763.

Common Hill Rat

Bunomys chrysocomus

French: Bunomys de Hoffmann / German: Gemeine Sulawesi-Bergratte / Spanish: Rata de colina comun

Other common names: Common Bunomys, Yellow-haired Hill Rat

Taxonomy. Mus chrysocomus B. Hoffmann, 1887,

Minahassa, northern Sulawesi, Indonesia.

Bunomys chrysocomus is in the B. chrysocomus group within Bunomys and is sister to B. coelestis . Monotypic.

Distribution. Sulawesi.

Descriptive notes. Head-body 97- 180 mm, tail 90-180 mm, ear 17-28 mm, hindfoot 31-40 mm; weight 55-135 g. The Common Hill Rat is a medium-sized species of compact-bodied, long-headed, and variably colored Bunomys . Pelage is dense, smooth, and soft with relatively short guard hairs. Dorsum is dark brown, with buffy speckling and dark brown and buffy bands on hairs and paler grayish brown sides that fade into ventral pelage; underfur is gray; some individuals are darker brownish black, with slight speckling. Rhinarium and sides of muzzle are brown. Venter is grayish white to gray tinged with pale buff to dark gray washed or saturated with buff or ocherous, usually with gray bases to hairs and unpigmented, pale buff, buffy, or ocherous tip, respectively. Feet are variably colored grayish white, whitish brown, brownish white, or dark brown dorsally; digits are unpigmented, gray based, or rarely white covered in brown hairs. Juveniles have velvety and very dark brownish black dorsal pelage, being dark grayish white ventrally. Ears are rubbery and covered in short hairs and vary from shiny grayto dark gray, dark grayish brown and grayish black to blackish gray. Tail is 85-98% of head-body length and varies in color pattern, being mottled brown dorsally and white for full length ventrally (distinctly bicolored), dark brownish gray dorsally and white ventrally with light speckling (distinctly bicolored), dark grayish brown or dark brown dorsally with white ventrally with moderate or dense grayish brown speckling (distinctly bicolored), densely speckled grayish brown dorsally and slightly less speckled ventrally (appearing grayish brown all over), and dark brown dorsally and slightly paler ventrally (almost completely monocolored). Skull is small and gracile. Sucking lice (Hoplopleura and Polyplax), fleas (Sigmactenus, Stivalius, Gymnomeropsylla, Nestivalius, and Musserella), ticks (Amblyoma, Dermacentor, and Haemaphysalis), chiggers (Walchiella and Leptotrombidium), mites (Histiostoma and Laelaps), pseudoscorpions (Megachernes), trematodes (Schistosoma), and nematodes (Subulura, Heterakis, Syphacia, Gnogylonema, and possibly Protospirurua, Trichurus) have been recorded from Common Hill Rat. There are two pairs of inguinal mammae. Chromosomal complement is 2n = 42, FN = 58.

Habitat. [Lowland and montane evergreen rainforest formations at elevations of 250— 2200 m. Most Common Hill Rats are found in steep and wet hillside forests, on forested terraces bordering streams and rivers, along streams, and sometimes on decaying tree trunks and limbs near streams. They can also be found in drier steep hillside forests and ridgetopsfar from streams, which is rare for Sulawesi murids. A few specimens have been captured in degraded forests.

Food and Feeding. The Common Hill Rat is largely carnivorous, although it also eats some fruits. Earthworms, snails, various arthropods, frogs, lizards, wild bananas, and some other fruits were eaten in captivity, and stomach contents of some individuals included figs, other unidentified seeds and fruits, cockroaches, beetle larvae and adults, geophilomorph centipedes, a macrolepidopteran caterpillar, orthopterans, well-chewed earthworm, some ants, and rhinotermitid termite soldiers. Foraging seemsto be done by digging and rummaging with snout through leaflitter and humus while sticking rostrum into dirt and sniffing. Prey is usually grabbed by incisors and moved to front feet to be immobilized by biting down on head of the organism (frogs, lizards, and insects), then proceeding to eat it. They are rather aggressive with voracious appetites, pouncing on lizards and frogs and grabbing earthworms voraciously with their incisors. The only fruit taken by captive individuals was wild bananas ( Musa sp., Musaceae) and fruit of a canopy tree, Himantandra belgraveana ( Himantandraceae). Various other seeds and fruit pulps were found in the stomachs of individuals, although these were unidentified.

Breeding. Litters have two young that are ¢.30 mm in length when born. In captivity, eyes opened after 17 days, during which young slowly began exploring the cage and became aggressive while the mother remained aggressive, only leaving the nest to quickly grab insects to take back and eat in the nest. Maternal grooming is done by licking fur and biting skin.

Activity patterns. The Common Hill Rat is primarily nocturnal and largely terrestrial. Nests are in underground burrows and made of various plant parts, including dried and fresh leaves and stems.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Although habitat of the Common Hill Rat is threatened by agricultural expansion and logging, it is considered relatively common throughout most of its wide distribution, except for in the north-eastern part. It occurs in Lore Lindu National Park among others.

Bibliography. Cassola (2016af), Dewi & Hasegawa (2010), Fabre et al. (2013), Hasegawa et al. (2014), Musser (1991, 2014), Musser & Carleton (2005).