Historical record shows broad habitat use and rapid decline of the greater bilby Macrotis lagotis in eastern Australia

Abstract

Context Understanding historical distributions of species informs their ecology and response to threats, which can support management of surviving and translocated populations. Like many critical weight-range mammals in Australia, the greater bilby (Macrotis lagotis) has experienced major declines since European colonisation. The past distribution of bilbies in eastern Australia remains uncertain owing to the rapidity of their decline, their cryptic and nocturnal nature, and the paucity of specimen records. Aims We aimed to systematically collate, geo-reference and attribute bilby records from eastern Australia to better inform their historical distribution, habitat preferences, patterns of decline and response to threats. Methods We searched explorer and early settler journals, the digitised newspaper archive, interviews with long-term residents, Aboriginal language resources and ethnographies, place and property names, unpublished datasets, and documented locations of now-inactive bilby burrows. Records were geo-referenced and attributed with date, record type, source, location precision, bioregion, habitat and local abundance. The former distribution of bilby habitat in Queensland was modelled using Maxent, and the likely former occupancy of bilbies was identified using vegetation mapping. Key results More than 250 bilby records were found, only 34 of which appear in the Atlas of Living Australia. Sixty-five per cent of the records were attributed either ‘certain’ or ‘good’ reliability. Bilbies formerly occurred over most of inland New South Wales and the southern half of Queensland in areas receiving <600 mm average annual rainfall, in a wide variety of habitats. By the 1930s, bilbies were largely restricted to their current core range in south-western Queensland. This contraction in range coincided with the northward spread of rabbits and foxes. Conclusions Bilbies had a more contiguous distribution and occupied a wider range of habitats than was previously recognised. The species persisted in apparently isolated patches to the south-east, west and north of its present distribution until the 1970s, suggesting recent declines around the peripheries of its current range. By the 1990s, bilbies occupied <3% of their pre-1900 range in eastern Australia. Implications This work details changes in bilby distribution and provides key context for interpreting contemporary survey results. It also identifies areas where further surveys are required and may assist in selecting habitat for future translocations.