Sleeping with the enemy: elephants alter rest behavior in risky areas
Submitted by editor on 18 April 2017.
By Laura Keating and George Wittemyer
Sleep has been hypothesized to be fundamental to cognitive functioning, and extreme sleep deprivation can have lethal implications. In addition, sleep is one of the most susceptible times of day for an animal. Given its fundamental importance, the selection of sleep locations by animals is critical to their survival and likely indicative of the landscape features they value or fear.
Despite being one of the most cognitively advanced species on the planet, African elephants sleep less than just about any other mammal (Gravett et al. 2017). Their ability to function at a high level, coupled with their long lifespans, has upended many hypotheses about the importance of sleep to animal brains. We interpret these findings as indicators of the importance of the relatively rare sleep events by elephants and set out to investigate sleep patterns in wild elephants to gain greater understanding of habitat-behavior interactions in this species.
In a recent paper published in Ecography, we examined the pattern and locational properties of sleep locations use by wild African elephants in northern Kenya. We used graph (network) theory to investigate the spatial and temporal features that structure elephant rest locations, in one of the first applications of these methods to continuous tracking data. Our results suggest that elephants adjust resting behavior in relation to important landscape features, the most important of which was the presence of humans. Elephants altered when and where they sleep when in human-dominated areas, presumably to reduce the risk of interactions with humans, their primary predators.
In addition to providing insight into the secret world of elephant sleep, our results also show that graph theory is a powerful framework for investigating behaviors that are discrete in time and space (e.g. resting). We hope that this research inspires future graph-theoretic investigations of spatially and temporally discrete behaviors in other species and systems.
References
Gravett, N., Bhagwandin, A., Sutcliffe, R., Landen, K., Chase, M.J., Lyamin, O.I., et al. 2017. Inactivity/sleep in two wild free-roaming African elephant matriarchs – Does large body size make elephants the shortest mammalian sleepers? - PLoS ONE 12: e0171903. doi:10.1371/journal.pone.0171903