Rattus nitidus Hodgson 1845

Rattus nitidus Hodgson 1845, Ann. Mag. Nat. Hist., ser. 1, 15: 267.

Type Locality: Nepal.

Vernacular Names: White-footed Indochinese Rat.

Synonyms: Rattus aequicaudalus (Hodgson 1849); Rattus guhai (Nath 1952); Rattus horeites (Hodgson 1845); Rattus manuselae Thomas 1920; Rattus obsoletus Hinton 1919; Rattus rahengis Kloss 1919; Rattus ruber (Jentink 1880); Rattus rubricosa (Anderson 1879); Rattus subditivus Miller and Hollister 1921; Rattus vanheurni Sody 1933.

Distribution: Mainland Southeast Asia from S China (SE Xixang, Yunnan, Sichuan, Guizhou, Hunna, Guangxi, Guangdong, Fujian, Jiangxi, Zhejiang, Shanghai, Jiangsu, Anhui, S Shaanxi, SE Gansu, and Hainan Isl; Wang, 2003), Vietnam (including the coastal islands of Cat Ba and Thô Chu; Kuznetsov, 2000), Laos, N Thailand, Burma, Bangladesh, Nepal, Bhutan, and N India (Uttar Pradesh, Sikkim, West Bengal, Arunachal Pradesh, Meghalaya, Tripura, Mizoram, and Manipur; Agrawal, 2000); this distribution probably represents the indigenous range (Musser and Holden, 1991). Records east of the continental shelf are from C Sulawesi, Luzon Isl in the Philippines (recorded only from Benguet Province, Heaney et al., 1998; Musser, 1977 a; Musser and Holden, 1991), Pulau Seram in the Moluccas, the Vogelkop Peninsula of the Prov. of Papua (= Irian Jaya), and the Palau Isls (east of the Philippines; Barbehenn, 1974); this distribution likely represents introductions mediated by human agency (Musser and Holden, 1991).

Conservation: IUCN – Lower Risk (lc).

Discussion: Rattus norvegicus species group. Association of synonyms documented by Corbet and Hill (1992), Ellerman (1941), Khajuria et al. (1977), J. T. Marshall, Jr. (1977 a, b), Musser (1981 c), Musser and Holden (1991), and Taylor et al. (1982). Phallic morphology described by Yang and Fang (1988) in context of assessing phylogenetic relationships among Chinese murines. Yang et al. (1994) and Zeng et al. (1996 a, b, 1999) reported various aspects of population ecology for Chinese populations, which are among the few studies of this kind covering R. nitidus. In pristine environments, R. nitidus lives in forested habitats along streams and readily enters water (field observations by G. Musser and D. Lunde in N Vietnam), which may account for its dense pelage resembling that of R. norvegicus, also a forager in streams and lakes. The names manuselae (Seram), ruber and vanheurni (Vogelkop Peninsula), and subditivus (Sulawesi) were applied to specimens thought to represent native species (Musser, 1877 a; Musser and Holden, 1991).

Analyses of DNA sequences from L1 (LINE-1) elements identified a specimen of Rattus from Pulau Seram (Gunung Binaiya) in the Malukus as R. rattus moluccarius (Usdin et al., 1995) or R. cf. moluccarius (Verneau et al., 1997, 1998) that has close molecular similarities to R. norvegicus. However, the holotype and type series of moluccarius is from nearby Pulau Buru and represent a large-bodied population of R. tanezumi (Musser, 1970 a, discussed under R. rattus). The voucher specimen (not examined by us) is probably an example of R. nitidus, which occurs on Seram "... in many habitat types over a broad altitudinal range" (Helgen, 2003 b:170). The type series of manuselae, for example, was collected at 1830 m, and Helgen (2003 b) listed samples taken from 350 m to 1830 m; R. norvegicus has not been recorded from Seram, and if it has been introduced there would likely be restricted to port towns (see account of R. norvegicus).

The phylogenetic association of R. nitidus with R. norvegicus indicated by DNA sequences from L1 elements is substantiated by recent analyses of mtDNA cytochrome b sequences, which aligns samples of R. nitidus (and R. pyctoris; see account) with R. norvegicus (K. Aplin, in litt., 2004). Morphology also supports this alliance. Both R. nitidus and R. norvegicus have dense and soft fur, six pairs of teats, and an upper M 1 in which the anterolabial cusp (t3) on the anterior lamina is missing or undetectable due to its coalesence with the adjacent central cusp.