What Is Killing South African Crocs?

Mass deaths of South Africa's Nile crocodiles puzzle biologists.

Carcasses of adult crocodiles do not usually signal the return of winter in South Africa, but mass death seems to be becoming the harbinger of the season. Rangers at the Kruger National Park have found Nile crocodiles floating in the Oli­fants River or bloated and decaying along its banks. Investigators are rushing to figure out the cause and worry that the deaths might be signaling the presence of toxins or pathogens that could threaten not only the croc population but also the livelihoods of the people living near the river.

...The first sign of croc trouble in the river came in the winter of 2008, when rangers collected 170 dead individuals, sometimes at a rate of 20 bodies a week. A survey at the end of this May showed nearly 400 crocs living in the park’s gorge, down from at least 1,000 in 2008. So far, as of Au­­gust 7, rangers and scientists have found 23 carcasses.

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