Toads are exploding in Hamburg, Germany, and scientists can't figure out why.

No, it's not a joke.  Toads really have been exploding in Hamburg.

It's like "a science fiction film," said  Werner Smolnik, a member of a Hamburg nature protection society, in an AFP story. "You see the animals crawling on the ground, swelling, and then exploding."

Over the last few weeks, some thousand toads have come to an explosive end in one particular pond in Hamburg, now known as "the pond of death."  And while it seems like tabloid-fodder (the Daily Mirror and Daily Mail did indeed cover it), the story of the bursting batrachians has caught the attention of serious newspapers like the Sunday Telegraph too.

"I could hardly believe what I saw," Smolnik told the Telegraph.  "Dozens of toads were crawling out of the water.  They were puffed up to almost three times their normal size and making strange screeching noises.  Then they just started popping.  Some just went 'phut!'... but others literally exploded."

The circumstances of the toads' excessive inflation were just as strange as the phenomenon itself.  Toad casualties only began appearing with the start of their mating season, and most of the toads seemed to burst between 2:00 a.m. and 3:00 a.m.  Also, though the pond is host to frogs as well as toads, only the toads met grisly ends; the frogs remain hale and whole.

The city of Hamburg, fearing a chemical spill into the pond, quickly launched an investigation, but the emergency team turned up no toxins, nor any thing else that would explain the toad phenomena.  Viruses, bacteria, and fungal infection theories were put forward, inspired by the presence of South American horses at a nearby race track.  Investigators found no evidence of any disease or infection, however.

There was one theory that was supported, though: bird attacks.  The veterinarians who examined the toads' remains found that all bore incision marks. 

"We think that birds may have attacked the toads and eaten much of their entrails,'' Anke Himmelreich told the Telegraph. "It is possible that the toads survived the attacks and then filled up with water through the incision made in their bodies. After that they simply burst open.''

German amphibian expert Frank Mutschmann, quoted in the Independent, agrees.  He found that all the toads' livers were missing - evidence that crows were to blame.

Although the bird attack theory may seem dubious (as it does to Smolnik - "If birds were responsible we would have seen them attacking the toads en masse, but we saw nothing of the kind," he told the Telegraph), it would take only a few crows to do the damage, according to Mutschmann.  Three to five crows could kill around 100 toads by themselves, he told AFP.

The fact that it was mating season was likely a contributing factor in the toads' deaths.  With their attentions elsewhere, the toads were easy pickings for the crows.  "They would have noticed something as the crow pecked at them, but it wouldn't have been particularly painful," Mutschmann told the Independent.

In fact, the Independent reports that exploding toads are not a new phenomenon: they've apparently been reported as early as 1968, in Germany, Denmark, Belgium, and even America.  And though it may seem a particularly unpleasant way for the toads to go, it's a perfectly normal occurrence, really.

"I've had several angry emails," Mutschmann told the Independent. "But there's no reason to worry. It's just a part of nature."