Moving Animals to Safe Havens Can Unexpectedly Doom Them

Despite everything that had been done to save them, the quolls were still dying. And this time, it wasn’t for the expected reason.

Quolls are small Australian mammals that superficially resemble ferrets, but are more closely related to kangaroos and koalas. Being hunters, they tackle all kinds of small prey. But if they attack cane toads—large invasive amphibians that were introduced to Australia in the 1930s—they get a mouthful of poison, and inevitably die from violent seizures and heart attacks. As the toads spread through the continent, the northern quoll—the smallest of the six species—started disappearing. In some places, 90 percent of them vanished. In other sites, they went completely extinct.

To save the species, conservationists collected 64 northern quolls in 2003 and relocated them to two toad-free Australian islands: Pobassoo and Astell. In these sanctuaries, the animals flourished. Within a decade, they had become so abundant that scientists began to think about reintroducing them to their former homes. Ben Phillips, from the University of Melbourne, started training the island-born quolls to avoid cane toads by feeding them with toad sausages laced with noxious chemicals. Sure enough, when released on the mainland, the trained quolls avoided the toads, while untrained individuals quickly died. The plan was coming together.

“But we encountered a new problem,” says Chris Jolly, who’s also from the University of Melbourne and works with Phillips on the reintroduction project. “We were losing the quolls to predators. I would be radio-tracking the quolls and sometimes, I’d end up radio-tracking a dingo with a GPS collar in its belly.”

A dingo (Ryan Francis)

Dingoes are feral dogs that have been in Australia for around 3,500 years, and quolls have had plenty of time to adapt to their presence. But island-born quolls, which had never encountered dingoes, have no instinctive fear of them—or of other lethal threats, like cats. In an experiment, Jolly showed that mainland quolls mostly stayed away from food sources that were laced with hair from dingoes or cats, while island-born quolls were largely unperturbed.

More surprisingly, the offspring of the mainland and island quolls showed roughly the same pattern as their parents, even though all of them had been raised in captivity and none of them had experience of predators. Those born to mainland parents were wary of eau de dingo; those born to island parents were not. This suggests that the quolls’ aversion to predators is at least …read more

Source:: The Atlantic – Science

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