Are cats the cause of dog disappearance?

The mystery that sparked international debate has been revisited in a new study.

Back in 1991, the wild dogs of the Serengeti National Park in Tanzania mysteriously disappeared. Now a team of biologists think they know what happened.

A controversial and influential 1990s theory, which still reverberates, was that the dogs were killed inadvertently by efforts to protect them. Many had been tranquilised and radio-collared, leading some to suspect this stressful procedure weakened their immune systems, leaving them susceptible to rabies or canine distemper.

Craig Jackson of the Norwegian University of Science and Technology, who led the latest study, says that though there was scant evidence from elsewhere in Africa that radio-collars were harming wild dog packs, there was room for doubt when comparing different

populations in different countries in different ecosystems with different disease pools. But his study of wild dogs in nearby habitat, surrounding the Serengeti plains, is about as comparable as one can get. Of 121 animals tranquilised, 105 survived the following 12 months, the period in which they should be most vulnerable.

Marion East of Berlin’s Leibniz Institute for Zoo and Wildlife Research, one of the team who raised the issue of radio-collars in the 1990s, is not convinced. Among her concerns is that after handling, dogs in the recent study were kept for unspecified periods in holding enclosures, which would boost the cited 12-month survival rates by preventing exposure to disease and predators. “This is not the standard of science required for an endangered species,” she says.

But if Jackson’s right and it wasn’t the collaring, what was it? He suspects it’s lions. “Wild dogs avoid lions at all costs in space and time,” he says. “Lions are the big apex carnivore. They are able to monopolise the areas with a lot of prey.”

And that means the Tanzanian plains. This would also explain why the wild dogs haven’t recolonised, despite living so close and despite efforts to reintroduce them.

So, why were dogs there in the first place? “Since wild dog studies on the plains started in the 1960s, the lion density on the plains has tripled,” says Jackson. Stuart Blackman

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Ecology & Evolution: bit.ly/Serengetidogs

Unlike these healthy wild dogs in Botswana, those of Serengeti NP died out in the 1990s, and a new study suggests the reason why.