Whales Swallow Half a Million Calories in Single Mouthful

The filter-feeding strategy of blue whales, the largest animals on Earth may explain their enormous size, according to a study that determined a single mouthful of food can contain 457,000 calories, or 240 times as much energy as they burn when grabbing that mouthful.

Blue and some other whale species eat by taking enormous mouthfuls of water and filtering out their meals, often tiny crustaceans called krill, using plates of baleen made of keratin, a protein found in hair, fingernails, and feathers.

The baleen whales are much more efficient feeders than their smaller relatives, the toothed whales, which hunt down individual prey and also baleen whales' efficiency is unprecedented in the animal kingdom.

When they take a gulp of water, they are filling their mouths with the amount of water equal to their own body mass, so there is nothing that comes close to doing that. These whales may eat an enormous quantity of food in a single gulp, but the effort is taxing. 

As the animals dive, they lunge into a school of krill, and their mouths open to 80 degrees and inflate like a parachute as water gushes in. This creates drag, slowing the whale. Whales can make up to six lunges in a dive. The calculated that the whales spent as much as 8,071 kilojoules (1,900 Calories) on a single lunge.

The measured of the jawbones of whales that made in museums to estimate the volume of the whales' mouths and the combination with krill densities to determine how much energy the animals captured in one mouthful. The answer is up to 1,912,680 kilojoules (about 457,000 Calories). They are doing something that is energetically very expensive, but they are getting an enormous payoff.