182.

Indomalayan Pencil-tailed Tree Mouse

Chiropodomys gliroides

French: Souris-a-pinceau de Malaisie / German: Indomalayische Pinselschwanz-Baummaus / Spanish: Raton arboricola de cola de lapiz de Indomalasia

Other common names: Pencil-tailed Tree Mouse

Taxonomy. Mus gliroides Blyth, 1856,

“Cherra[punji],” E Khasi Hills, Meghalaya State, India.

Chiropodomys gliroides is widespread and geographically variable. Thorough review of morphological variation by G. G. Musser in 1979 suggested primary distinction between populations north and south of Isthmus of Kra, with variation also within each of these geographic areas. Morphological diversity is particularly pronounced among insular Sundaic populations. Chromosomal contrasts reported between populations in Thailand and Malaysia, but taxonomic significance requires further investigation. Genetic analysis of Indochinese populations found deep phylogeographic partitioning of mitochondrial-gene sequence diversity, with maximum divergences of 12% for cytochrome-b gene. Broader geographic and genomic sampling is needed to clarify taxonomic diversity within this complex group. Monotypic.

Distribution. NE India, Myanmar, SW China, Thailand, Laos, Vietnam, NE Cambodia, Peninsular Malaysia, and Indonesia (Pulau Nias, S Sumatra, Kepulauan Tujuh, Kepulauan Natuna, Java, and Bali).

Descriptive notes. Head—body 69-102 mm, tail 94-143 mm, ear 13-19 mm, hindfoot 15-22 mm; weight 15-32 g. A medium-sized species of Chiropodomys, with typical body form for this arboreal genus—short head with large eyes, moderately large ears, and elongate, narrow vibrissae; slender body clothed in short,soft, dense fur with inconspicuous scattered guard hairs; short broad hindfoot with nailed hallux and short, recurved claws on second to fourth digits; elongate, well-furred tail with distinct terminal tuft; and two mammae on each side, both inguinal. All populations of the Indomalayan Pencil-tailed Tree Mouse have brown to reddish-brown fur on upperparts, either white or cream fur on underparts, white to tan foreand hindfeet, and tufted tail that is evenly colored above and below, and lacks any pale tipping. Facial patterning includes buffy fur on cheeks and dark eye-ring. Malay and Sundaic populations are brightly colored, reddish-brown above, pure white below, with intervening ocherousstrip, and tail uniformly brown to dark brown; compared with mainland Asian populations, they are generally smaller but have longer skull with proportionally smaller molar rows and smaller auditory bullae. Populations north of Isthmus of Kra are usually larger-bodied, with longer feet but proportionally shorter tail that is paler brown; upperparts are duller brown to tan, and underparts usually cream rather than white, with no or weakly developed intervening ocherous strip. An individual from Doi Khun Tan in Thailand has prominent black tail brush that terminates in distinct white tip. Juveniles have shorter and finer pelage, dorsum grayish brown andventer white or cream. Karyotypes of individuals from Peninsular Malaysia with 2n = 42, with 18acrocentric pairs, one metacentric pair, and one submetacentric pair; and metacentric X and submetacentric Y chromosomes that are both unusually large; FN = 48; nucleolar organizer regions occur on one acrocentric pair and one metacentric pair. Specimens from Thailand with 42 telocentric chromosomes; FN = 42; Y chromosome entirely heterochromatic. In both chromosomaltypes, pericentromeric regions of most autosomes with C-banding heterochromatin. Spermatozoa measure 102 pm in total length, head short with 5 pm hook, midpiece relatively short (22 pm); overall, resemble spermatozoa of Mus species.

Habitat. Indomalayan Pencil-tailed Tree Mice are found in numerous habitat types, including lowland evergreen, semi-evergreen and deciduous tropical forests, and hill to lower montane tropical forests. They occur in both primary and secondary forests and plantations, and are sometimes captured in close proximity to human habitations, sometimes inside dwellings. Many captures have been made in areas of secondary forest with bamboo understory. Occurs at elevations from sea level to more than 1615 m.

