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Extinction: Do introduced predators such as foxes and cats deserve their bad name?


According to a recent study reported in Scientific American, Australians may overestimate the risk that cats and foxes (introduced predators) do to endangered native wildlife. They have reason for concern:

The continent has suffered more than a quarter of all recent mammal extinctions, and many other native species survive only as small populations on one or more of the country’s thousands of islands. While habitat destruction has caused some extinctions, cats, foxes, and rats introduced around 1800 by British sailors have also played a major role, decimating native animals like bilbies and bandicoots—both small, ratlike marsupials found only in Australia.

Is the solution to “hate” cats and foxes, which one conservation biologist identified as a general view? Not so fast. One study, using a “ridiculously” large database:

… yielded some surprising results: Native mammals were most likely to die off on islands that had rats, but not cats, foxes, or dingoes. Extinction rates on such islands ranged from 15% to 30%, but when cats, foxes, or dingoes were present, the rates plummeted to just over 10%—not much higher than on islands without any introduced predators, the scientists reported at the meeting and online this month in the journal Global Ecology and Biogeography.

The scientists also found that native mammals fared only slightly worse on islands with cats than on islands without them. Moreover, the presence of foxes and dingoes on islands seemed to give native species a slight overall boost. “I was really surprised,” Hanna says. “I thought I’d made a big mistake.” Hanna and Cardillo also found that rats’ impact was most pronounced on small mammals—those weighing less than 2.7 kilograms—although the scientists are unsure how much of this influence was due to direct predation as opposed to competition for food and other resources or disease spread. Rats also had the greatest effect on islands within 2.1 kilometers of mainland Australia.

This makes sense. Rats have survived the most intense global persecution by humans of almost any species; most people would be glad if they went extinct— and yet they bounce right back in force.

Foxes are hunted, to be sure, but the success of the business requires a fox. And cats have been bred and pampered for centuries. Thus, these species’ predations might be more noticed than those of rats, not necessarily more severe. A study of this type, which accurately identifies the sources and rate of depletion, should help conservationists identify the type of action needed and where.

It certainly beats useless anti-cat propaganda. Note: The picture in the linked scare story is curious, as it shows a cat carrying off what looks like a park pigeon, not exactly an endangered species or one basic to a natural ecology.

The marsupial wolf went extinct not long age as it was seen as a wolf. it was a wolf but with a pouch. Same as all of them. Robert Byers

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