Echolocation in killer whales
Sperm whales have the most powerful biosonar, and can create bursts of sound louder than a NASA rocket launch. The world’s largest predators, the largest toothed whales, and the deepest-diving air breathers, sperm whales catch prey in cold, crushing dark, routinely diving to 400 metres for periods of 35 minutes. When beginning a dive, a sperm whale first emits regular clicks, which provide long-range information about prey. As it dives deeper, the clicking becomes steadily more rapid until, when the sperm whale is about to catch a squid, it forms a continuous buzz.
Intelligence is another important trait of toothed whales. Their brains are relatively large for their body size, and used for complex brain functions, including biosonar. Whether large brains came about because of biosonar and the sophisticated sensory processing required to use it, or vice versa, is still unclear.
The killer whale, or orca, is a highly successful predator, feeding on fish, seals and even other whales. IMAGE: MONIKA WIELAND/SHUTTERSTOCK
Complex social behaviour is another sign of odontocete intelligence, as killer whales,Orcinus orca, clearly show. Their social groups, called pods, are organised around mothers and their descendants. These strong mother–calf associations may last an entire lifetime, an unusually close bond in nature.
Like people, killer whales (also called orcas) are self-aware, learn quickly, innovate, and have a suite of behaviours that they transmit to one another (culture). This affects what they eat, what they do for enjoyment, and even their choice of mates. Usually this behaviour is modelled by older orca females on younger animals. A mother orca, for example, will hold a Chinook salmon in her mouth so that her calf can chew on it, communicating her preference for this salmon species to the next generation. Some orca pods, which contain up to 50 animals, have their own unique groups of calls, distinctive enough that scientists can recognise a pod by its call alone.
Killer whale (Orcinus Orca), named Old Tom, swimming alongside a whaling boat in pursuit of a whale calf. C. E. Wellings, Whaleboat fast to a whale, Twofold Bay (detail) c. 1900–1922, nla.pic-vn3103733. Courtesy National Library of Australia.
Orcas also use complex, coordinated group hunting behaviour, especially evident when preying on other sea mammals. In Eden, New South Wales, killer whales even cooperated with human whalers, including Indigenous people, to hunt baleen whales. The orcas would alert the whalers when whales were present and lead them to their quarry. In return, the whalers let the orcas eat the tongues from dead harpooned whales.
Untitled painting by Bronwyn Bancroft depicting six men on a timber boat towing a whale, while other whales swim nearby. Artwork by Bronwyn Bancroft, ANMM Collection. It is the fourth in a set of ten paintings that illustrate Percy Mumbrella's book 'The Whalers', about the relationship between indigenous whalers around Eden, New South Wales, and the killer whales who led them to their prey
Baleen, biosonar and big brains are adaptations that probably helped drive cetaceans’ spectacular diversification between 23 and five million years ago. Though descended from a common ancestor and roughly the same shape, today’s cetacean species are diverse, feeding on different prey and using different hunting techniques. We now know of around 90 species of whales, dolphins and porpoises, but we keep adding new ones to their ranks as discoveries are made. In February 2014, scientists confirmed a new species of beaked whale: the six-metre hotaula, Mesoplodon hotaula, an elusive, deep-diving relative of the sperm whale.
