Sarah Bedolfe
Blue whales are the biggest animals ever, but their dinner is not! They are filter feeders that prey on krill, tiny shrimp-like creatures.

Featuring one amazing marine animal per week.

The blue whale (Balaenoptera musculus) is the largest animal that ever lived. It is even more enormous than the dinosaurs that once roamed our planet.  The biggest one ever found was 33.5m (110 feet) long. A blue whale’s heart can be the size of a Volkswagen Bug and weigh up to 900kg (1900 lbs), and when it comes to the surface to breathe its spout can be nine meters (30 feet) high!

Blue whales are really a gray color with a mottled pattern – but they appear blue underwater, which is how they got their name. Photo courtesy of Rene Macare.

Blue whales occur in all oceans except the Arctic. There are multiple populations, as well as several subspecies, and the Antarctic blue whale is the biggest type. It is believed that most blue whale populations spend winter in warm temperate or tropical water where they mate and calf; they then migrate to the poles in summer, where they feed on krill. However, blue whales in the northern Indian Ocean seem to be non-migratory, staying in that area all year because there is enough food for them there.

A blue whale spout can be nine meters (30 feet) high. Photo by NOAA Photo Library via Wikimedia Commons, Creative Commons License. 

Blue whales may be the biggest animals, but their dinner is not! Blue whales are filter feeders that prey on krill, tiny shrimp-like creatures. Instead of teeth, blue whales have baleen plates – big bristles that filter water. They’re made of keratin, the same material that makes up your fingernails and hair. Like other baleen whales, blue whales have pleated throats that can expand. When it is feeding, a blue whale gulps a ton of water, expanding its mouth. It then uses its tongue to push the water back out through the baleen. While the water escapes, the baleen traps any food that was in the water so the whale can swallow it. How can the biggest animal on earth survive on such small food? A blue whale has to eat a lot of krill. In fact, it can eat 4 tonnes (8,800 lbs) of krill in a day!

Blue whales are listed by the IUCN as Endangered. Traditional whaling lacked the technology to take down blue whales because they were too big and fast. After industrial whaling with harpoon cannons came about at the turn of the 20th century, however, the world’s blue whale population was decimated. At the time, whalers called them sulphur-bottom whales because blue whales often had yellowish stomachs due to algae growth.

Whale watchers in southern California get a close look at a blue whale blowhole. Photo courtesy of Rene Macare. 

In 1966 blue whales were protected worldwide but since they have long lives and they grow and reproduce slowly, their recovery has taken a long time. Scientists are only just starting to see signs that they’re coming back.

Now one of the biggest threats blue whales, and other whale species, face is injury or death from accidental ship strikes. This is especially a problem where blue whale feeding grounds overlap with areas that have high shipping traffic. In the Indian Ocean, off the coast of Sri Lanka, several blue whales have died this way this year. Such incidents have occurred in San Francisco Bay as well. Fortunately, in response, shipping traffic around the Bay will soon be rerouted away from the whales to prevent these collisions.

Goodbye! A blue whale shows its fluke before heading down to deeper waters to feed on krill. Photo courtesy of Rene Macare. 


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