Poison baits were used on 1,400 feral cats, foxes and dingoes. We studied their fate to see what works
- Written by Pat Taggart, Adjunct Fellow in Ecology, University of Adelaide
Poisoned baits are the main way land managers control foxes, feral cats and dingoes. Baiting is done to reduce livestock and economic losses, or pressure on endangered wildlife.
Millions of baits are laid annually. But we still don’t understand how effective baiting actually is. Current evidence paints a mixed picture. That’s a problem, because baiting can have unintended consequences, such as killing native animals we don’t want to target. Some research suggests baiting can actually increase attacks on livestock, or that poisoning dingoes can increase feral cat and fox numbers and worsen the damage to native wildlife.
We need better evidence on what baiting does and doesn’t do. Our new research draws on data from 34 previous studies assessing baiting effectiveness. In total, these largely Australian studies summarised the fate of more than 1,400 cats, foxes and dingoes. We used these data sets to conduct the most comprehensive analysis of baiting effectiveness to date.
Baiting is ubiquitous
Baits can be purchased commercially or produced in-house. In some states, land managers can bring meat baits to government authorities to have poison added free of charge. They are then distributed by vehicle along tracks and roads or dropped from aircraft across vast areas of Australia, New Zealand and islands worldwide.
Single baiting programs can sometimes cover areas larger than 9,000 square kilometres – a land area similar to Puerto Rico or Cyprus.
So how can we best undertake these baiting programs?
1. Baiting does work
Across the 34 studies, baiting cut predator survival in half (51.7%) – substantially higher than the death rate in unbaited areas (16%).
This finding was broadly consistent regardless of whether baits were placed along tracks and roads or scattered over broader areas.
In some cases, predator numbers can recover rapidly following baiting. Under favourable conditions, feral cat and fox populations can double in a year, while dingo populations can grow 50% annually. But, under average conditions, such high rates of population increase are likely uncommon.
Predators from outside the control area can rapidly repopulate areas after a baiting program. For example, multiple studies have found no change in fox numbers even when baiting was conducted at monthly intervals. Similar results have been found after intensive fox shooting.
But there are also examples where prolonged, broad-scale baiting has worked well. To protect the threatened yellow footed rock wallaby, researchers baited around wallaby populations in New South Wales and South Australia and largely eliminated foxes from large areas. Wallaby numbers then increased.
2. Feral cats take baits too
Feral cats are opportunistic ambush predators and hunt a wide range of prey. They’re visually driven and prefer fresh meat. For these reasons, it’s long been thought they are less likely to eat poisoned bait than foxes and dingoes.
But our analysis doesn’t support this – feral cats appeared to be just as susceptible to baits as foxes and dingoes. That’s good news for wildlife.
Significant and ongoing work has been put into designing better baits for feral cats to increase consumption rates. The most widely known of these baits is Eradicat, a sausage-style bait.
While this bait is aimed at feral cats, our analysis didn’t provide strong evidence showing Eradicat actually killed more feral cats than other poison bait recipes. This suggests any bait is more effective than no bait when it comes to cat control.
Eradicat baits have to be sweated to bring out the oils and make them more appealing.
Luke Bayley, CC BY
3. Blanket coverage works better
In land manager circles, there’s a long-running debate over how best to bait. Some advocate putting out more baits over the same area, while others suggest more frequent baiting is better.
So which is it? Our analysis shows more baits in an area is likely to equate to better control of predators, while distributing baits more frequently may not have the same effect.
Why is this? Like people, animals are individuals, with their own behavioural tendencies. Wary animals may never take baits. Some foxes are known to store baits to eat later, by which time the baits may be less toxic, sickening rather than killing the animal.
This is believed to lead to bait aversion, where foxes avoid baits in the future due to previous bad experiences – just as we might avoid foods which made us sick.
A single, more intensive application of bait is likely to work better because susceptible predators eat the bait and die, and there is limited opportunity for bait aversion to develop. In contrast, more frequent baiting in a short period of time are of limited benefit because animals learn to avoid them.
Dingoes have been routinely baited for decades.
Ian Mayo, CC BY
Fresh baits have long been believed to be eaten more readily than dry baits.
But our analysis shows this may not always be true. Overall, the type of bait had little impact on whether or not it led to reduced predator survival.
Optimising baiting
More efficient control of predators will mean fewer baits are needed to achieve the same result. That, in turn, means less risk of harming other native animals, as well as reducing how much work and money it costs to control feral cats, foxes and dingoes.
Our research shows baiting does indeed cut the number of predators prowling an area. But it also shows many factors we thought were important in making a baiting program effective may only have a limited effect.
The goal of poison baiting is to reduce the damage predators do to livestock and wildlife. Baiting is an important and effective tool in reducing predator pressure on threatened species. But its efficacy – and the risk other animals could take the bait – means we have a responsibility to continually optimise its use and ensure its application is targeted.
Authors: Pat Taggart, Adjunct Fellow in Ecology, University of Adelaide
