Possum extinctions at the marsupial frontier: the status of the northern common cuscus Phalanger orientalis on Santa Ana Island, Makira Province, Solomon Islands.

Abstract

ON zoogeographic maps, the Solomon Islands are shown as the north-eastern limit of Australidelphian marsupial distribution in Australasia. This distinction is due to the presence of a single New Guinean marsupial, the northern common cuscus Phalanger orientalis, which was probably introduced via the Bismarck Archipelago by prehistoric human agency (Flannery 1995; Spriggs 1997; Heinsohn 1998; Wickler 2001). P. orientalis is found across most of the principal Solomon Islands, with the exception of the remote far-eastern oceanic islands of Santa Cruz (Temotu) Province. In the scientific literature, the exact eastern limit of distribution for P. orientalis is generally given as San Cristobal (Makira) Island in Makira Province (Laurie and Hill 1954; Flannery 1995), the eastern most peninsula of which extends to 162° 23' E. The next landmass to the east is the small 5 km diameter and 143 m high limestone atoll of Santa Ana (Owa Rafa) which lies across a 7.5 km open water crossing.