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Wallaby wearable tech probes how light pollution affects sleep

By Alice Klein

7 July 2016

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How well does a wallaby sleep?

Angelo Gandolfi / NaturePL

Don’t nod off. A technology for recording brainwaves in wild animals could awaken a more sophisticated understanding of the function of sleep.

Studies using miniature sleep-recording devices known as neurologgers have already challenged several long-held beliefs about the sleeping habits of sloths and birds.

Three-toed sloths, for example, sleep far less than once thought. And male sandpipers can go almost entirely without sleep during the three-week breeding season, helping maximise their success at that time.

Now, John Lesku of La Trobe University in Melbourne and his colleagues are using neurologgers to investigate whether light pollution interferes with the circadian rhythms of tammar wallabies in Australia.

“The most obvious trait that you might think would respond to human light pollution is sleep, but there’s virtually no data on this,” says Lesku.

Wearable animal tech

To fit the neurologgers, the animals must first be anaesthetised. Fine needles are then used to push tiny hair-like wires underneath the skin, where they rest on the surface of the cranium. These wires transmit EEG brain-activity data to a lightweight wearable tracker the size of a thumbnail.

The neurologgers are well-tolerated by the animals, and can monitor their sleep and identify whether they experience deep slow-wave or rapid-eye-movement sleep.

Light monitors are also fitted to the animals to correlate sleep patterns with night-time light exposure. The technology is currently being tested to make sure it works and get a feel for what wallaby sleep patterns look like in captive populations at La Trobe University, but the next step will be to study the effect of light pollution in the wild.

As part of the project, the researchers plan to study tammar wallabies on an island in Western Australia, which has light pollution on one side and no light other than the stars on the other. A fence divides the two wallaby populations, making it “a nice natural system to see how their sleep differs”, Lesku say.

Clues for human sleep

Studying how animals sleep in the wild can shed light on how and why humans sleep, says Niels Rattenborg of the Max Planck Institute for Ornithology in Seewiesen, Germany.

For instance, in the late 1990s, Rattenborg showed that ducks can sleep with one eye open and one hemisphere of the brain awake if they perceive they are in a risky environment. This finding then inspired a recent study showing that human brains operate in a similar manner when sleeping in an unfamiliar environment.

The traditional reliance on studying sleep in the lab is problematic because animals may alter their sleep patterns in response to captivity, Rattenborg says. “Sleep evolved in the wild, not in the lab. To fully understand its function, we need to study sleep in the real-world context.”

Read more: Sleep: What it is and what it’s for;
Sleep and dreaming: Why can’t we stay awake 24/7?

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