Media release

From: The University of Melbourne

Conservation programs that control foxes in order to protect Victoria’s endangered and threatened native animals may be inadvertently giving space for feral cats to thrive, according to research by the University of Melbourne.

In a paper published in Oikos, wildlife ecologist Dr Matthew Rees and a team from the University and the Conservation Ecology Centre found that cats in dry forests shifted to hunting at night when foxes were controlled, potentially giving them access to more nocturnal native mammals.

This latest research follows findings by the team published in the Journal of Applied Ecology that density of feral cats increased in the Otway Ranges rainforests after foxes were removed, and that feral cat densities in the Glenelg region in southwest Victoria were often higher in forests with long-term fox control than those without.

“Together, these two papers paint a picture of the uneasy balance that exists between foxes and feral cats. These introduced predators are everywhere in Victoria, even remote rainforest gullies. They share many of the same prey and have caused catastrophic damage to our wildlife,” lead author Dr Rees said.

“Our research shows that foxes might influence feral cat behaviour, including where and when cats hunt, and which animals they attack. We found that cats and foxes often share the same spot in the forest, but that cats come out at different times of the day depending on whether foxes are more or less active.”

“Victoria’s fox management programs are essential to protect some of our most vulnerable wildlife. However, it is also important we keep an eye on whether feral cats become more abundant or bolder following fox control,” said Dr Bronwyn Hradsky, who supervised this research.

Dr Hradsky said researchers had wanted to understand why some native species, such long-nosed potoroos, bounced back in forests after long-term fox control, while others such as southern brown bandicoots saw little improvement.

To find out how broad-scale fox baiting programs for conservation affect both pest and native animals, University researchers and state government land managers repeatedly put out survey cameras at 1232 sites across two forest regions in southwest Victoria.

They then painstakingly reviewed and tagged millions of photographs of wildlife, and identified individual cats based on their unique coat patterns.

The data showed that that feral cat population densities were often higher where foxes were baited, with the difference ranging from only a slight increase to 3.7 times higher.

Foxes have been controlled to protect native wildlife for decades in some regions of Victoria. In contrast, feral cats were only declared an established pest species on Victorian crown land in 2018, and broadscale feral cat control programs in Victoria are currently very limited, said Dr Rees.

Foxes and feral cats are estimated to jointly kill 2.6 billion mammals, birds and reptiles across Australia each year, according to 2022 research by ecologists including Dr Rees. These estimates, however, are highly dependent on how many foxes and cats there actually are.

Dr Rees’ research shows that the impacts of cats in wet forests are likely higher than first thought: he recorded approximately one feral cat per square kilometre in the dense wet forests of the Otways – the highest recorded for native forest on the mainland. In contrast, there was only about 0.3 cats per square kilometre in dry forests of southwest Victoria, although cat numbers were twice as high in some forests where foxes were controlled.

“While more research needs to be done, land managers are likely to face a difficult job balancing the benefits of pest control with potential unintended consequences. In forests where both foxes and feral cats are abundant, we need to think of ways to protect native wildlife from both predators at the same time.” Dr Rees said.