After weeks of flummoxing scientists, Germany's great exploding toads mystery has been solved. They were gruesomely murdered by crows with a taste for foie gras.

After weeks of flummoxing scientists, Germany's great exploding toads mystery has been solved. They were gruesomely murdered by crows with a taste for foie gras.

Health officials in Hamburg started to panic after some 1,000 toads puffed up and exploded last month, their entrails splattering an area of up to a square metre. The tabloid press went into overdrive, dubbing the carnage site in Hamburg's Altona district the "Pond of Death" and warning children and dogs to stay away. Theories ran wild that toads were committing suicide or were croaking because of a virus spread by South American race horses. But now one of Germany's top experts on amphibians says he's cracked the case. Frank Mutschmann, who examined both dead and living Hamburg specimens at his Berlin research centre, found all had identical circular incisions on their backs, small enough to be the work of a bird's beak. Then he found something strange: their livers were missing. "There were no bite or scratch marks, so we knew the toads weren't being attacked by a raccoon or rat, which would have also eaten the entire toad," he said. "It was clearly the work of crows, which are clever enough to know the toad's skin is toxic and realise the liver is the only part worth eating.

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"Only once the liver is gone does the toad realise it's been attacked. It puffs itself up as a natural defence mechanism. But since it doesn't have a diaphragm or ribs, without the liver there is nothing to hold the rest of its organs in. The lungs stretch out of all proportion and rip; the rest of the organs simply expel themselves."

The toads' grisly deaths are, in fact, a well-documented phenomenon. First recorded in Germany in 1968, exploding toads have been reported in the country, as well as in Belgium, Denmark and America. Hamburg's toads started to explode during their week-long mating season. Dr Mutschmann believes the crows went in for the kill when the toads were too busy enjoying the heights of sexual excitement. "They would have noticed something as the crow pecked at them, but it wouldn't have been particularly painful," he said.

The riddle solved, the question now is whether to exact revenge on the crows. Toads, much-loved in Germany, are a protected species. But so are crows. "I've had several angry emails," said Dr Mutschmann. "But there's no reason to worry. It's just a part of nature."