Bilbies may not be as naïve to feral cats as previously thought, well not in the West Kimberley where a study determined that Australia’s long eared marsupial will limit its burrowing behaviour following a visit by a feline predator.
Faith Sze-En Chen, a master’s student at Murdoch University, set out in 2021 to discover whether bilbies, which are classified as level one prey naivety species, would alter their burrowing behaviour in response to a feral predator. In other words, have they developed any predator awareness since cats were introduced to Australia in the 1800s. As a level one prey naïve species, they show no recognition of the predator as a risk while at level two, the native species recognises the predator but adopts the wrong anti-predator response and at level three, the species recognises danger and has an appropriate response.
Faith also hoped to learn whether illumination from a full moon will increase feral cat activity and increase their visits to Bilby burrows.
To answer her burning questions, Faith selected five known Bilby ‘loping’ grounds to set up camera traps and monitor both their behaviour and feral cat activity. These were a wild population in the West Kimberley region and feral predator-free fenced populations at Australian Wildlife Conservancy’s (AWC) Mt Gibson Wildlife Sanctuary in the WA Wheatbelt, Barna Mia Native Animal Sanctuary and Kanyana Wildlife Rehabilitation Centre. Yawaru, Nyikina-Mangala, Nana, Kallamaya, Wiilman, Badimia and Whadjuk Noongar are the traditional owners on whose land this project was conducted.
As a level one prey naivety species, all five Bilby populations were expected to show no recognition of predation risk and no anti-predator behaviour. But what Faith found in the West Kimberley was not as expected.
While reviewing camera trap footage, Faith discovered that in the absence of a feral cat, West Kimberley bilbies spent roughly 15% of their time performing burrow maintenance – this included digging and clearing away soil or debris from the mouth of their burrow. In the five days following a feral cat visit, this important Bilby behaviour decreased to 5% and increased again seven days after a cat visit.
A thrilled Faith said that these results indicate that the wild West Kimberley population has developed, ever so mildly, a level of predator awareness.
“As ecosystem engineers, we understand that Bilby burrowing behaviour plays a significant role in shaping the ecology of Australian ecosystems by turning over soil, modifying the physical environment and creating habitat for other species,” Faith explained. “However, the noise created from digging compromises bilbies’ ability to assess predation risk and attract unwanted attention.”
“Entering this research project, I hypothesised that bilbies would avoid their burrows and decrease vulnerable activity after a visit by a feral cat,” Faith explained. “While there was no evidence that they avoided their burrows in the presence of a feral cat, we found that bilbies decreased burrowing activity – this was particularly exciting because this reduced their susceptibility to predation.”
During her research, Faith also found that feral cat activity increased on a full moon and visits to Bilby burrows doubled compared to nights with a new moon.
“While humans love and embrace this monthly lunar effect, this extra moon illumination leaves our native species, particularly the Bilby, more vulnerable at their burrows.
The bilbies at Mt Gibson Wildlife Sanctuary, along with eight other reintroduced species, are protected by a 7,838 hectare feral predator-free fenced area – the largest cat and fox-free area on mainland WA. This protective environment enabled Faith to use the sanctuary as a comparison site to a wild population in the West Kimberley.
Through camera trap footage, Faith learned that Mt Gibson bilbies are an active population, using 10% of their time to conduct maintenance on their burrows. This was just short of the West Kimberley population which spends nearly 20% of their time maintaining their burrows.
Faith also found a significant difference across all populations in the time of night that bilbies would conduct their burrow maintenance. Mt Gibson’s population was consistent with their efforts, caring for their burrows throughout the night. On the other hand, bilbies at Kanyana started their burrowing early in the night while the West Kimberley and Barnia Mia groups waited until closer to sunrise.
This project is supported by NACC NRM through funding from the Australian Government’s National Landcare Program.
To learn more about the Bilby population at Mt Gibson, click here.
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