Study cautions against total rabbit removal

RABBITS have a long and notorious association with the Geelong region, but a new study from Deakin University suggests removing them all could be bad for Australia’s native species.

The study, published recently in the Journal of Applied Ecology, found that introduced rabbits were negatively affecting native species through competition for food and shelter, and supporting larger cat and fox populations.

However, if lots of rabbits are removed quickly, numbers of small native mammals could decline in the short-term.

Deakin Associate Professor of Wildlife Ecology Euan Ritchie, alongside colleagues from the University of Adelaide and France’s CNRS, used simulation models to evaluate the effects on a mammal food web of reducing rabbit populations to varying degrees.

The modelling allowed researchers to examine how changes in rabbit numbers would impact a typical mammal community from arid Australia, including their effect on cats, foxes, dingoes, kangaroos and small native mammals.

Researchers found the removal of rabbits could benefit native biodiversity immediately at removal rates between 30 and 40 per cent. However, if increased beyond these levels, numbers of small native mammals would initially decline.

“The results we found provide insight into potential consequences for mammal communities resulting from rabbit control, especially where rabbit population control is substantial,” Associate Professor Ritchie said.

“It shows the importance of considering and accounting for multiple species, and their interactions, as part of pest control and wildlife management.” Importantly, researchers found that native mammal abundance recovered and increased after a time delay, with small mammals benefitting from sustained rabbit control.

Associate Professor Ritchie said higher rates of rabbit control could initially reduce native mammal numbers for two reasons.

“Kangaroo numbers increase over the rabbit control period and they then may compete with smaller native mammals for food, but through grazing may also reduce vegetation cover, potentially exposing small mammals to increased predation risk.

“There is also an increase of predation by cats over the rabbit control period, as they are presumably forced to switch from predominantly hunting rabbits to increasingly hunting small native mammals.”