Bilbies are not only beautiful, but literally bring life to the desert with their digging.
How we’re helping
Since we first released greater bilbies (Macrotis lagotis) into the Reserve in 2000, it is estimated that their population has grown to between 800 and 1500. In 2004 we attempted to release bilbies outside the fence, accompanied with predator control. We also tried to train bilbies to become more predator savvy, by chasing them with model cats. These efforts were unsuccessful.
UNSW, in collaboration with Arid Recovery, has developed a project to try and improve the anti-predator responses of the greater bilby to cats and foxes. The project has seen positive results already, with bilbies being able to survive and breed while living alongside low densities of cats in one of Arid Recoveries experimental enclosures.
Bilbies as 'Eco-Engineers'
Bilby diggings restore the soil and regrowth of the vegetation. By creating deep holes in the sand, they enable plant material to fall and decompose. Each bilby creates numerous compost pits every night. These become high in carbon and nitrogen – an important nutrient for the growth of plants and the germination of seeds.
Where they’re foundThe greater bilby was once found on 70% of Australia’s mainland, but now occupies just 20% of its former range. Scattered populations remain in the Tanami, Gibson and Great Sandy Deserts, as well as the Pilbara and Kimberley regions, and the Mitchell grasslands in Southwest Queensland. They have also been reintroduced to a few protected sites across Australia.
Bilbies construct spiral-shaped burrows which can be up to three meters long and two meters deep. The entrance to a bilby burrow is often under a small shrub, and at Arid Recovery is usually left open. At other sites, bilbies often backfill their burrow entrance, possibly to protect it from predators or to regulate temperatures. Bilbies frequently dig new burrows and visit up to ten per night.
Bilbies have an excellent sense of smell and hearing, which they use to find food. They can detect food a metre underground and use their long sticky tongue to lick up seeds and insects. This causes bilbies to ingest a lot of sand during foraging – meaning 20–90% of their faeces may be composed of sand!
Bilbies breed year-round and have a gestation period of 12 – 14 days. The joeys spend the first 80 days of their lives in from their mother’s pouch. Two weeks after emerging the pouch, young bilbies become independent. The pouch is backward opening, so when the mother bilby digs, the pouch does not fill with sand.
The rapid decline in the bilby’s range is largely due to feral cats and foxes. Grazing by rabbits and livestock, the fragmentation of habitat by land clearing, and changed fire regimes have also contributed. Now classified nationally as vulnerable, the fate of the greater bilby is hanging in the balance. A relative of the greater bilby, the lesser bilby is now completely extinct. Just 100 years ago, it was considered to be common.
A Greater Bilby renovating it’s burrow at night. Filmed by Hugh McGregor.