Tasmania Bandicoots Still Haven't Learned to Fear Dogs

The marsupials don't see the canine predators as a threat, even after living with them for two centuries, new research shows.

Bandicoots on the island state of Tasmania fail to recognize dogs as a threat, despite co-existing with the domesticated predator for 200 years, a new study shows.

The finding, published today [September 7] in the journal PLOS One, builds on previous work that reveals while bandicoots in Sydney have learned to avoid domestic dogs, they do not recognize cats as a predator.

Taken together, the studies suggest the arrival of dingoes in continental Australia 4,000 years ago may have helped mainland bandicoots become dog smart.

They also suggest that predator naivety is not forever, said co-author Peter Banks, a professor in conservation ecology at the University of Sydney.

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In a previous study Professor Banks and his team surveyed residents in northern Sydney and asked them whether they saw bandicoots in their backyard, whether they had cats or dogs and details about the vegetation of their garden and surrounding area.

"We found the people saw bandicoots less often in their yard if they had a dog, but not if they had a cat," he said.

This suggested bandicoots recognized dogs as predators and avoided areas where dogs were present, Professor Banks said.

The lack of response to the presence of cats suggested to the researchers that Sydney bandicoots had been predisposed to avoid domestic dogs through 4,000 years of exposure to dingoes.

To test this theory, the team replicated the study in Tasmania - while dogs have been present there for 200 years, dingoes have never made it across the Bass Strait.

"We predicted the [Tasmanian] bandicoots would show the same response to dogs as [Sydney] bandicoots do to cats on the mainland ... because they haven't learned to avoid dogs," Professor Banks said.

The latest study harnessed citizen science, with the researchers surveying 548 people in Hobart about bandicoot sightings and scats in their backyards.

Of those involved, 37 per cent owned at least one dog, 20 per cent owned at least one cat and more than 25 per cent reported that their pets had killed bandicoots.

But critically, the survey showed that Tasmanian bandicoot sightings and scats were equally likely in backyards with or without domestic dogs or cats.

Professor Banks said the finding overturned the notion that "alien species are forever alien".

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Worldwide, introduced predators have caused declines and extinctions of native wildlife, in part because native species do not see novel predators as threats and fail to flee or defend themselves.

"[Adapting to introduced predators] can take a long time - and 200 years since cats and probably foxes arrived perhaps isn't long enough and we are still in the phase where animals are naive - but 4,000 years is long enough."

Professor Banks said other studies had attempted to speed up the process of adapting native species to new predators with varied success.

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PhD candidate Ms Sarah Maclagan studies southern brown bandicoot populations outside Melbourne and said while the study was consistent with the idea that Tasmanian bandicoots are naive to dogs and cats, more evidence from other cities both with and without a history of dingoes is needed before drawing any conclusions.

"My experience of bandicoots in peri-urban Melbourne is that they are highly adaptable, readily taking advantage of new habitats and food sources, so I would also expect them to learn to recognize new predators pretty quickly."

She said other differences between the Sydney and Hobart populations could explain differences in behavior.

"It could be that bandicoots are aware of cats and dogs as potential predators, but that they trade off the risks against the potential gains to be made from entering backyards [such as pet food]," Ms Maclagan said, adding that the bandicoots in her study often used yards that had dogs.

"I had even wondered whether bandicoots might be selecting dog-inhabited yards to avoid foxes [since dogs keep foxes away]."

Ms Maclagan said the bandicoots might also reduce their risks in more subtle ways such as entering the yard only at times of day when dogs or cats are less active, or by staying close to dense vegetation cover.

Article first appeared on ABC Science Online.

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