Dolphins Whales and Porpoises: Cetacea

Cetaceans generally have pregnancies that last ten to sixteen months. Like all mammals, they nurse their young. The young tend to stay with their mothers for at least a year and often much longer. Many cetaceans give birth only every two to five years. These animals do not become capable of reproducing for about three to ten years. Large whales may live for close to 100 years and are slow to mature.

Cetaceans have evolved a wide spectrum of behaviors. Some species such as the spinner dolphin are known for the way they leap out of the water, while other species, like almost all porpoises, rarely jump when they come to the surface. Some members of this order live in groups of up to one thousand, while others live in groups of ten or fewer animals. Some groups show great social stability and communication. Killer whales, for example, are known to hunt in packs. Other social groups are simply casual associations, with members coming and leaving at will. Communication seems to involves several different types of sounds combined with echolocation.