Exposing vulnerable species like the bilby to an environment with predators before releasing them into the wild could help improve the species’ ultimate survival, new research by UNSW ecologists has shown.
In a study—published in the Journal of Applied Ecology—ecologists compared the behaviour and subsequent survival of two groups of bilbies: one that had been deliberately exposed to feral cats, and one that had not come into contact with predators before.
The study is the first experimental test of predator exposure that shows how the fate of animals that are introduced into a predator‐rich environment could be improved by prior experience living with predators.
The team— from UNSW, Arid Recovery and UCLA—conducted the experiment in the Arid Recovery Reserve, a 123 square kilometre network of fenced exclosures in arid South Australia. Several locally extinct species have recently been re‐introduced into the reserve, including the vulnerable greater bilby.
“The reserve is divided into paddocks, and we conducted the experiment in three paddocks: the predator‐free paddock, the predator‐exposed paddock, and the release site,” lead author Aly Ross said.
Bilbies from the predator-exposed paddock had been living with five feral cats in the two years leading up to the experiment, while bilbies from the predator-free environment had never encountered cats or other predators.
“First, we compared the behaviour of bilbies from the predator‐free and predator‐exposed populations in a small fenced pen of a bit over 50 square metres—primarily to see how they’d react to a new environment,” Ross said.
The team found that the behaviour of the animals that had previous predator exposure differed from the predator ‘novices’.
“Animals that had lived in an environment with predators moved less and sought cover more quickly,” Ross said.
“This shows that they were warier of potential threats, whereas the predator-free group of bilbies showed fewer signs of predator awareness.”
The fact that animal behaviour can be changed by predator training has been demonstrated before. It’s what the group found next that is particularly interesting.
“In a second experiment, we released bilbies from the predator-exposed paddock and some from the predator-free paddock into a third paddock with some feral cats,” Ross said.
“Unfortunately, we found that 71 per cent of the predator‐free bilbies died in the week after release, but only 33 per cent of the predator‐exposed bilbies met the same fate—showing that the bilbies who had been exposed to the very real threat of predators already had benefitted from that experience.”
The findings have important implications for the conservation of native animals and programs that seek to reintroduce species like the bilby.