 rorquals  (family balaenopteridae) are the largest group of baleen whales, with nine extant species in two genera. they include the largest animal that has ever lived, the blue whale, which can reach , and the fin whale, which reaches ; even the smallest of the group, the northern minke whale, reaches . ==characteristics== rorquals take their name from french rorqual, which derives from the norwegian word rÃ¸yrkval, meaning "furrow whale". all members of the family have a series of longitudinal folds of skin running from below the mouth back to the navel (except the sei whale and common minke whale, which have shorter grooves). these are understood to allow the mouth to expand immensely when feeding, "permitting them to engorge great mouthfuls of food and water in a single gulp". these "pleated throat grooves" distinguish balaenopterids from other whales. rorquals are slender and streamlined in shape, compared with their relatives the right whales, and most have narrow, elongated flippers. they have a dorsal fin, situated about two-thirds the way back. rorquals feed by gulping in water, and then pushing it out through the baleen plates with their tongue. they feed on crustaceans, such as krill, but also on various fish, such as herrings and sardines. gestation in rorquals lasts 11â12 months, so that both mating and birthing occur at the same time of year. cows give birth to a single calf, which is weaned after 6â12 months, depending on species. of some species, adults live in small groups, or "pods" of two to five individuals. for example, humpbac
Baleen_whales