The porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are however distinct from dolphins, although the word "porpoise" is often used to refer to any small dolphin, especially in North America. A key difference is the shape of the teeth and of the head.
Porpoises, divided into six species, live in all oceans, mostly near the shore. Probably best known is the Harbour Porpoise, which can be found across the northern hemisphere.
Porpoises tend to be smaller but stouter than dolphins. They have small, rounded heads and blunt jaws instead of beaks. Their teeth are spade-shaped, whereas dolphins have conical teeth. In addition, a porpoise's dorsal fin is generally triangular, rather than curved like that of many dolphins.
These animals are the smallest cetaceans, reaching body lengths up to 2.5 m; the smallest species is the Vaquita, reaching up to 1.5 m.
Porpoises are predators hunting mainly fish, often also squid and crustaceans. Most common are small groups of up to ten individuals, which in some species may join forming aggregations of several hundred animals. Different click and whistle sounds are used for communication. Like all toothed whales they are capable of echolocation by means of ultrasound. Porpoises are fast swimmers—Dall's porpoise is said to be one of the fastest cetaceans with a speed of 55 km/h. Porpoises tend to be less acrobatic and more wary than dolphins.
Finless Porpoise, Neophocaena phocaenoides
Vaquita, Phocoena sinus
Harbour Porpoise, Phocoena phocoena
Burmeister's Porpoise, Phocoena spinipinnis
Spectacled Porpoise, Phocoena dioptrica
Family Physeteridae: Sperm Whale
dalli dalls porpoise