Protecting our native mammals from their predator, the fox

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I was doing an honors project in my fourth year, catching small mammals and testing ideas about what factors limit their numbers during the winter and whether they were food limited. But I had a fox that disturbed all my traps. It got me interested in foxes.

Then I had the chance to do a PhD in the Australian Alps looking at their impact, working with CSIRO on plans to introduce an agent to sterilize them, but for all sorts of reasons the plan didn’t worked. My research turned to examining the impacts of foxes on native small mammals, rabbits and kangaroos. I also examined the behavioral responses of these native animals. Were they naive towards foxes? Did they recognize them? Since then, I’ve kept an interest in trying to figure out what impact they have, what the nature of the impact is, how it works – and then, most importantly, how we can potentially stop it.

Foxes alone kill more than 300 million native mammals a year.

The introduction of foxes and cats to Australia has been devastating to our native wildlife. A recent study found that cats and foxes wipe out 697 million reptiles, 510 million birds and 1.4 billion small animals each year in Australia. Just huge numbers. Foxes alone kill more than 300 million native mammals a year. There are around 20 mammals that are likely extinct or drastically reduced due to foxes and cats in Australia.

Fox hiding among the shrubs in West Melbourne. Credit: Chee Leong Wong/EyeEm/Getty

And all that killing is on top of the mortality from natural predation, creatures like goannas and other native predators here, so all that predation is additional – we did a study showing that introduced predators have twice as much impact than native predators, and the reason for this is probably that Australian mammals do not show the right kinds of responses to these new predators. Either they don’t recognize them as dangerous, or they react in a way that is simply not suited to this type of predator, or they simply get left behind.

Foxes are truly a global success story – they are the most common carnivores besides domestic dogs.

Foxes are truly a global success story – they are the most common carnivores besides domestic dogs. They are beautiful animals in their own right. You have to admire their adaptability and flexibility. Here in Sydney’s mid-west, there are foxes in the park, just opposite my house. And then there are foxes in the Simpson Desert. They are incredibly adaptable and flexible, and they can succeed anywhere. It’s just that there’s such a disconnect between what they do to hunt and what our native animals can do to avoid predation.

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Red fox feeding a red kangaroo carcass. Credit: Ken Griffiths/Getty

It would be an uphill battle trying to eradicate 100% foxes in Australia. Some people would like to use genetic modification to try to control these pests, but that’s still a long way off and comes with ethical hurdles. Unfortunately, the only type of blunt tool we have at the moment is poisoning or other lethal control, but it doesn’t get all problem animals – individual animals can cause particular problems with their own type of personality. Some of them are just surplus killers.

Alternative tactics are needed. We must try to outsmart them.

One of the methods we are developing, with Dr. Catherine Price from USYD, is to take the information they use to hunt, their sense of smell, and make that information useless to them. Foxes find many native species by smell; they track them down by finding where they are hiding by their scents.

We have shown that foxes study the smells of species they have never encountered before as potential food.

We have shown that foxes study the smells of species they have never encountered before as potential food. We exposed foxes in western Victoria to the smells of bandicoot nests where bandicoots never occurred, and the foxes visited these smell points and sniffed for a meal on the first day.

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The Southern Brown Bandicoot is listed as an endangered species in New South Wales. Credit: ozflash/Getty

We’re trying to neutralize that effect by basically teaching them that chasing that particular scent doesn’t lead to a reward. By spreading this scent widely, foxes cannot pinpoint exactly where their prey is and they quickly learn to ignore unnecessary information.

We have had success with this in a number of circumstances. It all started with working on mice in enclosures and watching how they use smells to find food. We then showed that we could use the technique to prevent rats from finding bird nests and attacking eggs. We then took it to New Zealand on a large scale in conjunction with Landcare Research, trying to protect some endangered bird species that breed on the braided rivers coming from Mount Cook and are threatened by ferrets , hedgehogs and cats. And we have shown that the technique can double the breeding success of birds in a few years. If this success continued, it would completely reverse their population decline – and that without killing anything.

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Landcare Research in New Zealand has an ambitious goal of ridding the country of the most damaging small mammalian predators by 2050 in order to protect native species, such as the Kākā, the New Zealand parrot. Credit: indiginz/Getty

We have generated interest in this idea and are currently in discussions with a number of people in Australia and overseas to try and stop problematic predators, not just introduced foxes. Sometimes these problematic predators are native, sometimes they are introduced but culturally important, so killing is not an option.

The use of this type of non-lethal technique is what has been called “nudging”. We just nudge the predators in a different direction without hurting them, but they can go on and on eating things like introduced rabbits and rats, which is potentially a good thing. It’s just the critical things we don’t want them to kill – we make them hard to find.

Every predator wants this easy meal. Because predators are hungry and motivated to eat, they can’t hunt labor-intensive things. So we use this disinformation technique to exploit their motivation.

Sometimes these problematic predators are native, sometimes they are introduced but culturally important, so killing is not an option.

We have many proofs of concept. Now we are trying to determine the exact mechanism of how we can apply it profitably. We don’t yet know how often we have to expose them to it, or how difficult the hunt has to be. But their hunger means they can’t keep looking for meals that don’t exist, and that’s something they can’t develop adaptations to overcome.

Foxes, like many mammals, navigate their landscape with their noses. We need to use this disinformation strategically. But it does seem like smell is a valuable new tool in our toolbox to try and stop the damage these predators are doing.


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