Whales are some of the largest creatures ever to appear on Earth, so when they wash ashore after death it's no small task to remove the carcass. Because of the incredible size, the whale must be cut into smaller and more manageable pieces. The act of cutting it up poses yet another obstacle: dead whales can explode when punctured.
At the time of the whale’s death, it begins to decay. The internal organs and all of the food it consumed before dying begin to rot. As bacteria swoop in to decompose the animal, they generate heat and gasses that build tremendous pressure inside of the whale. When biologists cut into the whale to remove or study it, the gas comes exploding out and can bring blood and internal organs with it.
There are actually three gasses behind this phenomenon: methane, ammonia, and hydrogen sulfide. As you might imagine, this combination smells really, really bad. Methane is a by-product of digestion, ammonia is what gives cat urine its distinct pungent odor, and hydrogen sulfide is the gas that smells like rotting eggs. So, if you can imagine a whale-sized fart/cat pee/egg bomb with blood and entrails flying at your face, that’s pretty much the full experience of an exploding whale.
Check out this amazing, and obviously graphic, footage of a whale exploding that originally appeared on Faroese Broadcasting Corporation. Good thing he was wearing a rain coat: