Rattus tanezumi Temminck 1844

Rattus tanezumi Temminck 1844, in: Siebold, Temminck, and Schlegel, Fauna Japonica, Arnz et Socii, Lugduni Batavorum: 51.

Type Locality: Japan, possibly from near Nagasaki on Kyushu Isl (see Jones and Johnson, 1965).

Vernacular Names: Oriental House Rat.

Synonyms: Rattus alangensis Chasen 1937; Rattus amboinensis Laurie and Hill 1954; Rattus argyraceus Sody 1941; Rattus auroreus Sody 1941; Rattus barussanoides Sody 1941; Rattus benguetensis Hollister 1913; Rattus bhotia Hinton 1918; Rattus brevicaudus Kuroda 1952; Rattus brevicaudus Chakraborty 1975; Rattus brunneus (Hodgson 1845); Rattus brunneusculus (Hodgson 1845); Rattus bullocki Roonwal 1948; Rattus canna (Swinhoe 1871); Rattus coloratus (Hollister 1913); Rattus dammermani Thomas 1921; Rattus dentatus (Miller 1913); Rattus diardii (Jentink 1880); Rattus exsul (Miller 1913); Rattus flavipectus (Milne-Edwards 1872); Rattus fortunatus (Miller 1913); Rattus gangutrianus Hinton 1919; Rattus germaini (Milne-Edwards 1872); Rattus griseiventer (Bonhote 1903); Rattus insulanus (Miller 1913); Rattus kadanus Chasen 1937; Rattus kelleri (Mearns 1905); Rattus khyensis Hinton 1919; Rattus kurokuma Kuroda 1953; Rattus kramensis Kloss 1919; Rattus lalolis Tate and Archbold 1935; Rattus lanensis Kloss 1919; Rattus lontaris Chasen 1937; Rattus macmillani Hinton 1919; Rattus makassarius Sody 1941; Rattus makensis Kloss 1916; Rattus mansorius Johnson 1962; Rattus masaretes Sody 1937; Rattus mesanis Kloss 1919; Rattus mindanensis (Mearns 1905); Rattus moheius Chasen 1937; Rattus molliculus Robinson and Kloss 1922; Rattus moluccarius Sody 1933; Rattus neglectus (Jentink 1880); Rattus nemoralis (Blyth 1851); Rattus obiensis Sody 1941; Rattus ouangthomae (Milne-Edwards 1872); Rattus palelae Miller and Hollister 1921; Rattus palembang Tate and Archbold 1935; Rattus panjius Chasen 1937; Rattus pannellus (Miller 1913); Rattus pannosus (Miller 1900); Rattus pelengensis Sody 1941; Rattus pipidonis Chasen 1937; Rattus poenitentiarii (Kloss 1915); Rattus portus (Kloss 1915); Rattus povolny Niethammer and Martens 1975; Rattus pulliventer (Miller 1902); Rattus rangensis (Kloss 1916); Rattus robiginosus (Hollister 1913); Rattus robinsoni Chasen 1940; Rattus robustulus (Blyth 1859); Rattus sakisimana Tokuda 1939; Rattus samati Sody 1932; Rattus santalum Sody 1932; Rattus sapoensis Sody 1941; Rattus satarae Hinton 1918; Rattus septicus Sody 1933; Rattus shirokuma Kuroda 1953; Rattus sladeni (Anderson 1879); Rattus sumbae Sody 1930; Rattus tablasi Taylor 1934; Rattus talaudensis Sody 1941; Rattus tatkonensis Hinton 1910; Rattus thai Kloss 1917; Rattus tikos Hinton 1919; Rattus tistae Hinton 1918; Rattus toxi Sody 1941; Rattus turbidus (Miller 1913); Rattus yeni Dao 1960; Rattus yunnanensis (Anderson 1879); Rattus zamboangae (Mearns 1905) .

Distribution: Apparently indigenous to SE Asia, from E Afghanistan (Niethammer and Martens, 1975) through C and S Nepal (below about 2000 m), Bhutan, N India, N Bangladesh and NE India into S and C China (including Hainan Isl), Korea, and mainland Indochina (including offshore islands) south to Isthmus of Kra; also probably native to Mergui Arch.; not found in the Andaman Isls and most of the Nicobar Isls. Whether native or introduced to Taiwan and Japan is unknown (but see Yosida and Harada, 1985; Japanese distribution reviewed by Kaneko, 1994). Most likely introduced to the Malay Peninsula and islands on the Sunda Shelf (Medway and Yong, 1976) and nearby archipelagos just off of the Shelf, including the Mentawais (Musser and Califia, 1982; Musser and Newcomb, 1983) and Nicobar Isls (the only museum records are the holotype of pulliventer from Great Nicobar Isl described by Miller, 1902, and BMNH 20.3.1907 from Little Nicobar Isl; Musser’s identifications). Certainly introduced to the Philippines (Musser, 1977 a; Heaney et al., 1998, summarized records), Sulawesi (Musser and Holden, 1991), and numerous islands east through the Moluccas and Nusa Tenggara (Flannery, 1995 b; Musser, 1970 a, 1972, 1981 c) to W New Guinea (Flannery, 1995 a; Sody, 1941), and farther east through Micronesia to islands of Eniwetok and Fiji (Johnson, 1962 a, b), but not to the Samoas where R. rattus occurs (Yosida et al., 1985).

