Feeding

What do whales eat?

There are two major groups of whales: baleen whales (also known as mysticetes) and toothed whales (also known as odontocetes). Each of these two whale types has its own specific way of feeding.

Eating through one's moustache

Baleen type whales include the largest animals on the planet, yet they feed mainly on tiny organisms such as zooplankton (crustaceans, such as krill, and copepods) and small fish (capelin, herring, sand lance, etc.). They use their baleen plates like sieves to filter water and retain prey.

Each baleen plate is composed of a number of rigid hairs sandwiched between two plates made of a hard, yet flexible material. A baleen plate could be likened to two enormous fingernails stuck together with cat's whiskers in between. Baleen plates are positioned in the mouth like vertical blinds suspended all along the upper jaw. Baleen whales will have between 150 and 400 baleen plates suspended from each side of the upper jaw, depending on the species. Like our fingernails and hair, baleen plates grow, and wear, continuously. The plate edges that rub against the tongue wear faster than the hairs they contain. This results in the hairs extending beyond the baleen plate "sandwich". The fringe of hair thus formed becomes matted and serves as a filter that, while allowing water to flow through easily enough, efficiently retains prey. The scientific name for this group of whales is derived from the baleen plates; mysticete is Greek for "moustached whale"!

Baleen whales are known to use three different general feeding strategies. Some species are "engulfers". They feed by engulfing large quantities of water and prey with each enormous mouthful. The water is then expulsed while the prey is retained and then swallowed. Whales that engulf their prey possess ventral grooves, or folds of skin, that enable the throat to expand like an accordion allowing them to scoop up impressive volumes of water. These are commonly known as "rorqual" whales, from a Norwegian term meaning "pleated whales". Right whales, on the other hand, are "skimmers". They do not possess ventral grooves. Instead of engulfing large volumes of water at a time, they simply swim along with their mouths wide open, filtering water as they go and capturing tiny crustaceans known as copepods. Grey whales are usually "excavators". They use their short baleen plates to filter sediment on the ocean floor and capture small organisms that live buried therein. Their technique consists of diving to the bottom, turning sideways and using suction on the sea floor to draw in small organisms. This species also feeds on schools of small planktonic crustaceans, fish, squid or crab larvae by either skimming or engulfing.

Odontocetes bite into life!

Odontocetes include sperm whales, killer whales, dolphins and porpoises, among others. They use their teeth to capture prey that consists mainly of fish and squid, which they swallow whole. Beluga whales also seek out animals that live on the sea floor, such as worms and shellfish. Certain groups of killer whales actually feed on other marine mammals such as seals and sea lions. They have even been known to attack whales much larger than themselves.

There are approximately 70 species of toothed whales in the world. The number of teeth they possess varies from species to species. Some dolphins have more than 160 teeth. However, females of certain species of beaked whales never grow teeth. The sperm whale is the largest of the toothed whales. It possesses between 30 and 60 teeth that develop exclusively in the lower jaw. Tooth shape and size are generally the same for all representatives of a given species. Interestingly enough, teeth are not absolutely essential. Whales have been discovered with teeth that had either fallen out or been worn down. Others, found with broken jaws, were still able to feed. The largest whale tooth belongs to the male narwhal. Its long tusk is in truth the upper left canine. It grows in a spiral fashion and pierces the upper lip. It can grow to 2.7 m in length. This tooth is not used for feeding. More likely it is used to establish hierarchy between males during the mating season.

Due to the fact that the prey sought by toothed whales is often larger and more mobile than what is sought by baleen whales, their feeding techniques require more co-operation and learning. This likely explains why toothed whale offspring generally stay with their mothers longer than the offspring of baleen whales. Also, many toothed whale species have complex social structures. Populations of killer whales that feed on fish around Vancouver Island, for example, are composed of family groups centred on the mother. Matriarchs of this species spend their entire lives surrounded by their own, as well as their daughters' offspring.

It is clear that feeding has a major influence on how whales live. It can determine how groups are formed, migration patterns, care given to offspring and many other aspects of whales' lives, be they baleen whales or toothed whales. It is important to note that whales do not eat algae and that no species of whale preys on humans!

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Three St. Lawrence rorqual whales, three different strategies