196.

Mindanao Montane Forest Mouse

Apomys insignis

French: Apomys remarquable / German: Mindanao-Philippinenwaldmaus / Spanish: Ratén de bosque de montana de Mindanano

Other common names: Great Apo Mouse, Mindanao Montane Forest Apomys

Taxonomy. Apomys insignis Mearns, 1905,

“Mount Apo at 6,000 feet altitude [= 1829 m], southern Mindanao, Philippine Islands.”

Apomys insignis 1s a member of subgenus Apomys . Form A. bardus, from Mount Bliss in the Grand Malindang Mountains of eastern Mindanao, has usually been treated as a subspecies of insignis, but more recently as a synonym. Mitochondrial sequences do not distinguish A. insignis from sympatric A. hylocoetes from Mount Kitanglad Range, but this may be due to introgression or mitochondrial capture as the two species differ markedly in karyotype; the two are sympatric also at 1829 m on Mount Apo, Mindanao. Currently regarded as monotypic but in need of further assessment.

Distribution. Philippines, where it isrestricted to islands of Mindanao and Dinagat.

Descriptive notes. Head-body 71-123 mm,tail 134-176 mm, ear 18-21 mm, hindfoot 31-35 mm; weight 33-52 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, relative 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 species typically most active in canopy. The Mindanao Montane Forest Mouse has fur on upperparts, flanks and outer surfaces of limbs dense and very soft, without spines or stiff hairs, dark, rich brown with “burnished highlights”; fur on underparts and inside of limbs is variably rich dark buff suffused with dark gray or grayish pale buff, many with pure white patches on midline of chest and abdomen; colors of upperside and underside merge gradually on flanks; ears relatively shorter than in sympatric A. hylocoetes, darkly pigmented, and with short hairs on outer surface; eyes without any conspicuous emargination. Dark fur of limbs extends onto upper surfaces of foreand hindfeet, but digits are unpigmented and covered with shorter white hairs; hindfeet relatively longer and narrower than in other members of subgenus, undersurface lightly pigmented, plantar pads small and well separated, hallucal pad short and positioned farther forward than in A. hylocoetes, digits moderately long and slender, with sharply pointed claws. Tail is relatively long (averaging 130-140% of head-body length), weakly to strongly bicolored to tip or with short white tip, brown above and variably brown, gray or white below, often mottled; tail scales conspicuous, in 13-14 rows per cm neartail base, and usually with three short hairs per scale, hair length increasing toward tail tip but without terminal brush. Cranium is very similar to that of other members of subgenus Apomys, but braincase rounder and more inflated than in sympatric A. insignis . Chromosomal complement has 2n = 36 and FN = 36, and autosomes include five pairs of small to large metacentric, three pairs of submetacentric, and ten pairs of subtelocentric chromosomes graded medium to small. Sex chromosomes not obvious, hence X and Y chromosomes presumably both subtelocentric.

Habitat. Restricted to evergreen tropical forest, including both lowland and montane rainforests, and extending narrowly into mossy forest. The Mindanao Montane Forest Mouse appears to be most common in primary montane forest but occursalso in areas of regeneration after natural and low-intensity anthropogenic disturbance. Its less often encountered in lowland contexts where deforestation has destroyedmuch ofits original habitat. One specimen was captured in a coffee plantation at 899 m on Mount McKinley.

Food and Feeding. No information.

Breeding. No information.

Activity patterns. Many captures of Mindanao Montane Forest Mice have been made on the ground among tree roots, under logs and among boulders. The species’ relatively long tail also points to a significant degree of arboreal activity.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Populations are present in three National Parks (Mount Kitanglad, Mount Apo, and Mount Kalatungan Range). The Mindanao Montane Forest Mouse is widespread on Mindanao, from near sea level to high elevations, but lowland populations are fragmented owing to forest loss. The population on Dinagat remains poorly documented.

Bibliography. Heaney, Balete et al. (1998), Heaney, Tabaranza & Balete (2016), Heaney, Tabaranza, Rickart et al. (2006), Hoogstraal (1951), Justiniano et al. (2015), Mearns (1905), Musser (1982c), Musser & Carleton (2005), Rickart & Heaney (2002), Sanborn (1952a).