THE BILBY MACROTIS LAGOTIS (MARSUPIALIA PERAMELIDAE) IN SOUTH-WESTERN AUSTRALIA ORIGINAL RANGE LIMITS, SUBSEQUENT DECLINE, AND PRESUMED REGIONAL EXTINCTION

WA Museum Records and Supplements | Updated 1 decade ago

Abstract - Knowledge of the original south-western geographic range limits of the Bilby Macrotis [agotis in Western Australia, before its regional decline and apparent extinction, is currently underpinned by only six museum records, including three from near Bridgetown. The collector of one of the latter specimens in 1933 was interviewed, clarifying the source localities of these specimens. A further 155 residents, mostly aged 70 years or more, were interviewed, resulting in additional localities based on observations. A search  of published and unpublished historical sources also revealed several acceptable records. This information was then coupled with detailed 1: 250 000 vegetation complex maps prepared in 1998 for the Regional Forest Agreement to produce a map of the inferred original distribution of the Bilby in south-western Australia. Bilbies appear to have occurred in suitable areas of open forest and woodland in the northern and eastern jarrah forests, west to about Chittering, Chidlow, Marradong, Bowelling, Boyup Brook and Bridgetown. The main southern limit appears to have been Warren River at Quillben forest block (along valleys containing sandy soils), Perup River near Deeside, Hay River near Forest Hill, and north of Porongurup Range. Bilbies also occurred, apparently sporadically, farther southwest at Margaret River, along the Blackwood River between Darradup and Alexandra Bridge, near Lake Jasper, near Dombakup, and between Kent River and Denmark.

Factors possibly implicated in the local extinction of the Bilby in southwestern Australia are reviewed. Although drought, disease, trapping, and distribution of poison baits for rabbit control reduced population numbers of the Bilby, the coup de grace was delivered by the arrival of the Fox in the late 1920s/early 1930s. The last specimens were collected in 1935, though a few populations might have persisted very locally until the 1970s or even 1980s. Current proposals to re-introduce the Bilby to public land in its inferred former range will serve to test the hypothetical original distribution of the Bilby, prior to the arrival and establishment of the Fox.