Gliding gracefully through the marine waters, the blue whale is considered to be the largest creature to have ever existed. This behemoth can reach up to 110 feet long and weigh over 160 tons. Almost 30% of its weight is composed of blubber alone. Their massive energy requirements necessitate the consumption of vast amounts of food every day. But what do blue whales eat?
What Does a Blue Whale Eat?
The blue whale can be found feeding and traveling across all of the world’s oceans except for the extreme Arctic North. 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 grow no larger than an inch long. However, a few species can grow up to 3 or 4 inches. While they can be found all over the world, krill are particularly populous around the waters of Antarctica.
Blue whales have a highly specialized diet to which they’re well-adapted. As a result, they feed on remarkably few food items. Here are some of the most common foods in the blue whale’s diet:
- Krill
- Plankton
- Fish
- Other small crustaceans, such as copepods and amphipods
How Much Do Blue Whales Eat?
The blue whale’s diet consists almost entirely of krill.
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It’s estimated that the blue whale will consume up to 35,000 pounds of krill per day during peak feeding season. That’s around 10% of their entire body weight. Some sources estimate that it requires 2,200 pounds of food to fill the blue whale’s stomach. The whales maximize foraging opportunities and energy intake by feeding on as many krill as possible in a single trip. As noted above, marine animals, including fish, zooplankton, and small crustaceans, make up a relatively small part of their diet.
Female blue whales are generally larger than males and therefore require more food. Plus, after mating in the winter, they’re pregnant for the next 10-12 months. So, they must eat for the unborn calf as well. A blue whale calf drinks between 50-100 gallons of milk per day. It takes another 6-7 months after birth before the calf is fully weaned and begins to forage for itself. The high fat content of the mother’s milk, which can be up to 50%, enables the calf to grow very rapidly. The calf is thought to consume hundreds of pounds of milk per day.
What Makes Baleen Whales Different?
The blue whale is part of a group of cetaceans known as baleen whales. This group also includes minke whales, sei whales, and fin whales, among others. 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 our hair and nails. The plates 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 information about the whale’s life. By examining the chemical composition of the baleen, scientists can determine the whale’s hormonal levels or where it has traveled.
It’s estimated that a normal adult blue whale has around 300 to 400 baleen plates on each side of its upper jaw. These are complemented by various throat pleats, or grooves, that enable the mouth to expand outward like a balloon during feeding. 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 to the massive sizes they are today.
Blue Whale Feeding Mechanics
Blue whales have 300 to 400 baleen plates on each side of their upper jaws.
©bekirevren/Shutterstock.com
The blue whale’s feeding habits depend on locating scattered patches of food in the ocean. It makes multiple foraging trips per day. These whales sometimes dive to depths of a thousand feet or more in search of food.
When approaching a large, concentrated school of prey, the whale will begin to accelerate up to 20 mph and then lunge forward. The expanding throat pleats allow the whale to open its mouth to almost 90 degrees. The whale takes in a huge quantity of water in a single gulp, estimated to be over 20,000 gallons. The baleen plates, with the help of the tongue, then force the water back into the ocean while the prey remains trapped in the whale’s mouth.
The Connection Between Migration and Diet
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 in the winter, when they do most of their breeding. Unlike other species, however, the blue whale’s migratory movements are not fixed. Some blue whales may undertake only a partial migration, while others remain in the same area all year round. Their migratory patterns appear to be based primarily on food availability.
In addition to this seasonal migration, the evidence also suggests that blue whales complete a daily “vertical” migration. The whale moves from shallow to deep water and back again as their prey moves throughout the water column. This means they’re changing positions constantly throughout the 24-hour period.
