The biggest animals ever to live eat by straining the sea through their mouths
The blue whale can reach 31 metres and 190 tonnes, larger than any animal known to have existed, and it lives on some of the smallest prey in the ocean. Like the other 15 baleen whale species, it has no teeth for chewing, only fringed plates of whalebone that sieve plankton out of seawater.
Baleen whales, the Mysticeti, parted ways with toothed whales around 34 million years ago. Whales were once thought to descend from an extinct group of hoofed predators, but molecular evidence places them firmly among the even-toed ungulates, the group that includes hippos and deer. Four living families remain: right and bowhead whales, the rorquals, the gray whale and the pygmy right whale, the smallest at about 6 metres and 3,000 kilograms.
Body shape follows feeding style. Rorquals, such as the fin whale, are streamlined lunge-feeders built to accelerate, and the fin whale has been clocked at 10 metres per second. Right whales have huge heads and thick blubber and skim slowly through swarms of prey. Gray whales specialise in crustaceans on the seafloor. All share fused neck bones that stop them turning their heads, two blowholes and an insulating layer of blubber, and most prefer cold polar waters.
Their family tree keeps being redrawn. The pygmy right whale, despite its name, is genetically closer to rorquals and gray whales than to right whales, and a 2012 study of its bones moved it into a family otherwise known only from fossils, making it a kind of living fossil. The same year, a review led by Alexandre Hassanin proposed splitting the rorquals into four genera.
Males usually mate with several females, some competing through song, and mothers raise the calves alone, often fasting through long migrations. Arctic peoples have long used whale meat, blubber, baleen and oil. Commercial whaling pushed many species down until international law protected them, and numbers have since recovered, though the North Atlantic right whale remains critically endangered and pollution and ocean acidification add new pressure.
Source: Baleen whale
