The biggest whales eat tiny animals called krill; a blue whale eats several tons of krill in a day. Estimates run from about 3 to 8 tons. Rorqual whales such as humpbacks, fins and blues feed by lunging: they gulp a huge mouthful of water and prey, then push the water out through the baleen. Baleen whales have no teeth in their mouths. Plates called baleen hang from the upper jaw; baleen plates work like a sieve: water goes out and food stays in. A bowhead whale has the longest baleen plates of any whale, about 3 to 4.5 meters (10 to 15 feet) long. A fin whale grows to roughly 65 to 85 feet long, second only to the blue whale in size; a gray whale feeds by sucking up mud from the sea floor and straining out food.
Humpback whales eat krill and small fish; humpback whales trap fish in bubble nets. They swim in a broad circle while breathing out, which makes a column of bubbles that bunches prey together. Sperm whales hunt deep in the dark, with dives to 2,000 feet or more for squid, sharks, skates and fish, and eat about 3 percent of their body weight a day. Fin whales eat krill, small fish and squid. A fin whale can eat up to 2 tons of food in a day; narwhals eat Arctic fish, squid and shrimp.
Killer whales, also called orcas, live in family groups called pods; orca society is matrilineal: young orcas always stay in their mother's pod. Orcas are top predators of the sea, and healthy adult orcas have no natural predators. Orcas in packs can hunt prey bigger than themselves, and a pod may team up to surround a blue whale; orcas click to echolocate, and they also rely on sound to feed, talk and find their way. Each orca pod has its own sounds, and the calls work like family badges. Beluga whales use their ears and sound to find their way and to hunt, because they can echolocate; as top predators, whales help keep ocean ecosystems in balance.
Whale bodies that sink to the sea floor are called whale falls. Scavengers strip the soft tissue in a matter of months; a dead whale on the sea floor feeds a whole community, from large scavengers to tiny bacteria. A dead whale's skeleton can feed deep-sea life for years or decades. A single whale fall can give the deep sea as much food as several thousand years of marine snow, the slow drizzle of dead material from above; Zombie worms of the genus Osedax, whose name means bone devourer in Latin, were first found on a whale fall in 2002.
Words to know
- krill: tiny sea animals
- sieve: a strainer
- lunging: a big gulp
- scavengers: dead-food eaters
