Wild baboons sacrifice sleep to meet pressing demands

Date:
March 1, 2022
Source:
Max-Planck-Gesellschaft
Summary:
Sleep study on a troop of wild baboons reveals that sacrificing
sleep to meet pressing demands is common -- and might even be part
of our evolutionary history.



FULL STORY ==========================================================================
The first study ever to examine sleeping behavior in a wild group of
primates has challenged a central tenet of sleep science: that we must
make up for lost sleep. Even after sleeping poorly, wild baboons still
spent time on other priorities, such as socializing with group-mates or
looking out for predators, rather than catching up on lost sleep. The team
of scientists from the Max Planck Institute of Animal Behavior and the University of California, Davis used non-invasive technology to monitor
sleep patterns across almost an entire group of individuals at once. The findings lay bare the competing priorities that suppress sleep homeostasis
in wild primate societies -- raising the possibility that humans have
navigated sleep deprivation throughout our evolutionary history.


========================================================================== Studies of sleep have revealed that animals of every species, from honey
bees to humans, put aside a portion of each day to rest. But, with some
notable exceptions, all sleep studies share the same thing in common:
they were conducted on animals in the laboratory. In laboratory settings, animals perform the phenomenon known as sleep homeostasis -- an animal
with an accumulated sleep debt will later sleep longer or more deeply
than usual. Sleep homeostasis has long been considered a key criterion
in the very definition of sleep.

But the new study published in eLife demonstrates that animals in the
wild face a slew of ecological and social demands that can disrupt
sleep homeostasis.

Specifically, baboons sacrificed sleep to stay awake in new environments
and to remain close to their group-mates, regardless of how much they
had slept the prior night or how much they had exerted themselves the
preceding day.

The study was led by PhD student Carter Loftus from the University of California, Davis. He said: "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. 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." To identify when animals
were sleeping and when they were awake, the team collected high resolution movement data from GPS trackers and accelerometers attached to almost all baboons in a troop. As the first study to investigate collective sleeping behavior in wild primates, the findings bring to light the unknown social
costs and benefits associated with sleep in animal societies.

Baboons experienced shorter, more fragmented sleep when sleeping near
more of their group-mates. However, they also synchronized periods of
nocturnal awakening with nearby individuals, suggesting that baboons may
have actually been interacting with each other and strengthening their
social bonds over night.

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

"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. Our results show that these highly gregarious
animals are balancing their physiological need for sleep with the social pressures of group living." Working at the at the Mpala Research Centre
in Kenya, the team fitted 26 wild baboons with GPS and accelerometry
collars. In contrast to well-established methods used in sleep studies,
which typically involve surgically implanting electrodes to measure
brain activity via electroencephalography, the technique used in the
present study represents a non-invasive alternative that can identify
periods of sleep and wakefulness in wild, free ranging animals. The GPS trackers provided information on where the animals moved. This enabled
the researchers to answer questions such as: how far the animals had
traveled during the day, in which sleep site they slept, and with
whom they slept. The accelerometers, which are similar to smartwatch
and Fitbit technology, gave ultra high-resolution information on body movements. By applying an algorithm adapted from studies of human sleep,
the researchers used accelerometry data to determine when the baboons were asleep or when they were awake. They then used thermal video recordings
of sleeping baboons to validate their findings.

"This study opens an exciting new frontier of scientific inquiry into
the dynamics of sleep," adds Crofoot. "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. 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." ========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. J Carter Loftus, Roi Harel, Chase L Nu'n~ez, Margaret C Crofoot.

Ecological and social pressures interfere with homeostatic sleep
regulation in the wild. eLife, 2022; 11 DOI: 10.7554/eLife.73695 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220301131112.htm

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