There are few things more relaxing than walking through nature, seeing the beauty and enjoying the sounds of animals.

If you happened to be doing this in Germany in 2005, however, you might have heard something very unexpected.

Exploding toads.

That’s right, beginning in April, media reports started rolling in saying that thousands of toads had exploded in the area around Hamburg’s Altona district. One BBC News report said that the toads would bloat up to 3-4 times their normal size and then explode, sending their insides as much as a meter in the air.

One pond was reportedly home to thousands of these toads, and local authorities instructed parents to keep their children out of it until things could be figured out.

These exploding toads weren’t isolated to one pond, or even one country. A pond near Lassaby, Denmark also reported experiencing these exploding toads.

Naturally, scientists began running tests on the water, and even on the toads themselves. Some suspected that an unknown virus had infected them. Others thought that it could be from a fungus. Nobody knew for sure.

Frank Mutschmann is a leading herpetologist in Germany. He collected both living and dead toads from the area and began studying them. What he found was that all the toads had an unusual circular incision on their backs. In a report by the Independent, he said:

“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. It was clearly the work of crows, which are clever enough to know the toad’s skin is toxic and realize the liver is the only part worth eating.”

That’s right, the highly intelligent crow figured out that it could eat the nutritious toad liver without getting sick from the poison. It made for an easy meal for the crows, but why did it result in exploding toads? Mutschmann went on to explain:

“Only once the liver is gone does the toad realize 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.”

Oddly, reports of exploding toads stopped coming in. It isn’t clear why this would happen. It could be that the crows moved on to other food sources, or maybe the toads figured out how to avoid the crows more effectively.

Whatever the case, this was one of the most unusual natural events to occur. If you hear an odd popping sound while out in nature, however, it might be a good idea to watch out for crows.

If you thought that was interesting, you might like to read about the mysterious “pyramids” discovered in Antarctica. What are they?