ROXBY DOWNS, AUSTRALIA—Katherine Moseby delves into a freezer at this arid mining outpost and pulls out the carcass of a pointy-faced animal the size of a rabbit. It’s a dead greater bilby, or at least what is left of one. She runs a cotton swab along a rip left in the bilby’s soft fur by the teeth of its killer. Later, analysis of DNA from the wound confirms Moseby’s suspicions: This bilby, a threatened species, was slain by a domestic cat.
Over the past 25 years, the ecologist, who works for the University of New South Wales (UNSW) in Sydney, Australia, has examined hundreds of native Australian animals killed by introduced predators, including domestic cats that have gone feral. The native fauna are often easy prey because they haven’t evolved to recognize and dodge the invaders, and medium-size mammals like the bilby have fared worst. Nearly three dozen Australian mammals have gone extinct since Europeans arrived, and although fences and predator eradication efforts have slowed the march toward extinction, Moseby wants to do better, perhaps by accelerating natural selection.
For nearly 5 years, a team she helps lead with Michael Letnic at UNSW and Daniel Blumstein at the University of California, Los Angeles, has been placing bilbies and another threatened species into large fenced plots together with their feline enemies in hopes that, faced with extreme selective pressure, some individuals will learn or adapt to avoid attacks. Results published today suggest the “vaccination” approach has promise: Bilbies exposed to cats in a controlled setting were more likely to survive later, when they were released among feral cats, than those that hadn’t been exposed, they report in the Journal of Applied Ecology.
The results are “a tantalizing piece of encouragement” for conservation efforts, says biologist Sarah Legge of Australian National University in Canberra. But some experts wonder whether the strategy can become widespread.
As a child, Moseby adored her pet kitties and excused their habit of killing wildlife. But after becoming a conservation biologist and facing the massive toll cats take on Australian fauna, she orchestrated the deaths of thousands of feral cats. But cats are difficult to eradicate and, after watching them defeat numerous efforts to reintroduce rare species, Moseby realized, “We had to think of a different way of doing things.”
A key testing ground for those innovations is the Arid Recovery Reserve, a 123-square-kilometer research site that Moseby and ecologist John Read (who is also her husband) helped create in 1997 in the desert of South Australia. Here, in a landscape of olive-green acacia bushes and rust-red sand dunes, the researchers cleared out nonnative animals such as foxes, rabbits, and cats, and fenced the reserve to keep them from returning. Then, they began to place native rodents and marsupials inside and run experiments. In one early test, “We actually chased wild bilbies and rubbed them with a dead cat” to see whether that would help them avoid the predators in the wild, Moseby recalls. (It didn’t.)
More recent efforts have involved intentionally adding cats to a 26-square-kilometer pen, then seeing whether the native animals living there develop different behaviors or anatomy. Inevitably, some of the native animals die. “To actually catch a cat and add it to an area where there were threatened species was a very strange moment,” Moseby says. “A lot of people were very upset about it.”
Yet in as little as 18 months, the researchers noticed behavioral changes in the animals living with cats, which included bilbies and burrowing bettongs, a marsupial also known as a rat kangaroo. Both species became warier; cat-exposed bilbies, for example, grew slower to emerge from artificial burrows and tended to avoid unprotected areas after emerging. And, over four generations, bettongs developed larger hind feet, which Moseby speculates might help them evade or fend off cats. She suspects such changes are heritable, but her team hopes to find out. In one possible test, they may swap young animals between pouches of cat-savvy and cat-naïve parents to see whether the young grow up behaving like their biological parents or their new, adoptive ones.
In the experiment reported this week, UNSW doctoral student Alexandra Ross released 42 radio-tagged bilbies—half of them cat-savvy and half cat-naïve—into a 37-square-kilometer pen with 10 feral cats. Then, the researchers monitored bilby survival for 40 days. The fate of the tagged animals revealed the advantage of prior exposure to cats: Cats killed 71% of the naïve bilbies but just a third of the savvy animals.
Despite the short duration of the experiment and the small sample size, the results are promising enough that Bush Heritage Australia, a conservation group based in Melbourne, is now working with the researchers on a bigger test. Next year, they plan to release cat-savvy and cat-naïve bettongs into the Bon Bon Station Reserve, a 2100-square-kilometer, unfenced reserve 650 kilometers northwest of Adelaide, Australia, and then track them for a year using radio collars and camera traps.
Whether the approach could help other endangered animals cope with predators is unclear. For instance, Andre Raine, a seabird researcher at the Kauaʻi Endangered Seabird Recovery Project in Hanapepe, Hawaii, doubts the petrels and shearwaters he is trying to save can adapt to avoid the cats and rats that plague their nests.
Moseby would be content to save the unique marsupials she has defended for so long. “If I could see bettongs in the wild, in my lifetime, coexisting with cats,” she says, “I wouldn’t care if it takes 20 years.”
Reporting for this story was supported by the Solutions Journalism Network.
Source: Science Mag