Rattus tanezumi (Temminck, 1845)

Don E. Wilson, Russell A. Mittermeier & Thomas E. Lacher, Jr, 2017, Muridae, Handbook of the Mammals of the World – Volume 7 Rodents II, Barcelona: Lynx Edicions, pp. 536-884 : 831

661.

Oriental House Rat

Rattus tanezumi

French: Rat tanezumi / German: Asiatische Hausratte / Spanish: Rata caseraoriental

Other common names: Oriental Rat, Oriental Roof Rat, Tanizumi Rat

Taxonomy. Mus tanezumi Temminck, 1844 ,

“japonais est Ta-nezumi.” Interpret- ed by J. K. Jones, Jr. and D. H. Johnson in 1965 as “Japan ... vicinity of Nagasaki on the southern island of Kyushu.”

Taxonomy of R. tanezum: and the entire R. rattus species complex ( R. rattus and its relatives) is in flux, with possibly 4-6 distinct species in the R. rattus complex. As outlined under R. rattus , there are six main lineages within the R. rattus clade and four distinct species: R. rattus (Lineage I, 2n = 38), R. tanezumi (Lineage II, III and IV, 2n = 42 and 2n = 40 in Sri Lankan Lineage IV), R.sakeratensis (Lineage V) , and R. tiomanicus (Lineage VI) . Lineage II is the most widespread, probably originating in northern and western South-east Asia and southern China, Hainan, and Taiwan, spreading throughout China, Japan (including Ryukyu Islands), and various parts of Indonesia, Philippines, and Melanesia. Lineage III probably originated in northern parts of the Indian Subcontinent, being found in modern times only surrounding Himalayan region, including north-eastern Afghanistan, northern Pakistan, northern India, south-western China, Nepal, and Bhutan. Lineage IV, which is the most geographically complex lineage, probably originated in southern South-east Asia, spreading currently throughout Indonesia and Philippines, although its present in Sumatra, Borneo, and many small islands is uncertain. Lineage IV is also found in Sri Lanka, probably coming from Java or mainland south-eastern Asia. As currently understood genetically, Lineage 1 is sister to Lineage II, both of which are sister to Lineage III. The clade containing Lineages I-III are sister to a clade including Lineage IV-VI, and Lineage IV and V are sister to one another, with Lineage VI assister to them both. This phylogeny leaves R. tanezumi paraphyletic. It probably will be split into three distinct species, or lumped into R. rattus with about four subspecies. Taxonomy requires further investigation.

Distribution. Native distribution ranged from E Afghanistan through N &NE India, Nepal, Bhutan, and N Bangladesh into C & China (including Hainan I), Korean Peninsula, and mainland SE Asia including many offshore Is S to the Isthmus of Kra; presently unclear whether the species is native or introduced to Taiwan and Japan. Native and introduced distributions are currently unresolved, especially because there are probably three distinct species, currently recognized as lineages. Introduced into in the Andaman and Nicobar Is, Peninsular Malaysia and Sunda Shelf Is, Philippines, W New Guinea, Eniwetok and Fiji within Micronesia and Palau, although these seem to be more recent than other introductions. Specimens from South America and S California , USA, have been genetically identified as this species, probably originating from individuals transported there by boats in recent times. Because of ambiguity between when species were introduced and confusion as to what populations are native or not, the more ancient introduced distribution of the speciesis included in the distribution map throughout Indonesia and Melanesia, but not in other regions where the species has been introduced more recently (North America, South Africa, and Micronesia).

