How the Wild Things Sleep

Most living creatures sleep — but why? Scientists explore big ideas about shut-eye.
Credit: olga_gl/iStock
Available on CBC Gem

How the Wild Things Sleep

Nature of Things

Most living creatures engage in some form of sleep.

Countless studies illustrate how animals adapt sleep for their own particular needs. Primates, elephants, marine mammals, insects, birds — even our own pet dogs and cats — all sleep differently. Even very simple organisms that lack a brain and central nervous system practise a version of sleep.

It appears sleep is essential behaviour for most living things — but why? What is the biological purpose of sleep? How the Wild Things Sleep, a new documentary from The Nature of Things, peers under the covers of the wonderful world of slumber to reveal some surprising answers.

It doesn’t take much to convince humans we need our sleep. Anyone who’s had a bad sleep knows what it’s like to be sleep-deprived: we’re clumsy and irritable; we’re forgetful; we suffer from brain fog.

The same appears to be true of our closest relatives: the great apes. At the Indianapolis Zoo, University of Toronto anthropologist David Samson demonstrates the link between the quality of an orangutan’s sleep and its ability to perform cognitive tests. We also learn that orangutans, much like humans, go to surprising lengths to make comfortable beds for themselves.

For bees, whose brains are completely different from those of mammals, getting the right amount of shut-eye is critical to the success and prosperity of the hive. Entomologist Barrett Klein in Wisconsin shows the fascinating world inside the beehive and what happens to the colony when bees don’t get enough sleep.

It’s a different story for wild elephants: they are almost constantly on the move. How the Wild Things Sleep features Prof. Paul Manger, a leading expert on elephant brains from the University of the Witwatersrand, Johannesburg. He describes the surprisingly short sleep cycles for these giants, who on average sleep about two hours a night. If their nightly sleep is disturbed — by predators, for example — they don’t need to catch up like we do.

Other creatures have evolved with the extraordinary ability to sleep with one half of their brain, while the other hemisphere stays awake.

Fur seals have mastered this trick. They can spend weeks out at sea, getting sleep whenever they need it but always keeping an eye out for danger.

Canada geese are also able to sleep with only one half of their brain. They can paddle while sleeping, and sleep while flying. This may explain how they’re able to stay on the wing for extended periods of time during their annual migrations.

Research suggests sleep is a phenomenon common to most life forms great, small and microscopic, and stretches back to the early development of life on Earth. How the Wild Things Sleep is a revealing look at one of the great remaining mysteries of the natural world.