213.

Montane Striped Shrew Rat

Chrotomys whiteheadi

French: Chrotomys de Whitehead / German: Luzon-Bergstreifenratte / Spanish: Rata musarana listada de montana

Other common names: Cordillera Chrotomys, Cordillera Striped Rat, Luzon Montane Striped Shrew Rat, Luzon Striped Rat, Montane Chrotomys

Taxonomy. Chrotomys whiteheadi Thomas, 1895,

“highlands ofNorthern Luzon.” Restricted by O.Thomas in 1898 to “Monte Data, Lepanto, [N. Luzon Island], 8000 feet [= 2438 m],” Philippines .

Chrotomys whiteheadis the type species of the genus. In the past, Chrotomys and Rhynchomys of the Philippines were typically allied with the Australo-Papuan water rats ( Hydromys etc.), mainly on account of dental similarities. Their closest phylogenetic

affinities, as revealed by molecular studies, are with other, recently discovered Philippine shrew rats and mice of genera Archboldomys and Soricomys, and with the less specialized Philippine murines of genus Apomys . Monotypic.

Distribution. Cordillera Central, Mt Palali in Caraballo Mts, and Mt Anacuao in S Sierra Madre, N Luzon I, Philippines.

Descriptive notes. Head-body 144-177 mm, tail 95-133 mm, ear 23-27 mm, hindfoot 35-42 mm; weight 73-160 g. Chrotomys are stout-bodied, semi-fossorial murines with short, strong limbs and a thick tail considerably shorter than head-body length; relatively small eyes; rounded and relatively short ears; forefeet proportionally large and with strong digits and heavy, nearly straight claws on second to fourth digits; hindfeet long and narrow, with small plantar pads and claws on all digits; cranium robust, with flask-shaped outline, forward-projecting upper incisors that are probably used for digging, short nasal bones terminating well behind level of incisors, and small molars with occlusal pattern consisting of shallow “basins.” The Montane Striped Shrew Rat, one of the larger members of genus, has fur on upperparts dense, soft, and fluffy, 16-18 mm in length at mid-back, and with broad ocherous-brown medial stripe that runs from between eyes to base oftail, strongly defined blackish-brown or deep brown lateral stripes, and deep ocherous brown on flanks and sides of head; underparts silvery dark gray overlaid with deep bufty wash or grayish dark brown, transition from flanks to underparts gradational; no eye-ring; vibrissae reach just past ears; ears brown and sparsely furred. Feet have upper surfaces with dark brown and silvery-gray hairs; plantar surface with six wellformed pads. Tail is relatively short (58-79% of head-body length), skin brown or blackish brown above and uniformly paler or mottled below, scales small, in 16-18 rows per cm, each scale with three short,silvery hairs. Cranium has relatively broad rostrum; three molars in each series, slightly smaller overall than those of the Lowland Striped Shrew Rat ( C. mindorensis), and the third very strongly reduced. Females have two pairs of mammae, both inguinal. Chromosomal complement has 2n = 38 and FN = 52, and includes two pairs of small metacentric, four pairs of medium-sized to large submetacentric, one pair of large subacrocentric, and twelve pairs of acrocentric chromosomes, the last graded from large to small. The X and Y chromosomes cannot be distinguished from the autosomes and must be among the acrocentric series.

Habitat. Evergreen tropical rainforests, including primary and secondary montane and mossy forest types distinguished in the Philippine ecological literature. According to L.. R. Heaney and coworkers, writing in 2016, Montane Striped Shrew Rats “are highly tolerant of habitat disturbance, often occurring in shrubby second growth and agricultural areas.” Elevational range 900-2700 m.

Food and Feeding. Reported to feed on “earthworms, snails, and other invertebrates, including golden apple snail (Pomacea canaliculata).” R. Joshi and coworkers reported consumption in captivity of golden apple snails and suggested that the Montane Striped Shrew Rat (mistakenly reported as Lowland Striped Shrew Rat) “almost certainly has a beneficial impact on the agricultural system by helping to control invertebrate pests.” Breeding. Heaney and coworkers reported in 2016 that four pregnant females had one (n= 1) or two (n= 3) embryos, and that males have testes that are, compared with other groups of Philippine native murids, large in relation to their body size. They reported also that individual Montane Striped Shrew Rats sometimes plug a burrow entrance by piling up dirt from inside the burrow.

Activity patterns. Heaney and coworkers reported in 2016 that Montane Striped Shrew Rats are active both by day and by night, “burrowing through humus and soil,” and that their presence is often conspicuous owing to abundance of shallow pits and small piles of dirt where they have dug for food.

Movements, Home range and Social organization. The only specific information available is of an individual that moved more than 100 m in a 24hour period. Roshi and coworkers posited regularforaging movements of this species (reported erroneously as a population of Lowland Striped Shrew Rats) between forest and rice-field habitats in Ifugao Province.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Locally common in both old-growth and heavily disturbed habitats. The type locality on Mount Data Plateau has been heavily modified by agricultural activity, and this species was not detected during a resurvey in 2006. The Montane Striped Shrew Ratis locally sympatric above 1800 m in Central Cordilleran ranges with the Blazed Luzon Striped Shrew Rat ( C. silaceus), but the latter species is usually the more abundant of the two.

Bibliography. Alviola et al. (2011), Heaney (2016f), Heaney, Balete, Alviola et al. (2013), Heaney, Balete, Dolar et al. (1998), Heaney, Balete & Rickart (2016), Heaney, Balete, Rickart, Veluz & Sarmiento (2004), Largen (1985), Musser & Carleton (2005), Musser & Heaney (1992), Musser et al. (1982), Rabor (1955), Reginaldo & de Guia (2014), Rickart & Heaney (1991, 2002), Rickart, Balete et al. (2011), Rickart, Heaney, Balete & Tabaranza (2011), Rickart, Heaney, Goodman & Jansa (2005), Sanborn (1952a), Stuart et al. (2007), femme (1974), Thomas (1898b).