What is a whale?
Whales belong to a group of mammals called cetaceans, which also includes dolphins and porpoises. Most people call the larger cetaceans whales, and the smaller ones dolphins. However, some species that we call whales actually belong to the dolphin family. In New Zealand there are five such whales: the killer whale (orca), short-finned pilot, long-finned pilot, false killer and melon-headed whales.
New Zealand whales
Almost half the world’s approximately 80 species of cetaceans are found in New Zealand’s waters. This is not surprising as New Zealand controls the fourth largest marine territory in the world, its waters are rich with foods that these mammals need, and it is on the migratory path of the largest whales.
Of the 38 cetaceans known to inhabit New Zealand waters, 22 are whales, but only a half dozen are relatively common. Some species, such as sperm whales, are highly visible and attract thousands of tourists to towns like Kaikōura. Others, such as beaked whales, are rarely seen and are known only because they beach themselves when injured or ill.
All whales are long and streamlined. They lack external hind limbs but have powerful tails that provide propulsion. Often they lift their tails above the surface before diving – an action known as fluking.
Whales also have a layer of fat under the skin known as blubber, which can be up to 50 centimetres thick. Blubber stores energy and insulates the whale from the cold in deep water. It is thought that whales live for 30 to 80 years.
Whales evolved from land-based mammals. At some point they became aquatic, but like all mammals they still breathe air, give birth to live young and feed their calves with milk. New Zealand has a fossil record of early baleen whales going back 35 million years, and early examples have been found in the Waitaki Valley, north Otago.
There are two types of whale: baleen and toothed.
Baleen whales have long bristle-fringed plates, known as baleen, which are made of keratin (a protein also found in human hair and fingernails) and fixed to the roof of the mouth. These sieve the minute crustaceans, such as krill, that they feed on. Baleen whales have two blowholes. And unlike some other whales, they do not use echolocation (emitting sounds to locate solid objects).
Baleen whales include the largest animals ever known. Greatest of all is the blue whale; the heaviest ever recorded was a female of 190 tonnes. Baleen whales migrate through New Zealand waters on their way south to feed on krill, which are abundant in the Southern Ocean. Of the world’s 13 species of baleen whales, eight are known in New Zealand, but only two, the southern right whale and Bryde’s whale, breed in New Zealand waters.
Toothed whales have teeth, rather than baleen, and a single blowhole. They find their prey through echolocation, emitting a series of clicks that travel through the water until they meet an object and are reflected back. By using a range of frequencies the whale can make a detailed examination of the object. Some scientists have suggested that the clicks may stun the prey. Toothed whales include sperm whales, which are relatively common around New Zealand, and the much rarer beaked whales, which have a small head with a beak and a bulging forehead.