Thinking outside the fox? New study suggests baiting could reduce attacks

Researchers in a recently released study have found that giving foxes drugged food may help to reduce the number of attacks on livestock and native wildlife in the long term.

One of the researchers, PhD candidate at the Fenner School of Environment and Society at the Australian National University (ANU), Tim Andrewartha, said the study used a method named CTA.

“CTA is where if you put a food source that will make the animal wildly ill, it will actually associate that as a cue of the illness itself,” he said.

Between March and June 2019, the researchers placed baits at the Wandiyali-Environa Wildlife Sanctuary, near Canberra.

Passive infrared cameras watched the 30 bait stations, which were buried five to 10 centimetres underground, and a new bait was placed at each site every two days.

“We want to use this tactic, eventually, to protect native species, but we don’t want to put native species at risk,” Mr Andrewartha said.

“These baits were chosen to be a sort of proxy for the predation of animals.”

Some baits contained a capsule with levamisole, a chemical that introduces nausea and/or diarrhea in the foxes, but no long-term side effects.

Other baits were served with an empty gelatin capsule, and were the control for the study.

Mr Andrewartha said the study’s goal was to see if CTA would affect fox behaviour.

“In terms of this study, what we were doing is we were seeing if the use of buried baits in the Australian context would be successful,” he said.

“There had been some testing in Australia using chicken carcasses before, but it did not produce successful results, so we wanted to show that this was a successful tactic of reducing consumption of baits.”

Over three periods, untreated baits were laid, followed by levamisole-containing baits and untreated baits again.

During the study, 750 baits were distributed, of which 210 contained levamisole.

During the final period, baits taken fell by 30 per cent, with researchers arguing that foxes had eaten the levamisole-containing baits, became ill, and were hesitant to risk sickness despite the later absence of levamisole.

Mr Andrewartha said the study had shown the usefulness of CTA in red foxes, though future studies on the topic were needed.

“From reading the literature, I had absolute faith in the tactic, but when you’re out there putting out the baits, you wonder how impactful this will be on a large-scale level,” he said.

“We were really pleased with the level of impact we got in the study.

“It was a really, really great surrogate for the potential of the tactic in the future.”

There were also benefits to adopting strategies that focused on changing foxes’ behaviour, Mr Andrewartha said.

“There’s been research to show that the presence of foxes in the landscape will actually keep rabbit populations in control, as that’s one of their primary food sources.

“On top of that, a low level of predation has also been shown to maximise fitness, so it’s about removing the maladaptive individuals that are not able to survive the presence of foxes from the population, allowing improvement of evolutionary fitness over time.”

Ideally, the CTA technique would come to be used alongside other methods, both lethal and non-lethal, he said.

“The more different tactics available in farmers’ and land managers’ arsenal, the greater potential they have to get that predation rate of foxes down to zero.”

Mr Andrewartha said tactics had often focused on controlling or limiting fox populations in Australia.

“While population management has been really effective, foxes are very difficult to manage and persist at quite high management,” he said.

“The impact of migration can also reduce the effectiveness of management techniques over the course of a year.”

The study was led by the ANU in collaboration with the University of South Australia, the University of Tokyo and the James Hutton Institute in Scotland.