Baleen whales are whales that belong to the parvorder Mysticeti, one of the two in the infraorder Cetacea which comprise of whales, dolphins and porpoises. These whales, also called whalebone whales, are edentulous, meaning that they do not have teeth. Instead of teeth, they have baleen plates, which are special plates made of keratin that are used to filter food such as zooplankton from water.
Baleen whales are generally much larger than their toothed counterparts, with the blue whale being the largest animal ever to have existed, with adults being able to reach 30 meters in length. The oral cavities of these whales are specialized for filter feeding, meaning that the mandibular joints are extremely flexible.
This gives the whales the ability to dynamically enlarge their oral cavities in order to draw in enormous quantities of water with zooplankton, also making it possible to grow to titanic sizes. These whales must come to the surface to breathe air, and they do that through two blowholes compared to the one blowhole of toothed whales. The paired blowholes form the distinct V shape seen in surfacing whales. The Mysticeti comprises of four families, with notable species such as the blue whale, gray whale, humpback whale and minke whale, with the blue whale being the largest species and the minke being the smallest.
Dentition of baleen whales
These whales get their name from the baleen plates, an adaptation for filter feeding. The term comes from the archaic English term baleen which was used for whales, which comes
from the Latin balaena. These plates consist primarily of keratin, the protein present in hair and nails. These plates have “hairs” arranged like a comb which enables the whales to eject water while retaining zooplankton and fish. These whales have teeth only during their embryonic phase, and fossils of these whales were toothed, so the baleen plates must have evolved more recently.
Diet and feeding
Contrary to toothed whales, which catch their prey actively and individually, these toothless whales are carnivorous filter feeders. The preferred diet of baleen whales is krill, tiny crustaceans which made up significant amounts of zooplankton. Krill is mainly found in the Southern Hemisphere during summer, and Northern Hemisphere whales may feed on schooling fish or even organisms living in shallow waters on the bottom of the seabed such as amphipods.
Reproduction and life cycle
Most toothless whale species reach sexual maturity at 5 to 10 years. Females usually give birth after 7 to 11 months of gestation and may feed the calf for up to a year. Before they become adults, these whales grow in size and weight at remarkable rates. Blue whale fetuses can add up to 100 kilograms per day, while, during suckling, they can add 80 kg per day and reach 17 tons and reaching 13 to 16 meters before weaning. When reaching adulthood, they will be 20 to 24 meters long and weigh up to 180 tons. Baleen whales can live for 80 or even 90 years.