How Does Baleen Work?

What Is Baleen?

Baleen is a specialized structure of flexible parallel plates in the mouths of certain whales that the whales use to feed. Whales that have baleen are commonly referred to as baleen whales. Baleen lines the whale's mouth in place of teeth, and the parallel plates are covered with coarse hairs, which makes baleen look like a hairy comb. While baleen is sometimes called whalebone, it is not actually a bone or enamel like teeth; it is keratin, the substance that makes up hair and nails. Baleen whales include the humpback whale, the blue whale, the right whale and the fin whale.

How Baleen Whales Eat

When a whale feeds, its baleen acts as a giant strainer or filtration system to capture small aquatic prey such as krill, plankton and small fish. When a baleen whale feeds, it opens its mouth wide, often in a large school of plankton or krill, to allow a huge volume of water to enter, sometimes more than 10,000 gallons. It then shuts its mouth partway, closing gaps between its baleen that allowed the water and prey to enter, and forces the water back out. As the water rushes out through the baleen, the dense hairs keep the prey from leaving the whale's mouth. Each gulp of water can produce 25 pounds of krill and other food for the whale, but it requires significant effort for the whale to take in and strain water for food, so the overall energy gain can be small depending on the amount of prey in the water. As a result, baleen whales must often feed for several hours to consume enough calories to survive.

Baleen Whales vs. Toothed Whales

Toothed whales have teeth rather than baleen, and feed by biting, tearing and swallowing prey similar to the way human beings do. Toothed whales include sperm whales, killer whales, dolphins and porpoises. Unlike baleen whales, which capture small prey in large quantities, toothed whales tend to eat larger prey in smaller quantities. For instance, the sperm whale is known to feed on giant squid, which can be more than 40 feet long. Apart from differences in feeding habits, baleen whales tend to be much larger than toothed whales, (the sperm whale being an exception) and have a blowhole that consists of two openings instead of one. Baleen whales also tend to swim more slowly than toothed whales, which is due in part to the fact that they do not need to chase their prey through the water.