Food and Feeding. Stomach of one individual contained “nutty material,” and a primary reliance on high-protein seedsis further indicated by combination ofrelatively strong incisors and small molars with complex occlusal pattern. Individuals have been maintained for long periods in captivity on mixed diet of roots, sweet potato, grain, unhusked rice, green vegetables, and soft fruits (including banana, papaya, pineapple); fresh bones, raw meat and meal worms were also consumed. On such a diet, drinking water was not required.

Breeding. Information collected during 1948-1952 in Selangor State, Peninsular Malayasia, showslittersizes of 1-3 (modally 2), and concentration of breeding activity within first quarter ofyear. Subsequent analysis of a larger dataset ofwild-caught individuals suggested fluctuations in breeding intensity but “no annually recurrent period during which pregnancies never occur.” Laboratory studies also demonstrated polyestry (with estrous cycle of about one day) and short gestation period of ¢.19-21 days. A neonate weighed 2-8 g and fur was present byfifth day; weaning commenced at c.17 days and at body weights of9-11 g; sexually mature size was attained at ¢.100 days. Mean lifespan in the wild estimated to be 23-8 months. Captive individuals bred in London Zoo lived a maximum of 43 months. In various localities acrossits range, this species has been reported to construct and occupy leaf-filled nests within internodes of standing bamboo culms,either fresh or dry, and with diameters down to 6-5 cm. These spaces are accessed by a gnawed,circular hole with diameter ¢.2-5 cm; additional gnawed holes sometimes connect several internodal spaces, occasionally leading to secondary entrances; area around access holesis otherwise unmodified. Two or more nests of increasing age have been observed within a single culm, but it is not known whether or not these were occupied by same or different individuals. Although distinctive, this behavioris not obligatory, as there are reports of Indomalayan Pencil-tailed Tree Mice building leaf nests in tree hollows and in crowns of palms.

Activity patterns. Indomalayan Pencil-tailed Tree Mice are nocturnal and primarily arboreal but are sometimes trapped on forest floor. There are records from upland rice fields, presumably of individuals foraging from nests situated in adjoining forests.

Movements, Home range and Social organization. Movements of Indomalayan Penciltailed Tree Mice were studied in Selangor, Malaysia, by means of mark-recapture trapping methods. Most captures were associated with bamboo clumps, and mean distance traveled for all individuals captured twice or more was 12-1 m (range 3-28 m). It was concluded thatthis speciesis “behaviorally confined to a spatial area not exceeding twice its specialized niche requirements” (i.e. the bamboo clumps), but dispersal capacity of a species that relies on such a narrow and ephemeral microhabitat was questioned. Although this observation remains valid locally, the wider records for the Indomalayan Pencil-tailed Tree Mouse clearly demonstrate its capacity to exist within and disperse across a much wider range of habitats. Solitary lifestyle inferred from capture records in nests of single adults or females with dependent young. Violent behavior when “unfriendly” individuals were housed together, often resulting in deaths, was also reported.

Status and Conservation. Classified as Least Concern on The IUCN Red Lust.

Bibliography. Agrawal (2000), Badenhorst et al. (2009), Blyth (1856, 1859), Corbet & Hill (1992), Dang Huy Huynh et al. (1994), Ellerman (1941, 1961), Harrison (1955, 1969), Jarvis & Morris (1961), Lunde & Nguyen Truong Son (2001), Lunde et al. (2003), Marshall (1977b), Medway (1964a, 1969), Meschersky et al. (2016), Miller (1903b), Musser (1979), Osgood (1932), Peters (1869), Robinson et al. (1995), Rudd (1965, 1966a, 1966b, 1979), Smith et al. (2004), Thomas & Wroughton (1909), Tsuchiya et al. (1979), Wang Yingxiang (2003), Yong (1973, 1983), Yong et al. (2012), Van Peenen et al. (1969), Wroughton (1915), Wu Deling & Deng Xiangfu (1984), Zhang Yongzu et al. (1997).