Greater bilby

The Pilbara is one of the few regions where bilbies still survive. They used to occur across about three-quarters of the Australian continent, including most of Western Australia, but have now contracted to the driest and least fertile parts of their former range. The known Pilbara populations are small, isolated and highly vulnerable.

Bilbies live in scattered populations of 2–3 individuals on plains with soils suitable for burrowing. In the Pilbara they tend to associate with wattle species whose root systems are inhabited by cossid moth grubs, a favoured food. They also eat other invertebrates such as spiders and termites as well as grass and sedge seeds and bulbs.

As inveterate diggers for food and shelter, bilbies earn their title as ‘ecosystem engineers’. They may build a new burrow every 2 to 3 weeks, tunnelling up to 4.5 metres, down to 3m depth, leading to burrow densities of up to 22 per square kilometre. While one bilby may regularly use more than a dozen burrows, many other species also benefit. A study in the western Kimberley found more than 40 species using bilby burrows.

The loss of bilbies has been due mainly to feral cats, foxes and altered fire regimes. In south-east and south-west Australia the last bilbies were recorded just 5–12 years after the arrival of foxes. Apart from the western deserts, the distribution of bilbies is mostly outside the distribution of foxes. The installation of artificial water sources for cattle grazing or due to mining and infrastructure development may facilitate the expansion of foxes into areas where they are currently rare. Foxes are common along the Pilbara coast and in some riparian areas but sparse in inland areas. Feral cats are likely to prey on bilbies when easier prey items become scarce, when cat densities are high or after fire. Although dingoes and dogs are known to eat bilbies, their impact has been assessed as minor and they may benefit bilbies in some areas by suppressing cat and fox activity. Bilbies show an innate antipredator response to dingoes/dogs but not to cats. Buffel grass spread is likely to be a significant threat by changing fire regimes and displacing bilby food plants.

The bilby is of great spiritual importance to Traditional Owners across its present and former range and bilby monitoring and recovery work is a strong focus of Indigenous ranger programs across central and northern Australia.