Rattus tanezumi, Temminck, 1844

Dinets, Vladimir & Asada, Keishu, 2021, Noble savages: human-independent Rattus rats in Japan, Journal of Natural History 54 (37 - 38), pp. 2391-2414 : 2392

Rattus tanezumi

‘Eastern’ black (or Asian/Oriental house) rat Rattus tanezumi Temminck, 1844 , originally described from Japan, is closely related to R. rattus sensu stricto, but is usually considered a full species, although such treatment renders one or both of the taxa polyphyletic ( Aplin et al. 2011) and the two forms can hybridise ( Lack et al. 2012; Conroy et al. 2013), in Japan among other locations ( Chinen et al. 2005). In this article we discuss only R. tanezumi sensu stricto (Lineage II in Aplin et al. 2011), hereafter Rt. Introduced throughout the Oriental region and locally elsewhere ( Burgin 2017c), Rt is thought to originate from Yunnan and northern Indochina, where its genetic diversity is the highest among mainland populations ( Guo et al. 2019) The earliest fossils are from Early Pleistocene cave deposits of Thailand ( Chaimanee and Jaeger 2001); in Korea it is known from the Middle and Late Pleistocene ( Yeong-Seok 2015) while in central China it does not appear until the Late Pleistocene ( Zheng 1993); in all three cases the fossils were identified as R. rattus sensu lato, but likely belong to Rt based on geography. In Japan the earliest (Middle Pleistocene) fossils possibly of this taxon are from Honshu, where they predate the human arrival; there are also Late Pleistocene and Holocene fossils assigned to R. rattus sensu lato from Honshu and Kyushu ( Kawamura 1989; Iwasa 2015c). The fossil record shows Rt to be an ancient introduction in the central and southern Ryukyu Islands, where it was not present prior to the human arrival ( Kowalsky and Hasegawa 1976; Otsuka and Takahashi 2000). In historic times Rt has been introduced to many other islands, including Hokkaido in the twentieth century ( Ota 1968) and the remote Ogasawara Islands ( Kambe et al. 2011).

Rt occurs in human settlements and agricultural areas (its scientific name tanezumi means ‘ricefield rat’ in Japanese), but also in forests on all main islands of Japan except Hokkaido, and on many smaller islands where it is often the most abundant non-volant forest mammal (see Results). However, Rt in Japan has only been studied in urban and agricultural habitats, with the exception of very cursory studies of forest populations in southern Ryukyu Islands (see bibliography in Iwasa 2015c).