On the whales’ menu
Whether toothed whales or baleen whales, feeding influences group formation, migration, care provided to their young and many other aspects of cetacean life. It should be noted that no species of whale feeds on algae, and none preys on humans either!
Eating with its moustache
Baleen whales, which are amongst the largest animals on the planet, feed mainly on small organisms such as zooplankton (crustaceans such as krill and copepods) and small fish (capelin, herring, sand lances, etc.). These whales use their baleen like a sieve to filter out the water and retain their prey. Baleen consists of two hard plates sandwiching a series of very hard bristles. Baleen plates can be compared to two fingernails glued together with cat whiskers between the two. The baleen is arranged like vertical blinds across the upper jawbone. Depending on the species, baleen whales have between 150 and 400 baleen plates on each side of their mouth. Baleen, similar to human nails and hair, grows and wears continuously. On the baleen facing the inside of the mouth, the hard plates wear more quickly than the bristles, causing the latter to stick out from the “sandwich”. The bristles that stick out intertwine and form a filter through which water can easily flow, but which is efficient in retaining prey. Interestingly, whales of this group owe their scientific name to their baleen: Mysticeti translates as “moustached whale”!
At birth, whale calves have short baleen or no baleen at all, which facilitates nursing. The baleen develops slowly and begins to be functional at weaning, which is between 6 and 12 months depending on the species.
Baleen of all sizes
Baleen measures one metre in adult blue whales, compared to 90 cm for fin and humpback whales, and 30 cm for minke whales. The bowhead whale holds the title for the longest baleen, at over 4 metres. Baleen is generally brown or black except in the minke whale, where it is cream-coloured.
Gulper, skimmer or bottom feeder
Some baleen whales are “gulpers”, meaning they engulf huge quantities of water and prey at once before filtering out the water and swallowing the food. These whales have ventral grooves which allow the throat to expand like an accordion to take immense volumes of water into their mouths. These whales are known as “rorquals”, a Norwegian term that means “furrow” or “tube” whale. Right whales, on the other hand, are “skimmers”. They lack ventral grooves. Instead of engorging great quantities of water in one gulp, they swim with their mouths wide open, filtering the water as they go and capturing tiny crustaceans called copepods. The gray whale is generally a “bottom feeder”. It uses its short baleen to filter sediment on the ocean bottom and capture the creatures that live buried therein. Its technique consists of diving to the bottom, rolling onto its right side and sucking silt and mud from the seabed to feed on small organisms.
Odontocetes sink their teeth into life!
Toothed whales include notably sperm whales, killer whales, belugas, dolphins and porpoises. They use their teeth, all of which are identical, to capture their prey, generally fish and squid, which they swallow whole. The beluga also seeks out organisms living on the seabed such as worms and shellfish. Some pods of killer whales not only feed on marine mammals such as seals or sea lions, but even whales larger than themselves.
Teeth: plentiful or absent, small or large
There are approximately 70 species of toothed whales, the number of teeth of which varies from one species to another. Certain species of dolphins have over 160 teeth; in some species of beaked whales, however, the teeth of females will never develop to protrude out of the gums. The sperm whale is the largest of the toothed whales; it has between 30 and 60 teeth, which develop on the lower mandible only. Teeth do not seem to be essential however, as whales have already been found with missing or severely worn teeth, or with fractured jaws, but which were nevertheless able to feed. The largest whale tooth is found in the male narwhal: its long tusk is actually the upper left canine growing in a spiral, piercing the upper lip and reaching up to 2.7 metres long. This tooth, which serves no purpose for feeding, is believed to be a secondary sexual characteristic or a sensory organ.
Steep learning curve
Because they target prey that tend to be larger and more mobile than those preferred by baleen whales, toothed whales generally have feeding techniques that take longer to learn and require greater cooperation. This is undoubtedly why, generally speaking, young toothed whales stay with their mother longer than baleen whales. Further, numerous species of toothed whales have a complex social structure.