There are 77 species of whale, dolphin and porpoise. They are the only aquatic mammals to spend their entire lives in water. All are streamlined animals with strong, horizontally set tail flukes.
Their front limbs are modified into flippers and there are no visible hind limbs. As a general rule, whales produce only one young at a time, although twins are known.
There are two groups within the order. First, the toothed whales, with 67 species of small whale, dolphin and porpoise, all of which prey on fish and squid. To help locate their prey, they use a form of ultrasonic sonar: they emit high-frequency clicking sounds which bounce off objects, the echoes informing the whale with astonishing accuracy of the size, distance and speed of travel of the object. All of these whales have teeth, some a pair, some as many as 200.
In the second group are the 10 largest whales, known as the baleen whales. These marine giants feed on tiny planktonic animals, which they extract from the sea by filtering water through plates of fringed horny material hanging from their upper jaws. These baleen plates, as they are called, act as sieves to trap the plankton. There are 3 families of baleen whale: rorquals, gray and right whales.
Phocoenidae: Porpoise Family
Although the name porpoise is sometimes erroneously applied to members of other families, strictly speaking, only the 6 members of this family are porpoises. They are small, beakless whales, rarely exceeding 7 ft (2.1 m) in length, and usually with prominent dorsal fins. They have 60 to 80 spatular teeth and feed mainly on fish and squid.
Porpoises live in coastal waters throughout the northern hemisphere, often ascending the estuaries of large rivers. One species, the spectacled porpoise, Phocoena dioptrica, occurs off the coasts of South America.
Range: Temperate N. Pacific Ocean.
Habitat: Inshore and oceanic deeper waters.
Size: 6 - 7 1/2 ft (1.8 - 2.3 m).
Dali’s porpoise is larger and heavier than most porpoises. Its head is small, and the lower jaw projects slightly beyond the upper. It lives in groups of up to 15, which may gather in schools of 100 or more to migrate north in summer and south in winter. It feeds on squid and fish, such as hake, and most probably uses echolocation when hunting.
Pairs mate at any time of the year, and the young are suckled for as long as 2 years.
These porpoises are rarely seen because they spend most of their time far from land. Most often they are spotted when they stray into coastal waters, especially along the Atlantic coast of South America. Spectacled porpoises are also seen around New Zealand in the south Pacific.
The back of this porpoise is black, while the underside and most of the face is white, except for the black around the eyes, which makes the animal look as though it is wearing spectacles -hence its name.
Spectacled porpoises dive down into deep water to catch large fish and squid. They tend to feed in cold-water areas, such as in the currents that travel up from the Antarctic. Like most porpoises, they have fewer teeth than dolphins, but each tooth is large and chisel-shaped. This allows the porpoise to catch larger fish than dolphins. In shallower waters, the spectacled porpoise also eats crabs, lobsters and other crustaceans. It is sometimes preyed on by orcas (killer whales).
Spectacled porpoises are mainly solitary, and do not travel in large groups, although two or three individuals are occasionally seen together.
Distribution: South Atlantic, Pacific, and Indian oceans.
Habitat: Deep ocean.
Food: Fish, squid, and crustaceans.
Size: 1.8 - 2 m (6 - 6.5 ft); 55 - 115 kg (121 - 253 lb).
Maturity: About 5 years.
Breeding: Single young born in spring.
Life span: 20 years.
Status: Data deficient.