The meat, blubber and oil of cetaceans have traditionally been used by indigenous peoples of the Arctic.Cetaceans have been depicted in various cultures worldwide.The extinct ancestors of modern whales are the Archaeoceti.
The baiji (Chinese river dolphin) has become "Possibly Extinct" in the past century, while the vaquita and Yangtze finless porpoise are ranked Critically Endangered by the International Union for Conservation of Nature.
Besides hunting, cetaceans also face threats from accidental trapping, marine pollution, and ongoing climate change.
Most mysticetes prefer the food-rich colder waters of the Northern and Southern Hemispheres, migrating to the Equator to give birth.
During this process, they are capable of fasting for several months, relying on their fat reserves.
They feed largely on fish and marine invertebrates; but a few, like the killer whale, feed on large mammals and birds, such as penguins and seals.
Some baleen whales (mainly gray whales and right whales) are specialised for feeding on benthic creatures.Male cetaceans typically mate with more than one female (polygyny), although the degree of polygyny varies with the species. Male cetacean strategies for reproductive success vary between herding females, defending potential mates from other males, or whale song which attracts mates.Calves are typically born in the fall and winter months, and females bear almost all the responsibility for raising them.Mothers of some species fast and nurse their young for a relatively short period of time, which is more typical of baleen whales as their main food source (invertebrates) aren't found in their breeding and calving grounds (tropics).Cetaceans produce a number of vocalizations, notably the clicks and whistles of dolphins and the moaning songs of the humpback whale.The two parvorders, baleen whales (Mysticeti) and toothed whales (Odontoceti), are thought to have diverged around thirty-four million years ago.