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Feeding on the Dead

Meet the decomposers that keep rotting corpses and other waste from covering the planet in heaps of filth

Claudio Contreras/NPL/Minden Pictures

This carcass of a killer whale has already been visited by scavengers. Now, Osedax worms are breaking down its bones.

The Natural History Museum/Alamy Stock Photo

Osedax worms will eventually cover a whale’s entire carcass as they burrow into its bones to suck out the fat and oil inside.

Deep in the ocean, death is a delicacy. The creatures that live on the cold, lightless seafloor feed on debris and dead animals that drift down from above. Usually, the food options are tiny: plankton, shells, and poop. But when a whale carcass falls to the ocean floor, it’s like an all-you-can-eat buffet. This is called a whale fall. Scavengers like fish and sharks arrive first on the scene to scarf down the whale’s meat. When just bone and fat are left, the whale fall transforms into a fuzzy red blob. That’s because zombie worms cling to the skeleton to eat the bones!

Discovered in 2002, zombie worms, also called Osedax worms, are a unique type of decomposer. Decomposers eat the remains of other organisms and help keep carcasses from piling up like a scene from a bad horror movie. They also keep our ecosystem healthy and balanced. “Decomposition helps with recycling life,” says Jeffrey Blanchard, a microbiologist at the University of Massachusetts Amherst. “We often think of recycling like a recycling bin where we recycle bottles. Decomposers are recyclers of the natural world.”

Whale Fall
Scientists find and explore a deep sea whale fall

Feeding on the Fallen

To scavengers and decomposers, the stench of rot is as appealing as fresh-baked cookies are to you. That foul fragrance comes from bacteria springing into action. All living things are teeming with bacteria. Normally, these microscopic passengers dine on the contents of an animal’s intestines or gobble up oils and flakes of skin.

But after an animal dies, the bacteria go to work on the animal itself. This results in stinky chemical emissions that let scavengers know a meal is nearby. After the scavengers have their fill, insects, bacteria, fungi, and other tiny creatures finish the job.

NOAA

FAVORITE FOOD: WHALE FALL

In the first stage of this baleen whale’s decomposition, scavengers like sharks, crabs, eelpout fish, and octopuses come to eat the soft tissue. On its lower jawbone, a red beard of Osedax worms are busy decomposing the bone.

Breaking it Down

Bacteria also lurk in the dirt. There are hundreds of thousands of microbes in a single teaspoon of soil, waiting to decompose dead leaves, trees, and other plant matter. Some of these bacteria hang out in the stomachs of other creatures, called detritivores. Termites, for example, feast on dead trees and plants. “You think of them as eating the wood, but they’re feeding the bacteria inside their gut and poop out the decomposed material,”  says Blanchard.

All decomposers are part of the carbon cycle, which feeds every living thingincluding humans. When plants and animals die, decomposers reduce them to the elements and chemicals that they were made of. The most important of these elements is carbon. “Carbon is the building block of all life,” says Diva Amon. She’s a marine biologist and a fellow at the Natural History Museum, London. “It’s what ultimately everything comes back to.”

(c) IMAGEBROKER/Jspix/Biosphoto

FAVORITE FOOD: ELEPHANT DUNG

Dung beetles form a ball of dung and roll it away from the pile. A female will lay an egg inside and bury the dung, so the larva has a nice snack when it hatches!

A Taste for Waste

Decomposers don’t just feast on dead animals. They also help break down poop! Creatures like dung beetles help keep piles of poop from covering farmlands. They roll up dung into balls and bury their snack in the soil. It’ll either become a future meal or a place to lay eggs. Most animal poop includes undigested morsels as well as dead bacteria, salts, and other animal waste. Dung beetle larvae eat the solid waste, while adults drink the liquid part.

If it doesn’t become a meal, poop takes about a year to fully decompose. And animalsincluding humanspoop a lot, from a few ounces to hundreds of pounds per day. The same bacteria and fungi that break down dead animals and plants also go to work reclaiming the carbon and nitrogen in waste. That’s why manure, which is made up of animal waste, is such a powerful fertilizer. When it decomposes, its chemicals return to the soil, ready to feed new plants.

Minh Hoang Cong/500px/Getty Images

FAVORITE FOOD: FALLEN LOG

Bitter oyster fungi slowly break down a dead tree. This species mainly feeds on deciduous trees like beech, oak, and birch.

Delaying Decay?

All things decompose, but how long it takes varies. A small animal like a mouse can go from fresh corpse to carbon in about three weeks, while it can take a century for a whale fall to fully decompose.

Different conditions like temperature, moisture level, and pressure can speed up or slow down decay. “The deep ocean is so special because it’s extremely cold, with temperatures just above freezing,” says Amon. Because of the chill, “decomposition is much, much slower in the deep sea.”

Meanwhile, on land, “water and warmer temperatures makes decay faster,” says Blanchard. The bacteria and fungi that drive decomposition need water and oxygen to get to work. That’s why you can find amazingly well-preserved creatures encased in freezing ice or trapped in oxygen-less tar pitsthe decomposers that would normally break them down can’t survive in those harsh conditions.

Regardless of how long it takes them, decomposers help ensure that our world isn’t overrun by death and decay. “If nothing fed on dead animals,” says Amon, “there’d be carcasses everywhere.”

Unit Rate
Watch an instructional video about unit rate.

Use rates to compare how different organisms decay. Round all answers to the nearest whole numberRecord your work and answers on our answer sheet.

After a whale’s carcass lands on the seafloor, scavengers chow down on its soft tissue at a rate of 50 kilograms per day. This process takes 548 days. What was the weight of the whale’s soft tissues?

Osedax worms and other decomposers eat the whale’s bones, which weigh 10,800 kilograms. These decomposers consume the bones at a rate of 216 kilograms per year. How long will it take for the bones to disappear?

The trunk of a Douglas fir is 20,465 pounds. On average, 47.7 pounds will decay per year. How many years will it take to decompose?

A log of a western hemlock takes 273 years to decompose. Its rate of decay is 58.8 pounds per year. What was the log’s original weight?

It took 1 year for an elephant carcass to fully decay. It decayed at a rate of 35.6 pounds per day. What was the elephant’s original weight?

A group of elephants made 531 piles of dung in one location. These piles decayed at a rate of 0.0039 dung piles per day. How many years did it take for all the piles to decay?

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