Why do beached whales sometimes explode?

Chris Smith askled Anglia Ruskin's Danielle Green...

Dani - The reason that they explode and, actually, they don’t explode as often as people think that they do. There have been some horrendously documented cases of it on youtube because it does happen, unfortunately, sometimes. Basically the microbes in their bodies and their guts are still degrading them and this is releasing gas. They’ve got very thick skin so that this gas isn’t easily released from the body, so they will bloat up and sometimes they can explode. Sometimes they explode because people are jumping on them, so never a wise thing to do - not a good idea.

What are they doing on the beach in the first place? Whale strandings are quite a common phenomenon and there’s a lot of evidence to suggest different theories. There are natural things that can lead to this, so disturbances in the weather. Sometimes, smaller whales like pilot whales will be herded in by large predatory whales like killer whales and they’ll end up being stranded on the beach.

Unfortunately, there’s quite a bit of recent evidence to suggest that it’s anthropogenic noise, so that’s noise made by people. The ocean’s an extremely noisy place anyway, but there’s a lot of evidence that sonar from military operations is affecting the navigation systems because the whales use echolocation. And there's correlations between them coming up from the deep too quickly and developing decompression sickness as well and they can get hemorrhaging from really loud noises. Some of the noises used by military and boats are extremely loud (hundreds of decibels) and they can actually get hemorrhaging in their ears, and they use their ears to echolocate so this can put them off kilter and they’ll become stranded. So there’s quite a lot of evidence that human noise could be an issue as well, but there are natural reasons too.

Chris - Weren't you saying something, Duncan, about people actually dynamiting these whales? Not before they’re dead, obviously, but when they’re on the beach to get rid of them and clear up the mess.

Duncan - That is what I naively believed. Before you just gave that answer I thought it’s just an efficient way of disposing of a very large whale. Just blow it up and then seabirds and so on will eat it.

Chris - Because that would make quite a stink.

Carolin - I wouldn’t be surprised.

Duncan - That’s just what I thought was true. I’ve no evidence to base that on whatsoever, and I’m so glad that you’ve put me straight.

Carolin - The humble microbe strikes again.

Chris - I think, taking a historical perspective for a minute, Henry VIII wasn’t quite whale size but he was getting there towards the end of his life, and I think it was a very hot day when he died. The history books, and I think people will bear me out on this, he did explode for a very similar reason. As you say, he fermented internally and there was a pocket of gas that built up and Henry VIII was no more.