Rattus pyctoris Hodgson 1845

Rattus pyctoris Hodgson 1845

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

Type Locality: Nepal.

Vernacular Names: Himalayan Rat.

Synonyms: Rattus celsus G. M. Allen 1926; Rattus gilgitianus Akhtar 1959; Rattus khumbuensis Biswas and Khajuria 1955; Rattus rattoides (Hodgson 1845); Rattus shigarus (Miller 1913); Rattus turkestanicus (Satunin 1903); Rattus vicerex (Bonhote 1903).

Distribution: Mountains of SE Kazakhstan, Kyrgyzstan, E Uzbekistan, and Tajikistan (Kucheruk, 2000); EC Iran (NE Kerman Province; FMNH series); N Afghanistan (Hassinger, 1973; Niethammer and Martens, 1975; BMNH and FMNH specimens); N Pakistan (Akhtar, 1959; USNM material); N India (Agrawal, 2000; large series in BMNH, FMNH, and USNM); Nepal (Ellerman, 1961; Niethammer and Martens, 1975; BMNH, FMNH, and USNM specimens); and S China (Yunnan, Sichuan, and Guangdong; AMNH and FMNH material).

Conservation: IUCN – Lower Risk (lc) as R. turkestanicus.

Discussion: Rattus norvegicus species group. Despite past use of rattoides Hodgson, 1845 (Caldarini et al., 1989; Corbet, 1978 c; Ellerman, 1961; Ellerman and Morrison-Scott, 1951), it is preoccupied by rattoides Pictet and Pictet, 1844, a synonym of R. rattus (Schlitter and Thonglongya, 1971). The name turkestanicus (type-locality = Kyrgyzstan, Oshskaya Obl., Lenniskii p-h, Arslanbob) has generally replaced rattoides (Corbet and Hill, 1992; Musser and Carleton, 1993; Musser and Newcomb, 1985; Niethammer and Martens, 1975) for the species but should be abandoned for pyctoris, which is the oldest name (Musser and Carleton, 1993). Hodgson’s (1845) pyctoris has historically been treated as a synonym of either R. rattus (Ellerman, 1941) or R. nitidus (Corbet, 1978 c; Ellerman, 1961; Ellerman and Morrison-Scott, 1951). Musser studied the holotype of pyctoris (BMNH 45.1.8.381), the skin and skull of a young adult. The skin is in poor condition, and posterior part of the cranium and posterior portions of the dentaries are missing. However, the skin is sufficiently intact to determine that the fur is shaggy and brown over the upperparts, in contrast to R. nitidus, which has dark grayish brown upperparts and dense, soft pelage. The rostrum is wide and short (narrow and slender in R. nitidus), molars are chunky and wide (thinner and gracile in R. nitidus), and cusp t3, although small, is present on M1 (missing or so coalesced with cusp t2 that it is usually undetectable). Musser found the holotype of pyctoris to closely resemble the holotype of Hodgson’s rattoides and to be inseparable from BMNH Nepalese specimens usually identified as either rattoides or turkestanicus.

Three distinctive morphological, chromosomal, and geographic forms are included under R. turkestanicus (Caldarini et al., 1989; Capanna and Corti, 1991; Niethammer and Martens, 1975) and were first recognized by Hinton (1922), who treated all as species (R. turkestanicus, R. vicerex, and R. rattoides) but also suggested that each may instead be a well-differentiated subspecies. Subsequently, R. turkestanicus and R. vicerex were reported to occur sympatrically in Jammu and Kashmir regions of NW India (Chakraborty, 1983; Agrawal, 2000). The latter is said to be distinguished from R. turkestanicus by its shorter tail (shorter than head and body, conspicuously longer in R. turkestanicus) and fewer teats (four pairs versus six pairs in R. turkestanicus); most of the specimens are young and their identification as a species separate from R. turkestanicus has to be verified within the framework of a careful systematic treatment (Musser could not distinguish two species in the large series from N India and N Pakistan examined at BMNH and USNM). Such an inquiry should also examine significance of variation in pelage coloration (Agrawal, 2000; Corbet and Hill, 1992; our study) and chromosomal morphology (see above) among geographic samples, and determine whether the three groups represent separate species or geographic variants.

Distribution of R. pyctoris according to habitat types in SE Kazakhstan documented by Kucheruk (2000, as R. turkestanicus), who also described habitat interaction between that species and R. norvegicus and R. rattus. In contrast to those two, populations of R. pyctoris are less dependent upon anthropogenic habitats and its natural range has not been enlarged by following human settlement. Comparisons among R. pyctoris, R. norvegicus, and R. rattus in mandible shape and its potential taxonomic significance documented by Lapshov (1992, as turkestanicus). Russian range, taxonomy, and other characteristics reviewed by Gromov and Erbajeva (1995, as turkestanicus).

Including R. pyctoris in the same clade as R. norvegicus and R. nitidus is based primarily upon recent analyses of mtDNA cytochrome b sequences (K. Aplin, in litt., 2004). Rattus pyctoris has shaggy, dense fur and six pairs of teats, traits also characterizing R. norvegicus. The M1 of R. pyctoris also has a reduced anterolabial cusp (t3) relative to the adjacent two cusps forming the anterior lamina; cusp t3 is usually absent or undetectable in most examples of R. norvegicus and R. nitidus, but prominent in all other species of Rattus.