Descriptive notes. Head—body 105-215 mm, tail 120-230 mm, ear 17-23 mm, hindfoot 17-23 mm; weight 100-200 g. The Oriental House Rat is a typical medium-sized species of Rattus , very similar to the Roof Rat ( R. rattus ). Pelage is short, sleek, and coarse, with mixed pale brown and black-tipped hairs throughout. Dorsum is usually various shades of brown and black, being less variable than is typical on Roof Rats. Venter is usually grayer white (but always white), with individual hairs having gray bases and buffy white tips. Ventral pelage is not sharply demarcated from dorsal pelage. Feet have darkgrayish brown stripe dorsally, being white on sides and fingers. Ears are dark and mostly hairless; vibrissae are long and stiff. Tail is ¢.109% of head-body length, scaly, and naked, being mostly unicolored brown, but ventral part of base can be slightly paler. Skull is similar to that of the Roof Rat. Various mites (including more than 50 species of gamasid mites), lice (Polyplax and Hoplopleura are common), fleas, and ticks have been recorded from the Oriental House Rat, as well as many endoparasites, including Taenia taeniaeformis (liver cestode), Rodentolepis (tapeworm in the duodenum), Raillietina garrison: (tapeworm in the small intestines), Angiostrongylus cantonensis (rat lungworm/nematode in lungs and pulmonary arteries), Nippostrongylus muris (intestinal nematode), Euparyphium (trematode in the small intestine), among others. There are five pairs of mammae: one pectoral, one post-axillary, one abdominal, and two inguinal. Chromosomal complement is 2n = 42, FN = 60 (most populations) or 2n = 40 (Sri Lankan population, with FN data not available).

Habitat. Human settlements and primary and secondary habitats in more tropical parts of its distribution and generally restricted to human settlements, agricultural areas, and cities in colder regions, from sea level to elevations of ¢.2000 m.

Food and Feeding. Oriental House Rats are highly adaptive and omnivorous, with similar food habits as the Roof Rat. They eatjust about anything, although they prefer more plant foods than animal foods and readily eat human trash.

Breeding. Reproduction of the Oriental House Rat occurs year-round. Gestation is ¢.weeks, and litters usually have 3-7 young. Eyes open at c.15 days old. Young can eat solid food at ¢.3 weeks old, are weaned at c.1 month, and reach sexual maturity as early as three months. Females reach maturity at weights of 80-100 g, although a minimum weight of 50 g has been reported.

Activity patterns. The Oriental House Ratis primarily nocturnal, but in areas with high densities (cities in particular), it can be seen during the day. Most activity occurs early at night, usually before midnight. It is mostly arboreal and scansorial, generally making nests aboveground in walls, roofs, trees, bushes, and other dark and secluded areas.

Movements, Home range and Social organization. Nests usually contain many individuals, with dominant individuals having better access to food and mates. The Oriental House Rat is probably ecologically similar to the Roof Rat; most ecological studies within the R. rattus species complex have been done on Roof Rats in Europe.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Oriental House Rat is a vector for many disease and highly invasive, being a risk to native species and an agricultural and urban pest. Throughout its native and introduced distribution, it is vigorously trapped and poisoned to attempt to control populations, which are increasing across its distribution.

Bibliography. Andru et al. (2013), Antolin et al. (2009), Aplin, Brown et al. (2003), Aplin, Suzuki et al. (2011), Balakirev & Rozhnov (2012), Bastos et al. (2011), Flannery (1995a, 1995b), Heaney & Molur (2016), Heaney et al. (1998), Huang Ligin et al. (2013) , Jones & Johnson (1965), Musser & Califia (1982), Musser & Carleton (2005), Musser & Newcomb (1983), Pages et al. (2013), Robins, Hingston et al. (2007), Robins McLenachan et al. (2008), Sinniah (1979), Smith & Yan Xie (2008), Stuart et al. (2012), Yong (1969).

Figures

Distribution. Native distribution ranged from E Afghanistan through N &NE India, Nepal, Bhutan, and N Bangladesh into C & China (including Hainan I), Korean Peninsula, and mainland SE Asia including many offshore Is S to the Isthmus of Kra; presently unclear whether the species is native or introduced to Taiwan and Japan. Native and introduced distributions are currently unresolved, especially because there are probably three distinct species, currently recognized as lineages. Introduced into in the Andaman and Nicobar Is, Peninsular Malaysia and Sunda Shelf Is, Philippines, W New Guinea, Eniwetok and Fiji within Micronesia and Palau, although these seem to be more recent than other introductions. Specimens from South America and S California , USA, have been genetically identified as this species, probably originating from individuals transported there by boats in recent times. Because of ambiguity between when species were introduced and confusion as to what populations are native or not, the more ancient introduced distribution of the speciesis included in the distribution map throughout Indonesia and Melanesia, but not in other regions where the species has been introduced more recently (North America, South Africa, and Micronesia).