Conservation: IUCN – Lower Risk (lc).

Discussion: Rattus rattus species group. The authority is usually cited as 1845, but was published in 1844 (Holthuis and Sakai, 1970). The name tanezumi is the oldest for the 2n = 42 group of Asian houserats that is distinguished from the 2n = 38/40 R. rattus not only by chromosomal characters but also morphological and biochemical traits (see account of R. rattus). The probable indigenous range is generally north and east of peninsular India (judged by Musser’s study of material in AMNH, BMNH, FMNH, MZB, RMNH, USNM, and geographic distribution of karyotypes with 2n = 42; Duncan and Van Peenen, 1971; Gadi and Sharma, 1983; Markvong et al., 1973; Niethammer, 1975; Niethammer and Martens, 1975; Ray-Chaudhuri and Pathak, 1970; Raman and Sharma, 1974, 1977; Gill and Gupta, 1989; Tripathy et al., 1985; Yong, 1969; Yosida et al., 1971). In the southern portion of the Western Ghats (along SW peninsula in Karnataka and Maharashtra States) at Sagar, three individuals trapped in forest exhibited 2n = 42, and three from a nearby "domestic site" had 2n = 38. The former diploid number was attributed to R. r. wroughtoni and the latter to R. r. rufescens (Lakhotia et al., 1973; Pradhan et al., 1991), but holotypes and paratypes of wroughtoni represent R. rattus (which includes rufescens as a synonym), and the 2n = 42 sample is R. satarae (see that account). Dark-bellied populations identified as R. rattus rufescens are found occurring together with white-bellied rats in India, which prompted Tiwari et al. (1972) to recognize rufescens as a separate species, but it is simply a phenotypic morph of R. rattus found in the same populations containing the white-bellied morph (see account of R. rattus). Distributional and ecological relationships between R. rattus and R. tanezumi along the N portion of the Indian subcontinent where indigenous ranges are either parapatric or overlap still requires resolution (see discussion in Corbet and Hill, 1992).

More than one species may be present in our concept of R. tanezumi, but careful taxonomic revision using morphological, chromosomal and molecular characters will have to test such an hypothesis. Verneau et al. (1997), for example, split Vietnamese R. flavipectus from R. tanezumi because of a difference in Fundamental Numbers of karyotypes. Wang (2003) recognized yunnanensis as a separate species, but no data substantiates that treatment (see G. M. Allen, 1940, and Osgood, 1932). He also listed brunneusculus as a species with sladeni, molliculus, canna, tistae, and hainanicus as subspecies. We associate the first four taxa with R. tanezumi and hainanicus with R. andamanensis (see that account). An extensive taxonomic survey of these populations, based on a combination of DNA sequencing and morphological studies, is currently underway by K. Aplin, H. Suzuki and their various collaborators (Aplin et al., 2003 b; K. Aplin, in litt., 2004). Their preliminary analysis, using the mitochondrial cytochrome b gene, suggests that the 2n = 42 Asian group includes two distinct taxa, with a level of divergence equal to or greater that characterizes the 2n = 38 cluster. Aplin et al. (2003 b:489) summarized the fundamental division as between "... an endemic Southeast Asian taxon (recorded from Vietnam, Cambodia and southern Laos) and a northern and South Asian taxon (recorded thus far from Japan, Hong Kong, northern Vietnam, northern Laos and Bangladesh). These taxa are probably regionally sympatric in parts of Vietnam and Laos." Their work also suggests that island populations off the Sunda Shelf contain a complex admixture of both major haplotype groups, suggestive of prehistoric introductions from multiple areas with subsequent hybridization (K. Aplin, in litt., 2004). Aplin et all. (2003 c:489) suggested that "... it would be premature to speculate on the appropriate names for each of the two Asian taxa," and caution that "...the apparent extension of the north Asian taxon (which probably includes Japanese tanezumi) through to the Indian subcontinent raises the possibility that tanezumi may not be the earliest available name for this group."

Females in most populations of R. tanezumi have five pairs of mammae (one pectoral, one postaxillary, one abdominal, and two inguinal), but in some populations the postaxillary pair is twinned with the teats close together (less than 1 cm apart, usually 5 mm). This configuration is different from the six pairs of teats characterizing certain species of Rattus in the R. rattus species group (e. g., R. andamanensis) in which there are two distinct pairs of postaxillary teats, usually 1 cm or more apart. We have not seen such variation in R. rattus .

Phallic morphology of Chinese flavipectus described by Yang and Fang (1988) in context of assessing phylogenetic relationships among Chinese murines. Standard karyotype of Philippine samples described by Rickart and Musser (1993). Taxonomic, chromosomal, and ecological aspects of Chinese populations (under flavipectus) described by Zhang et al. (2000). Md Nor (1996) documented its distribution and ecology on the small islands off the northern tip of Sabah. The species does not occur on Christmas Isl or Madagascar ( R. rattus was introduced on those islands), or in the Andaman and Nicobar Isls except for Greater Nicobar Isl (see above); R. rattus from Barren Isl is the only recorded introduction of a commensal Rattus in the Andaman Isls (see account of R. andamanensis).