Mammals that do not completely sleep
24-04-2012
When you think of mammals sleeping you probably imagine that they all sleep in a manner fairly similar to humans, though in fact, when you go beyond the easy assumption, you realise that while many do have similar sleep habits to humans there are a number of mammal species that have quite different sleep patterns and behaviours.
For example, whales and dolphins, two species that are close to humans in many senses, do not sleep like humans at all. The reason for this is the totally different environments that we live in. While humans live on land, dolphins and whales live in water. While humans live in an environment where they can breathe while asleep, cetaceans have to surface to breathe and the whole process requires them to be awake. This poses a serious problem for whales and dolphins, as all mammalian species need sleep, yet they can only hold their breath for around 30 minutes maximum. While they could survive on short naps, they have come up with a somewhat more extreme solution: only half their brain sleeps at one time.
That is right, whales and dolphins can be both awake and asleep at the same time. One half of their brain sleeps while the other stays awake. We have all had days where we feel like the same process has happened to us.
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