Their calls can be haunting. Their size can take your breath away. And their worlds are dark and quiet.

　　Whales!

　　There are many different species of these huge, warm-blooded, air breathing mammals that live in the sea. There is the blue whale and the killer whale, humpback and orca, just to name a few.

　　According to several science websites, whales live a long time. There are many different species of whales and each has a different lifespan. The average lifespan, however, is about 50 years.

　　In the wild whales live for a long time. Bowhead whales spend their lives in the cold Arctic waters. They may be the world's oldest mammals, living possibly more than 200 years!

　　As they lived, these giants of the sea die big. Before gases develop in the body, or carcass, of a dead whale it sinks to the ocean floor. This is called a "whale fall" and it supplies room and board, in other words food and shelter, to thousands of ocean creatures for many decades.

　　Scientists have only recently discovered just how many species live in a whale fall. This is mostly because whale falls are difficult to find in the ocean. It is like trying to find a needle in a haystack, as we like to say.

　　The first stage

　　The smell of the dead whale brings the first stage of feeders – the traveling, or mobile, scavengers. A wide variety of fish and sharks come from miles and miles to scavenge the dead whale's soft flesh or tissue. This phase can last as short as several months to as long as two years.

　　As you can imagine, these first stage scavengers are messy eaters. Their feeding frenzies leave a thick layer of pieces of the whale, what scientists call biomaterial, on the sea floor. This is when the dinner bell rings for the second stage scavengers.

　　The second stage

　　During the second stage of decomposition strange creatures appear. Shrimp-like creatures, crustaceans such as crabs and mollusks eat the small pieces of whale tissue that have dropped to the ocean floor.

　　Hairy worms are also part of this stage. They feed on the whale bones making the whale carcass look like a carpet – a moving, living carpet. This phase can last up to two years.

　　The third stage

　　The third and final stage is the longest. It can last for decades. The flesh of the whale has long been eaten. But even the bones support life.

　　As the whale bones decay, they produce sulfide, a type of gas. This gas supports a rich variety of life. Worms, mussels and several types of clams live off the gas that the whale bones give off.

　　Researchers found more than 30,000 animals totaling more than 200 species on one, single whale skeleton. Scientists who have studied the life of a whale fall found that the community of life and rare species of this final stage is larger than any known community on the deep seafloor.

　　I'm Anna Matteo.

　　Let us know what you think about this piece on Whale Falls in the Comments section or on 51VOA.COM. Or try using some of the scientific terms you learned in this story.

　　Enjoy this video made by Sweet Fern Productions showing the stages of a whale fall.

　　Anna Matteo wrote this story for VOA Learning English. Kathleen Struck was the editor.