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Home > What Happens When a Whale Dies > Food for the Depths

What happens when a whale dies?
Food for the Depths

A whale is a huge animal—an adult blue whale can weigh up to 160 tonnes!

A whale carcass provides a feast for the animals in the area where it falls.

Whale bones on the ocean floor with hagfish swimming around them.

Whale bones on the ocean floor attract hagfish.

First Response Team: Hagfishes and Sharks

The first animals to arrive at a whale fall are the free-swimming animals because they can get there quickly. Such animals include hagfishes and sleeper sharks (Somniosus pacificus).

  • These fish eat 40 to 60 kg of meat a day—each!
  • At that rate, it can take four months to two years for the whale to be eaten.
  • For an adult blue whale, it can take close to five years!
  • These fish locate the carcass by smell
  • Other animals are also often found on whale falls, such as lysianassid amphipods and lithodid crabs.

Clean-Up Crew: Worms

Once most of the meat is gone, the first group of animals leaves and groups of smaller colonizers arrive.

These animals are smaller and will live on or around the whale carcass until the food is gone.

The majority of these animals are marine worms called polychaetes.

  • This stage lasts up to four and a half years—longer for an adult blue whale.
  • There can be 20 000 to 45 000 individuals per square metre during this stage.
  • This density of animals is the greatest ever found on any ocean floor.
  • In addition to polychaete worms, there are molluscs, crustaceans and bacterial mats. Bacterial mats are a thick layer of bacteria that cover the surface of the whale’s body.
  • This stage ends when the bacteria and other organisms use up all the available oxygen in the area.
An illustration of a whale fall.

A whale fall, showing worms and other marine creatures that feed on the carcass. Illustration by Michael Rothman.

Something from Nothing: Bacteria

Once the polychaetes finish, there is nothing left of the whale but its bones. But even the bare bones provide nourishment because they contain a lot of fat.

  • Anaerobic bacteria (bacteria that do not require oxygen) feed on the fat that remains inside the bones.
  • As they feed, these bacteria convert sulphate from sea water into sulphide.
  • Sulphide is energy rich and supports an entire food web of other animals.
  • This stage can last up to 80 years!
Whale bones on the ocean floor.

The yellow substance that covers these whale bones is a bacterial mat.

Useful Bones


Even when there is nothing left to eat on the whale carcass, the remains of the bones are still useful. They are used by filter-feeding animals as a sort of step-stool.


  • These animals attach themselves to the bones in order to get higher into the water current, where there is more food.
  • They use arm-like appendages to catch particles of food that float in the water.
  • This stage can last more than 100 years!

Building a Whale


Q: How do whale skeletons make it from the bottom of the ocean to a museum display?
A: Not all whales that die sink to the bottom of the ocean. Sometimes, if the conditions are right, a whale’s body will wash up on the beach.

When this happens, the whale’s body is often donated to a museum. It is cleaned and then the skeleton is buried so that the bacteria in the soil can clean it further.

After many years, the whale’s skeleton is brought to a museum where the cleaning job is finished up and the bones are reassembled.

Q: How do you clean the bones at the museum?
A: The blue whale skeleton that we are cleaning at the Canadian Museum of Nature for the new RBC Blue Water Gallery is being soaked in a bath of enzymes. Enzymes are a type of natural chemical that “eats” the oil contain in the bones. When the enzymes are done their job, we will wash the bones and let them dry.

Q: When can I see this blue whale?
A: The blue whale skeleton will be featured in the new RBC Blue Water Gallery at the Canadian Museum of Nature. The gallery opens in May 2010.

 

A collection technician adjusts a whale bone in its bath of enzymes.

Bones (the premaxillae) of a blue whale rest in a bath of enzymes that decomposes the oil in the bones.

 

 

 

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