In a fascinating look at animal sleep and social behaviour, a new study reveals how sleeping together bonds animals, just as it does humans.
Researchers found animals that slept together exhibited increased attraction and moved in cohesive formations for up to three days after co-sleeping.
They tracked wild olive baboons in Mpala Research Centre in Laikipia, observing how sharing sleeping sites affected intergroup dynamics and sleep quality.
They tranquilised and fitted the animals with GPS and accelerometers then monitored six adult female baboons from four social groups, recording data over a year.
The findings are published in the Proceedings of the Royal Society B journal. They open new insights into the complex interplay between sleep and social behavior in animal groups.
“Our study shows night-time co-sleeping can have remarkable effects on the way these animals behave together during the day,” the authors said in their study, titled “Sharing sleeping sites disrupts sleep but catalyses social tolerance and coordination between groups”.
The baboons that shared sleeping sites showed a clear pattern of spatial attraction to the groups they co-slept with.
“Sharing sleeping sites seems to create a temporary bond between the groups, even in species like olive baboons, which usually have more competitive relationships,” they said.
On the days following shared nights, the chances of groups moving cohesively increased nearly five-fold, indicating social interactions established during the night carried over into daytime behaviours.
“Baboon groups behaved differently during these interactions as compared to those that took place when groups had not slept together on the preceding night: interactions were, on average, nearly twice as long and groups were more than four times as likely to travel cohesively,” the authors said.
This study says sleep can have a significant social component, affecting intergroup relations in a way that traditional studies of animal behaviour may have missed.
“To satisfy their need for sleep, all animals must make decisions about when, where and with whom they can safely enter this vulnerable state. These choices are consequential, yet behavioural research focuses almost exclusively on what animals do during their waking periods and researchers have largely ignored animals’ sleep periods and the potential consequences of their night-time decisions,” the report says.
Another significant finding is that sharing sleeping sites disrupted sleep for baboons. Data showed baboons sleeping with other groups experienced shorter, more fragmented sleep, with a 33-minute reduction in total sleep time and a 1.2 per cent decrease in sleep efficiency on shared-site nights.
Furthermore, these baboons experienced about additional awakenings per hour, indicating that intergroup sleep may come at a considerable cost.
The co-sleeping baboons exhibited synchronised wake-sleep patterns, often rousing simultaneously in response to disturbances during the night.
“This synchronicity goes against the ‘sentinel hypothesis,’ which posits that co-sleeping animals should alternate their wake periods for vigilance,” indicated Lead author Carter Loftus.
By suggesting the quality of sleep — and
the social interactions that occur during these vulnerable periods, the study sheds light on how animals make
complex trade-offs to balance survival.
