What Do Blue Whales Eat?

Written by AZ Animals Staff
Published: October 30, 2021
Image Credit iStock.com/MR1805
Share this post on:

Gliding gracefully through the marine waters, the blue whale is considered to be the largest creature to have ever existed. This massive behemoth can reach up to 110 feet long and weigh up to 150 tons. Almost 30% of this weight is composed of blubber alone. Their massive energy needs require them to consume vast quantities of food every day. The blue whale can be found feeding and traveling across all of the world’s oceans except for the extreme Arctic north. Once nearly hunted to extinction for its resources, the blue whale is now making a small comeback, though population numbers haven’t yet recovered fully from their lowest point. One of its most pressing future challenges is climate change, which could affect its feeding habits in many unpredictable ways.

What Does the Blue Whale Eat?

What Do Blue Whales Eat
The blue whale’s diet consists almost entirely of krill, but they also eat a small percentage of copepods and fish.

A-Z-Animals.com

The blue whale’s diet consists almost entirely of krill. These are small marine crustaceans that look a bit like shrimp. Most species of krill (there are nearly a hundred) grow no larger than an inch long, but a few of them do grow up to 3 or 4 inches. They occupy a very important place near the bottom of many marine food chains; they consume small algae and plankton in the water and are likewise preyed upon by larger organisms such as whales and fish. In essence, krill are an important intermediate link that transfers energy further up the food chain. While they can be found all over the world, krill are particularly populous around the waters of Antarctica.

It’s estimated that the blue whale will consume up to 6 tons (that’s 12,000 pounds) of krill per day. That’s around 4% of their entire body weight. The whales maximize foraging opportunities and energy expenditure by feeding on as many krill in a single trip as possible. Other marine animals, including fish, zooplankton, and other small crustaceans, make up a relatively small but significant part of its diet.

Female blue whales are generally larger than males and therefore require a bit more food consumption. After mating in the winter, they’re pregnant for the next 10 to 12 months and must eat for the unborn calf as well. It takes another six or seven months after birth before the calf is fully weaned from the mother’s milk and begins to forage on krill for itself. The exceptionally high-fat content of the mother’s milk enables it to grow very quickly. The calf is thought to consume hundreds of pounds of milk per day.

How Do Blue Whales Get Enough to Eat?

The blue whale is part of a major group of cetaceans known as the baleen whales (which also includes the minke whale, Sei whale, fin whale, and other close relatives). The name comes from the presence of unique filaments called baleen plates suspended from the roof of the mouth. As opposed to teeth, the baleen plates are composed of the protein keratin, the same substance as hair, horns, and nails. They grow continuously throughout the whale’s life, eroding at one end while growing at the other; a single sheet can contain around 15 years’ worth of the whale’s life. By examining the chemical composition of the baleen, scientists can even understand important information about the whale’s hormonal levels or where the whale has traveled.

It’s estimated that a normal adult blue whale has around 270 to 400 baleen plates situated around its mouth. These are complemented with various throat pleats (or grooves) that enable the mouth to expand outward like a balloon while taking in vast quantities of food. Scientists believe that the baleen plates evolved gradually starting around 30 million years ago as competition between toothed whales became fierce and new food sources became available. Massive plankton blooms from nutrient upwelling in the deep ocean starting about three million years ago may have enabled baleen whales to grow in size to what they are today.

The blue whale’s feeding habit depends on finding these disconnected patches of food in the ocean. It makes multiple foraging trips per day, sometimes diving up to depths of a thousand feet or more in search of food to consume. When approaching a large, concentrated school of prey, the whale will begin to accelerate its speed (up to 20 mph) and lunge forward. Its mouth then opens at a remarkably wide-angle, around 80 to 90 degrees, and takes in a huge quantity, perhaps around 200 tons, of water in a single gulp, thanks to the expanding throat pleats. The baleen plates will then squeeze out the water back into the ocean with the help of the tongue, while the prey remains safely within its mouth.

Blue whales spend most of the summer months feeding in polar waters. As winter approaches, they undertake a very long migration to equatorial waters. It’s estimated that their feeding rate is higher in the summer than the winter when they do most of their breeding. Unlike other species, however, the blue whale’s migratory movements are not set in stone. Some blue whales may undertake only a partial migration, while others remain within the same place all year round. Their migratory patterns appear to be based mostly on food availability.

In addition to this seasonal migration, the evidence also suggests that blue whales complete a daily “vertical” migration from shallow to deep waters and back again as their prey moves throughout the water column. This means they’re changing positions constantly throughout the 24-hour period.

What do blue whales eat
Blue whale underwater, close to the sea surface, chasing a school of fish with an open mouth.

bekirevren/Shutterstock.com

What do blue whales eat besides krill?

They consume fish, plankton, and other tiny crustaceans (like copepods and amphipods) floating in the water.

Do blue whales eat plankton?

Yes, they consume any zooplankton (very small and simple marine organisms) that gets caught up in their mouths. Some are so small that they might be filtered out, but larger zooplankton may remain.

A Complete List of the Top 5 Foods the Blue Whale Eats

Blue whales have a highly specialized diet for which they’re well-adapted. As a result, they feed on remarkably few food items. Krill is by far the most common food. Other prey tends to get consumed along with the krill.

Next Up: Types of Pointer Dogs

Share this post on:
About the Author

AZ Animals is a growing team of animals experts, researchers, farmers, conservationists, writers, editors, and -- of course -- pet owners who have come together to help you better understand the animal kingdom and how we interact.

More from A-Z Animals