Whales, dolphins and porpoises belong to the Order Cetacea.
There are over 90 species of whales, dolphins and porpoises (cetaceans) found throughout the world’s oceans. Of these, 53 species are known to inhabit Australian waters.
Following the decline of the dinosaurs more than 50million years ago, the evolutionary process of whales and dolphins began. Around 10 million years ago, most of the whales and dolphins that we know today were present.
There are two main types of cetacean: Odonotocetes or toothed whales and Mysticetes or baleen whales.
Sperm whales, killer whales, belugas, narwhals, beaked whales, dolphins, pilot whales, killer whales, porpoises and river dolphins belong to the Odontoceti whale group. These whales have a single blowhole, teeth and use echolocation to find their prey of fish and squid amongst others.
Dolphins are mammals; they breathe air and give birth to live young. Dolphins also have small hairs which grow on their rostrums.
Dolphins and whales have a layer of fatty tissue under the skin, called blubber which maintains the animals’ body heat. This layer of fat also provides an important energy source.
Dolphins and whales have very good eyesight both above and below the water.
External Features of a Dolphin (c) E. Hawkins 2010
Baleen whales are some of the world’s largest animals and are often called the ‘great whales’. The Blue whale is the world’s largest known animal reaching up to 33m in length.
Right whales, Bowhead whales, Gray whales, Fin whales, Sei whales, Bryde’s whales, Omura’s whales, Minke whales, Blue whales and Humpback whales all belong to the Mysticeti (baleen) whale group.
Right and bowhead whales lack a dorsal fin whilst other Mysticeti whales have their dorsal fin positioned behind the midpoint of their back.
These whales have a double blow hole, and an upper jaw hung with baleen (stiff plates of keratin with fringes inside) instead of teeth. They feed by gulping large amounts of water and prey when the whale brings its jaws together water is forced through the baleen fringes and out the sides of the mouth. Small schooling fish and invertebrates such as krill are captured during filtering and swallowed. Baleen whales may feed at the surface or in deeper water.
Most baleen whales make long-range seasonal migrations, moving toward high-latitude (polar) feeding areas in the summer and toward low-latitude (tropical) calving areas in the winter. Some individual whales do not migrate. These may be juveniles or post-reproductive adults that tend to stay in protected nearshore areas.
Northern and southern hemisphere populations of the same species don’t encounter one another due to the opposite seasons in the northern and southern hemisphere. While the northern population is foraging in polar feeding grounds during the northern hemisphere’s summer, the southern population is breeding and calving in tropical regions during the southern hemisphere’s winter.
Baleen whales can migrate 3,000 to 8,000 km each way, depending on the species.