Novel investigation of western lowland gorilla sleep architecture.

Abstract

Sleep behaviour has been recorded for only ten percent of primate species. Here, we contribute to this literature by using videography to collect novel sleep behaviour data on captive gorillas. We measured, to our knowledge, the first ever sleep architecture preliminary baseline estimate data in a population of captive western lowland gorillas (Gorilla gorilla gorilla) at the Basel Zoo (Switzerland) over three months (n = 90 nights of observation). The results of this study showed significant differences in levels of sleep fragmentation between the one dominant male of our gorilla community and the subordinate individuals (one young male and females ranging in age) of the same community. This perhaps suggests that dominant individuals may suffer in their overall sleep quality however, because dominance and sex are confounded in this population, these patterns should be interpreted cautiously. While this result could be interpreted to be tradeoff between the requirements of sleep and group protection by the dominant silver back, the results of this study are novel and the first of its kind. Thus, while these preliminary differences raise questions about how social roles may relate to sleep behaviour in gorillas, further research with larger samples is required to understand how biological sex, dominance rank, and the interaction between the two within gorilla populations, influences sleep within gorillas.