More dominant baboons have less and lower quality sleep

The amount and quality of sleep individuals get can impact various aspects
of human and non-human animal health, ultimately affecting fitness. For
wild animals that sleep in groups, individuals may disturb one another,
influencing sleep quality and quantity, but this aspect of social sleep
has been understudied due to methodological challenges. Here, we test the
hypothesis that individual’s social dominance can affect sleep
opportunities, by studying sleep patterns in a troop of wild chacma
baboons (Papio ursinus), a species with a strong hierarchical social
structure. First, we show that the troop’s night-time sleep (determined by
40Hz acceleration data) is highly synchronised. Next, we link night-time
sleep dynamics to daytime spatial networks and dominance hierarchy (from
1Hz GPS data and direct observations). We show that baboon sleep synchrony
is higher between similarly ranked individuals, and unexpectedly, more
dominant baboons experience less and lower-quality sleep. We propose that
this hierarchy effect is explained by higher-ranked baboons resting closer
to more group members, which also leads them exerting greater influence on
each other’s night-time behaviour compared to lower-ranked individuals.
Our study provides the first empirical evidence for the impact of social
hierarchies on sleep in a wild primate, suggesting that dominance status
may impose trade-offs between social rank and the quality and quantity of
sleep.