Rattus burrus Miller 1902

Rattus burrus Miller 1902, Proc. U. S. Natl. Mus ., 24: 768.

Type Locality: India, Nicobar Isls, Trinkat Isl.

Vernacular Names: Nicobar Archipelago Rat.

Synonyms: Rattus burrescens (Miller 1902) .

Distribution: Islands of Trinkat, Little Nicobar, and Great Nicobar in the Nicobar Arch.; apparently absent from Car Nicobar, northernmost of the Nicobar Isls, which is inhabited by populations of R. andamanensis and R. palmarum (see those accounts).

Conservation: IUCN – Vulnerable.

Discussion: Rattus rattus species group. Recent morphometric analyses indicate R. burrus to be most closely related to R. simalurensis from the Simalur Arch., R. lugens from the Mentawai Arch., and R. adustus from Pulau Enggano. Except for larger body size, morphology of the four species resembles that characterizing the R. tiomanicus complex from the Sunda Shelf (Musser, 1986; Musser, ms.). Rattus burrus is also morphologically similar to R. palmarum from Car Nicobar, the northernmost of the Nicobar Isls (see that account), but differs in being smaller in body size (e. g., greatest skull length = 41.3-46.7 mm for 12 adult R. burrus, 49.0-54.0 mm for three adult R. palmarum), with softer pelage. Whether burrus is a separate species or simply a smaller-bodied insular variant of the larger-bodied and coarse-furred R. palmarum warrants careful study. Both taxa may be Nicobar endemics, but their status will have to be tested by a systematic revision of the R. tiomanicus complex. Corbet and Hill (1992) questionably included burrus and burrescens as synonyms of R. tiomanicus and regarded burrulus, which we treat as a synonym of R. andamanensis (see that account), as possibly conspecific with burrus . No other species of native Rattus is sympatric with R. burrus, but examples of R. tanezumi have been collected from Great Nicobar (holotype of pulliventer Miller, 1902) and Little Nicobar (BMNH 20.3.1907) Isls, and R. rattus is documented from Nancowry Isl (USNM 111800); both species were introduced.