Rattus andamanensis Blyth 1860

Rattus andamanensis Blyth 1860, J. Asiat. Soc. Bengal, 29: 103.

Type Locality: India, Andaman Isls, South Andaman Isl.

Vernacular Names: Indochinese Forest Rat.

Synonyms: Rattus burrulus (Miller 1902); Rattus flebilis (Miller 1902); Rattus hainanicus G. M. Allen 1925; Rattus holchu Chaturvedi 1965; Rattus klumensis (Kloss 1916); Rattus koratensis Kloss 1919; Rattus kraensis (Kloss 1916); Rattus remotus (Robinson and Kloss 1914); Rattus sikkimensis Hinton 1919; Rattus yaoshanensis Shih 1930 .

Distribution: S China (Yunnan, Guangxi, Fujian, islands of Hong Kong and Hainan), Vietnam (including four coastal islands; Kuznetsov, 2000, recorded as koratensis), Laos, Cambodia, Thailand (including Koh Klum off SE Thailand in the Gulf of Siam), C and N Burma, NE India (Sikkim, N West Bengal, Arunachal Pradesh, Nagaland, Meghalaya), Bhutan, and E Nepal. Not recorded from the mainland of peninsular Thailand south of Isthmus of Kra (10EE, 30' N), but occurs on four islands (Koh Tau, Koh Phangan, Koh Samui, and Koh Kra) off the coast well south of the Isthmus (see Musser and Heaney, 1985). Also on the Andaman Isls (islands of North Andaman, Interview, Middle Andaman, Long, Henry Lawrence, Havelock, South Andaman, and Little Andaman) and Car Nicobar, northernmost of the Nicobar Isls. Limits in NE India and Nepal unresolved. Distribution based on specimens examined by Musser).

Conservation: IUCN – Vulnerable as R. sikkimensis .

Discussion: Rattus rattus species group. Usually listed as sikkimensis, which was described as a subspecies of R. rattus (Hinton, 1919 a), then arranged as a synonym of R. r. brunneusculus (Ellerman, 1961), later identified as R. sikkimensis (Musser and Newcomb, 1983; Musser and Heaney, 1985; Musser and Carleton, 1993), and discussed under R. remotus by Corbet and Hill (1992), who noted that remotus is an older name than sikkimensis . South Vietnamese samples have also been described under R. sladeni (Van Peenen et al., 1969), N Vietnamese series as R. koratensis (Dao, 1985), and Thai samples under R. koratensis and R. remotus (J. T. Marshall, Jr., 1977 a) .

The oldest name for the species is andamanensis, which Musser and Lunde (ms) determined by study of the holotype and large series (in USNM, KNMB, and ZSI) collected on the Andaman Isls. A multivariate analysis of morphometric traits has verified that the Andaman Isls populations and those on mainland Indochina are the same species (Musser and Lunde, ms). Corbet and Hill (1992:344) included macmillani (Hinton, 1919) as a synonym with question, but the holotype is an example of Rattus tanezumi (Musser’s study of the holotype at BMNH). Those authors also listed klumensis and kraensis in the synonymy of R. rattus, but the respective holotypes represent R. andamanensis (Musser’s study of holotypes and other specimens). Shih’s (1930) yaoshanensis from Guangzi Province of S China was described as a subspecies of Niviventer confucianus and is listed that way by Corbet and Hill (1992), but the holotype (which Musser has not examined) is too large for confucianus as are its cranial and dental dimensions; measurement values and pelage coloration fall within the range of morphological variation exhibited by Chinese samples of R. andamanensis (a young adult from the type series sent to AMNH is an example of R. andamanensis). A sample from Car Nicobar was described as R. rattus holchu by Chaturvedi (1965), but Miller (1902) had already described burrulus from the same island (thought to be conspecific with R. burrus by Corbet and Hill, 1992; see that account), and all are examples of R. andamanensis (Musser’s study of the respective holotypes and other specimens). While R. andamanensis is sympatric with R. tanezumi on mainland Indochina and many offshore islands in the South China Sea, it and R. palmarum are the only Rattus found on Car Nicobar, and R. andamanensis occurs with R. stoicus on the Andaman Isls from which R. tanezumi is absent (a sample from Barren Isl in the Andamans described as atratus by Miller [1902] and two [BMNH 10.7.26.2 and 10.7.26.3] from South Brother Isl, northeast of Little Andaman Isl, represent introduced R. rattus; Musser’s study of holotype of atratus in USNM, and BMNH specimens). Holotypes tied to the synonyms for R. andamanensis document a large-bodied species of Rattus with rich brown upperparts, white underparts, long tail relative to head and body length, 12 teats, robust skull, small bullae, and large molars. Chromosomal comparisons between R. andamanensis (reported as koratensis) and other species of Rattus from S Vietnam reported by Baskevich and Kuznetsov (1998).