Luzon Forest Mouse

Apomys datae

French: Apomys du Data / German: Mount-Data-Philippinenwaldmaus / Spanish: Ratén de bosque de Luzon septentrional

Other common names: Cordillera Forest Mouse, Luzon Montane Forest Mouse, Northern Luzon Apomys

Taxonomy. Mus datae A. B. Meyer, 1899,

“Berge Data, Lepanto, Nord Luzon [Island], von 8000 Fuss [= Mount Data, Mountain Province, Luzon Island, Philippines, 2438 m].”

Apomys datae was included variously in Mus, Epimys, and Rattus before J. R. Ellerman correctly affiliated datae with hylocoetes, placing them in subgenus Apomys of Rattus . D. H. Johnson in 1962 was the first to use the combination Apomys datae . G. S. Miller described Apomys majorin 1910 from a single specimen and without comparing it with Meyer's taxon; its similarity to A. dataewas noted by G. G. Musser in 1982, a conclusion upheld by all subsequent analyses. A. dataeis not fully differentiated from A. abrae on published mitochondrial sequences, but this is interpreted as evidence of introgression following occasional hybridization on Mount Data. Genetic and morphometric analyses demonstrate phylogeographic structure among the various isolated populations of A. datae . This speciesis sympatric with A. abrae over a relatively narrow elevational band between 1500 m and 1650 m, but the two species are generally segregated locally by habitat, A. datae favoring wetter, more closed situations. Currently regarded as monotypic but in need of further assessment.

Distribution. Recorded from high elevations in the S two-thirds of the Cordillera Central, NW Luzon I, Philippines. Previous accounts of A. datae in the Sierra Madre and in the lowlands of Luzon refer to other species of Apomys that remained unrecognized until 2011.

Descriptive notes. Head—body 125-155 mm, tail 121-139 mm, ear 18-23 mm, hindfoot 33-39 mm; weight 63-105 g. Males average slightly more than females for all measurements, including weight (87-8 g vs. 77-2 g). Species of Apomys 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, thinly furred tail, 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 Megapomys are larger, shorter-tailed species that are active primarily on ground; in most forest habitats across Luzon, they are the most abundant terrestrial mammal in any local community. The Northern Luzon Forest Mouse is a medium-sized Megapomys. Fur on upperparts is dark brown with slight rustyorange tint and fine black flecking, the latter produced by short black guard hairs, body hairs with dark gray bases; fur on underparts and on inside of limbs is dark gray at base with white or buff tipping; upperside and venter colors with sharply defined boundary; skin oflips, lower snout, and base of ears darkly pigmented; dark fur of limbs extends part way onto upper surfaces of foreand hindfeet, but digits unpigmented and with short white hairs, sometimeslightly peppered with black; hindfeet are relatively elongate and narrow, undersurface with dark gray pigment for proximal half, digits relatively short and stocky, plantar pads moderately large but well separated. Tail is relatively short (on average 89-95% of head-body length in various populations), dark above and white below for entire length, with dark tail hairs on undersurface. Cranium is larger and more robust than that of most Megapomys, with long, stout rostrum but relatively small molars. Chromosomal complement has 2n = 44 and FN 2 54, detail not well documented but probably most similar to arrangement in A. abrae . A karyotype originally reported by E. A. Rickart and L.. R. Heaney in 2002 as an exemplar of A. dataeis now attributed to A. abrae .

Habitat. Abundant in evergreen tropical montane forests, including both montane and “mossy” types distinguished in Philippine ecological literature. It occurs also in related secondary forest communities, as well as in shrubby habitats adjacent to agricultural fields, but is generally absent from the agricultural landscape and from pine forest (except when broadleaf forest is regenerating below pine canopy). Elevational limits are 1500-2800 m.

Food and Feeding. Diet reported consists of earthworms,insects, and seeds.

Breeding. Heaney and coworkers reported in 2016 that “twenty-one pregnant females had an average of 1:66 embryos (range =1-3).” The type specimen contained “two small foetuses.” Activity patterns. The Northern Luzon Forest Mouse is reported as being nocturnal and foraging on ground.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List. This species is locally abundant in both primary and disturbed habitats, and is recorded from various protected areas, including Mount Pulag National Park.

Bibliography. Danielsen et al. (1994), Ellerman (1941), Heaney (2016a), Heaney, Balete, Dolar et al. (1998), Heaney, Balete, Gee et al. (2005), Heaney, Balete & Rickart (2016), Heaney, Balete, Rickart, Alviola et al. (2011), Heaney, Balete, Rickart, Veluz & Sarmiento (2004), Heaney, Balete, Rosell-Ambal et al. (2013), Johnson (1962), Justiniano et al. (2015), Mallari & Jensen (1993), Miller (1910), Musser (1982a), Musser & Carleton (1993, 2005), Rabor (1955), Rickart & Heaney (2002), Rickart, Balete, Rowe & Heaney (2011), Rickart, Balete & Heaney (2007), Rickart, Heaney et al. (2011), Sanborn (1952a), Stuart et al. (2007).