Australia’s plan to poison killer dingoes is backfiring, of course

Dead dingoes: not good for the ecosystem.
Dead dingoes: not good for the ecosystem.
Image: Reuter/AgForce Queensland
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Like many Australian things with goofy names (think salties, bunchy top, the gympie-gympie), dingoes can be nastier than they sound. A wolf subspecies, they’re known for attacking sheep herds, tearing chunks of flesh off several of them before finally taking one to feed on, reports Modern Farmer. Ranchers complain that they find their sheep dead with only their livers eaten out. With sheep numbers plummeting—Australia’s wool industry is projected to disappear in as few as 30 years (pdf)—the government has authorized dingo “baiting programs,” which allow farmers, not just wildlife officials, to lay poisoned bait to kill them.

Australia is not the only place with predator problems. As Parisians worry about encroaching wolves, English otters are plundering prize fish. Neither is the “kill ’em” solution rare. Elsewhere in Australia, governments lay lethal traps to keep big sharks away from tourist-hub beaches. The US state of Idaho is letting hunters kill more wolves than usual to reduce the threat they pose to livestock.

That seems logical. But new research (paywall) on dingo-baiting programs shows that removing them from the ecosystem can have dramatic consequences—ones that can be hard to reverse.

Comparing Australian forests where dingoes were being poisoned to those in which they weren’t, researchers tested two theories of out-of-whack ecosystems, both of which hinge on “apex predators” at the top level of a food chain.

According to the “trophic cascade” theory, killing off apex predators allows the populations of their prey—usually herbivores—to surge. Those animals in turn gobble up an ecosystem’s plants. The “mesopredator release” hypothesis posits that the sudden absence of apex predators causes an explosion in the middle tier of the food chain, animals that the apex predator eats, but that also eat other creatures.

The scientists’ dingo research suggested not only that both of these theories were true; it also showed that trophic cascades and mesopredator releases compound each other, distorting the Australian forest ecosystem even more.

Here’s how that works: The absence of dingos in forests allows big grass-eaters like kangaroos and wallabies to thrive, as well as red foxes (an invasive species, throwing another wrench in the delicate ecosystem balance). While the swelling ranks of foxes chow down on small ground-dwelling mammals, decimating their numbers, the growing population of herbivores clears away ground cover, making it even harder for those animals to evade foxes. Which means more little dead mammals.

For those unperturbed by marsupial mices’ gloomy fate, there’s a bigger cost in all this, says Mike Letnic, a professor at University of New South Wales and lead author of the study. Namely, continuing to kill dingoes risks destroying Australia’s biodiversity. And though that might sound pretty abstract, it’s something that humans have time and again failed to anticipate—an ignorance that has caused jellyfish blooms to take over an entire sea, and a crab explosion to devour a $30-million urchin business.