What do whales busy themselves with? They certainly aren’t swimming around just waiting for humans to spot them: they have much more important things to attend to. The precise nature of their activity varies from species to species of whale, but they share certain behavioural traits.
Although whales sleep for approximately eight hours per day, scientists have discovered that the actual sleep process for whales is quite complicated. This is because they are mammals that live in water but breathe air by rising above the water surface. They can ‘hold’ a breath for a substantial time under water – in the case of the sperm whale, for around eighty minutes. Even so, they need to be aware of when to rise to the surface for air. Electroencephalograms (EEGs) have shown that one half of their brain ‘shuts down’ or sleeps, while the other half is still active and able to respond to the need for air, or to danger.
Not all whales eat the same food or find it in the same manner. Whales, depending on their size, may eat tiny marine creatures, for example krill, or creatures as large as octopus and even mammals such as walrus. There are two sub-species of whale – those with teeth and those without – and this determines how they feed.
Toothed whales often hunt and catch prey using a skill called echolocation. The whale produces clicking and buzzing noises, which travel through the water and bounce off objects in the vicinity. From the time the echo takes to return to it, the whale can gauge information about how far away the object is, how dense it is and whether it is moving or stationary. This helps the whale to decide whether the object is prey or nothing of interest.
Whales without teeth (baleen whales) use a method called ‘filter feeding’. A baleen whale swims with its mouth open, allowing water and creatures to enter, and the baleen bristles in its mouth act as a filter, catching the food before the whale expels the water with its tongue.
Whales are generally very social creatures, although some species of baleen whale are less so. Living together in groups known as ‘pods’, they exhibit a high degree of caring for others in the pod. For example, they seek to make sure every whale in the pod has food when they hunt, and they protect each other if danger threatens. This shows an instinct for securing the safety and survival of the whole group.
The term ‘whale song’ is familiar to most people; the ‘song’ is in fact the low-pitched set of noises which mainly baleen whales use to communicate with each other. Toothed whales often make high-pitched whistling and clicking noises to communicate.
As well as using sounds, whales communicate by body movements. They leap up out of the water, known as ‘breaching’, and lunge at the water, slapping the surface with their tails. They could be communicating a warning of danger, telling others of nearby food, making mating calls, or even just telling other whales they want to play. We cannot be entirely sure what a whale talks about – perhaps sometimes they are pointing out those strange humans in boats who are staring at them! Whatever they are saying, it makes for fascinating and exciting watching.