Sleeping elephants: what do their brains tell us about their sleep behaviour — ASN Events

Sleeping elephants: what do their brains tell us about their sleep behaviour (#629)

Paul Manger 1
  1. University of the Witwatersrand, Johannesburg, ACT, South Africa

The current study describes how and when wild African elephants sleep and how clues regarding the control and regulation of sleep have arisen from studies of their brain. Two female African elephants (matriarchs of the herd) were implanted with actiwatches in their trunk and fitted with a collar that measured: (1) their location via GPS, and (2) whether they were standing or lying down, each minute for a period of 6 weeks. Additionally, 10 environmental parameters were measured with a portable weather station. We found that on average, each elephant slept for 2.1 hours per day. Sleep was polyphasic, but the major sleep bout occurred between 3 – 6 am. Interestingly, on nights when the moon was full, the elephants did not sleep, staying awake for up to 48 hours continuously, while on nights of the new moon, the elephants slept for up to 6 hours. While sleep onset time was variable, sleep offset times regularly occurred a few minutes prior to the coldest part of the day. Thus, both light and temperature affect sleep in the wild elephants. The total sleep time is the lowest recorded sleep times of all mammals, presumably to allow the elephants to obtain enough nutrition. Studies of the brain reveal that the arousal system is specialized in two locations, the orexinergic neurons of the hypothalamus and the noradrenergic neurons of the locus coeruleus. Thus, being able to stay awake long enough to obtain enough nutrition, is correlated with specializations of two parts of the neuronal arousal systems.