685.

Malaysian Field Rat

Rattus tiomanicus

French: Rat de Tioman / German: Malaiische Feldratte / Spanish: Rata de campo de Malasia

Other common names: Malayan Field Rat, Tioman Rat

Taxonomy. Mus tiomanicus G. S. Miller, 1900,

“Tioman Island [Pahang, Malaysia].”

Rattus tiomanicus 1s sister to R.sakeratensis

and Lineage IV of R. tanezumi within the

rattus clade in the R. rattus species group

(representing Lineage VI, see R. rattus and R. tanezumi). A specimen of R. baluensis included in a recent genetic study clustered in R. tiomanicus, which could indicate that R. baluensis is better included in R.tiomanicus . R. simalurensis might also be included in R.tiomanicus as an island variant, although further revision is needed. Rattus tiomanicus has substantial geographical variation, and it might represent multiple species or at least subspecies. Subspecific taxonomy requires further investigation.

Distribution. Malay Peninsula, Sumatra, Palawan (and adjacent Bancalan, Arena, Busuanga, and Calauit Is), Borneo, Java, Bali, many smaller offshore Is (Tioman, Enggano, Maratua Archipelago, Panjang, Rabu Rabu, Sangka Laki, Bilang Bilangan, Eraban, and Miang Besar), and perhaps Busuanga I.

Descriptive notes. Head-body 140-190 mm, tail 150-200 mm, ear 20-4 mm, hindfoot 28-35 mm; weight 55-150 g. The Malaysian Field Rat is medium-sized, with sleek and smooth pelage and short stiff spines and shortish black guard hairs throughout, but shorter than those of the Roof Rat ( R. rattus). Dorsum is grizzled olive-brown to reddish brown, being variable between populations and becoming lighter on sides. Venter is white with buffy white hair tips or grayish white with gray-tipped hairs; venteris demarcated from dorsum but notsharply. Feet are broad and completely white. Ears are long and lighter than dorsum, being lightly furred; vibrissae are long. Tail is 95-120% of head-body length and unicolored dark brownish black. Skull is long, with relatively thin rostrum. The pinworm Syphacia muris has been recorded from the Malaysian Field Rat. There are five pairs of mammae: one pectoral, one post-axillary, one abdominal, and two inguinal. Chromosomal complement is 2n = 42, FN = 62 or 64.

Habitat. Secondary and coastal forests, plantations, gardens, scrubland, grassland, grassland-forest mosaic, selectively logged forest, rice fields, mossy forest, and transition zone between mossy and montane forest. The Malaysian Field Rat is mostly found in lowland habitats and rarely houses.

Food and Feeding. The Malaysian Field Rat eats various plants and animals. A recent study in palm oil plantations found that it eat the palm fruit, making it an agricultural pest.

Breeding. Malaysian Field Rats apparently reproduce year-round, with a peak in December—January. Females become sexually active at weights of 30-50 g; males become sexually active at ¢.60 g. Average number of embryos in a population in a palm oil plantation was 4-4;litters had 2-7 young.

Activity patterns. The Malaysian Field Rat is nocturnal and feeds at night. It is mainly arboreal, although it also spends a lot of time on the ground. A study of a population in a palm oil plantation found nests in palm oil fronds.

Movements, Home range and Social organization. Malaysian Field Rats lived at high densities within a palm plantation, with 183-539 ind/ha (average 305 ind/ha).

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Malaysian Field Rat has a large distribution,is very common,is found in many protected areas, and is considered an agricultural pest in many regions, especially to stored grain and in palm oil plantations.

Bibliography. Aplin (2016m), Aplin, Brown et al. (2003), Aplin, Chesser & ten Have (2003), Aplin, Suzuki et al. (2011), Balakirev & Rozhnov (2012), Esselstyn et al. (2004), Francis (2008), Krishnasamy et al. (1980), Musser & Carleton (2005), Pages et al. (2013), Phillipps & Phillipps (2016), Sinniah (1979), Wood (1984), Wood & Liau (1984), Yong (1969), Yong et al. (1972).