How do you measure the sleep of a mammal weighing several tonnes, that could flatten you in seconds? Tranquilise it and tuck a fitness tracker in its trunk. This was the approach used by a team from the School of Anatomical Sciences at the University of the Witwatersrand, South Africa, to understand the true nature of the wild African elephant's sleep pattern.
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Measuring sleep in a controlled area, such as a lab or zoo, where the animals can be monitored at all times, is straightforward. However, their behaviour is unlikely to reflect natural habits due to the lack of predators and artificial abundance of food sources.
According to current knowledge, elephants sleep around four to six hours a day in zoos, but professor Paul Manger, who headed up this latest research and has been studying animal sleep for almost 20 years, knew this was not an accurate representation.
Together with teams from Elephants Without Borders, Botswana, and the University of California, Manger and his Witwatersrand colleagues used a science-grade version of a Fitbit to record the elephant’s sleep duration and position. The trunk was chosen because it is the most “active appendage of the elephant”, Manger explained. The device recorded any pause in motion of five minutes or more. This pause was interpreted as sleep, and a gyroscope attached to the elephants’ necks told researchers whether the animals were lying down or standing.
Over a period of five weeks, the elephants, both females and matriarchs of their herd at Chobe National Park, slept only a couple hours a day.
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They often slept in a standing position, and only lay down to sleep every three to four days. The team speculates that these were the only occasions the elephants went into REM sleep, meaning they dreamt infrequently. If needed, when predators were close by, they could stay awake for two days straight.
When they did sleep, it usually took place before dawn, suggesting it was linked to the local temperature and humidity and not sunlight. "This finding is the first that indicates that sleep in wild animals is likely not to be related to sunrise and sunset, but that other environmental factors are more crucial to the timing of sleep," Manger said. The fact the elephants may only go into REM every few days, has potential implications for our understanding of the relationship between sleep and memory, he continues: "REM sleep (or dreaming) is thought to be important for consolidating memories, but our findings are not consistent with this hypothesis of the function of REM sleep, as the elephant has well-documented long-term memories, but does not need REM sleep every day to form these memories."
"Understanding how different animals sleep is important for two reasons. First, it helps us to understand the animals themselves and discover new information that may aid the development of better management and conservation strategies, and, second, knowing how different animals sleep and why they do so in their own particular way, helps us to understand how humans sleep, why we do, and how we might get a better night's sleep."
The study was published in PLOS One.
This article was originally published by WIRED UK
