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Primates sacrifice sleep to meet life's daily demands

A new study suggests that losing sleep to keep up with the demands of the day is not unique to humans. An international team of scientists has examined sleep behavior among baboons at the Mpala Research Centre in Kenya. The research is the first of its kind to investigate the sleeping habits of a group of primates in the wild.

Study senior author Meg Crofoot is the director of the Department for the Ecology of Animal Societies at the Max Planck Institute of Animal Behavior. She was the first to apply GPS tracking and accelerometry technology to study social behavior in primate societies.

The study revealed that even when the baboons were sleep deprived, they still dedicated time and energy to other priorities – such as socializing or watching out for predators – rather than catching up on lost sleep. 

“We discovered that sleep is a collective behavior in baboon groups. Group-mates were highly coordinated in their patterns of awakening during the night, which in turn led to shorter and more fragmented sleep,” said Crofoot. “Our results show that these highly gregarious animals are balancing their physiological need for sleep with the social pressures of group living.”

Previous studies on animal sleep behavior, which were based on animals in a laboratory setting, revealed patterns of sleep homeostasis. This is a balance in which animals who are sleep deprived will sleep longer or more deeply than usual to compensate for the sleep debt.

The results of the baboon study, however, reveal that animals in the wild face a number of demands that disrupt sleep homeostasis. The baboons were found to sacrifice sleep to stay awake in new environments and to remain close to their group-mates. Regardless of how much they had slept the previous night, or how much energy they had burned up the previous day, the baboons stayed awake and vigilant. 

“The competing priorities that lead humans to accumulate sleep debt might seem unique to a modern, industrialized society like ours. But our findings demonstrate that non-human primates also sacrifice sleep, even when it might be unhealthy to do so, to partake in other activities,” said study lead author Carter Loftus from UC Davis.

“The tradeoff between sleep and other pressing demands on our time is, therefore, one that we have likely been navigating throughout our evolution.”

“Baboons are highly vulnerable to night-time predation and their fitness depends on maintaining strong social bonds. Trading off sleep to maintain alertness in novel, risky environments and to remain close to group-mates during the night may therefore represent an essential adaptation.”

According to Crofoot, the study opens an exciting new frontier of scientific inquiry into the dynamics of sleep.

“The accelerometry-based method can be easily and cheaply integrated into studies tracking animals in their natural habitats, allowing us to massively expand what we know about sleep across a range of species,” explained Crofoot. “In the same way, the technique can be applied to many individuals at the same time, paving the way for understanding how sleeping in groups shapes the structures of animal societies.”

The study is published in the journal eLife.

By Chrissy Sexton, Staff Writer

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