What happens to dead whales?

How do whales die? Do dead whales float or sink? How do people dispose of stranded whales? If you’ve ever wondered about whales’ life after death? Find out everything you need to know in this post!

Credit: https://www.flickr.com/photos/38623372@N06/9511546661

Lifespan and causes of death

Whales generally live long lives, sometimes even surpassing humans’ lifespans. Bowhead whales are by far the oldest whale species, living up to 200 years! Most other baleen whales’ lifespans range from 50 to 100 years. The smaller dolphins and porpoises generally live a few decades.

Many whales die of old age or natural causes such as predation or disease. Unfortunately, anthropogenic (human) threats are also significant causes of whale deaths. Thankfully, our long, bloody history of hunting whales has ended in most parts of the world. However, other human-related risks are becoming more abundant—plastic and chemical pollution, entanglements, ship collisions, and overfishing are responsible for many whales’ deaths. Bycatch alone kills at least 300,000 cetaceans each year!

What happens to dead whales?

Burial at sea

When a whale dies at sea, its gas-filled and blubbery body usually stays afloat for a while. The floating time varies among individuals and species. Still, species with more blubber generally float longer. In fact, blubber-rich species such as right whales and bowheads were easy whaling targets because their huge amount of blubber made them float longer.

Seabirds and sharks may peck and bite the floating carcass, but the real feeding frenzy begins when the body sinks to the ocean floor. A whale carcass is like a gift sent from above to the deep sea; the ocean floor is usually barren and nutrient-poor. Enter a multi-ton whale, and the dinner party can begin.

The whale carcass attracts sleeper sharks, crabs, and hagfish, who eat the blubber and meat in the first year or two. When all the good stuff is gone, the phase “enrichment opportunists” commences: worms, mollusks, and crustaceans feed on organic matter in the bones and any leftover fat. After about two years, the whale is stripped bare of any organic material, and all that is left is a skeleton. Yet, it is not the end, as deep-sea organisms literally go to the bone when it comes to eating a whale carcass.

The leading players in this third phase are sulfur-reducing bacteria and the not-so-glamorously named zombie worms (it worsens; one species of zombie worm goes by “bone-eating snot flower worm”). They extract fats and oils from the skeleton and break down the whale’s bones. From start to finish, the whale’s decomposition can feed abyssal organisms for up to a century.

A bad case of gas

The decomposition process of a beached whale is far less charming. Gas builds up in the stomach, whereafter two scenarios can follow. In the first scenario, the whale slowly deflates as the gas flows out through the whale’s disintegrating skin. It’s a smelly business but nowhere near as dramatic as the second scenario. Sometimes, the gas cannot escape through the whale’s thick blubber and tough skin. The gas piles up, and … BOOM! The whale explodes. Natural explosions of dead whales are relatively rare, but the explosion risk increases incrementally with human interference. Thanks to countless curious individuals who tried poking stranded whales, viral videos of exploding whales are all over the internet. So if you ever see a beached whale, whatever you do, do not use it as a trampoline (I am serious; this has happened).

How do we dispose of stranded whales?

No one wants to leave a stranded whale on the beach for too long; a dead whale is a sad sight, a health hazard, not to mention a smelly mass of rotting flesh and explosion risk. When a whale strands, a team of scientists ideally performs a necropsy (an autopsy for whales) to determine the cause of death or collect samples that reveal more about the species’ biology. After that, they need to dispose of the whale, but it is easier said than done. It is no news that whales are huge and difficult to handle – moving them requires expensive and heavy machinery. One way to dispose of a whale is to tow its body back to sea, where it can fulfill the useful post-mortem function of enriching the deep seafloor. Another option is to dig a 10-feet-deep hole in the sand and bury the stranded whale right on the beach. Finally, they could cut the whale into pieces to throw out at sea, onto a landfill, or incinerate.

Conclusion

Dead whales are more than just smelly gas-giants. The ones that die at sea play essential roles in feeding deep-sea creatures, while beached whales offer researchers the opportunity to get an up-close look to advance scientific knowledge or go out with a bang (literally) if they explode. Whales’ relevance does not die with them; they remain vital for the ecosystem and stay interesting long after they’ve breathed their last breath.


Thank you for reading! If you liked this post, you might want to read about why whales beach themselves:

Massive graveyard in Tasmania: Why do whales beach themselves?

Eline van Aalderink is a recent MSc Marine Biology graduate from the University of Groningen (the Netherlands), where she specialised in marine mammal ecology and conservation biology. She is currently working as a marine mammal research assistant/supervisor at Archipelagos Institute of Marine Conservation in Greece.

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