Elephants in their natural environment sleep an average of only two hours a day, according to recent research conducted by Professor Paul Manger of the School of Anatomical Sciences at Wits University.
“Sleep is one of those life-sustaining things we all have to have. While there are many hypotheses regarding the function of sleep, the ultimate purpose of sleep is yet to be discovered,” said Manger
He explained that the lack of sleep can, even over a relatively short term lead to brain damage, and in the longer term death, as can be seen in the human conditions of fatal familial insomnia and sporadic fatal insomnia.
All animals do sleep and some, like whales, dolphins, seals and certain birds, do it in a very unusual manner, sleeping with only half their brain at a time, while some sleep quite a lot and others less so.
Generally, larger animals tend to sleep less than smaller mammals. Behavioural studies of elephant sleep in zoos record that they sleep around four hours a day and can sleep standing up or lying down.
Manger, together with Dr Nadine Gravett and Dr Adhil Bhagwandin, also from the university’s School of Anatomical Sciences, along with colleagues from the non-governmental organisation Elephants Without Borders in Botswana and the University of California, worked on this research in the Chobe National Park in Botswana.
The team made use of small activity data loggers, scientific versions of the well-known activity tracker Fitbit, to study the sleeping patterns of elephants in the wild.
HI-TECH TOYS: A matriarch elephant wears a GPS collar fitted with a gyroscope and a data logger in her trunk to assist scientists with their research in the wild.
“We reasoned that measuring the activity of the trunk, the most mobile and active appendage of the elephant would be crucial, making the reasonable assumption that if the trunk is still for five minutes or more, the elephant is likely to be asleep,” said Manger.
The team implanted two matriarch elephants with the data logger under the skin of their trunk, noting when the large mammal did and didn’t use their trunk and when they moved around.
A GPS collar was also fitted with a gyroscope around their necks to monitor where and when the elephants were lying down to sleep.
The main finding of the study, recently published in the journal PLOS ONE, was that the two matriarch elephants slept only two hours a day on average, and this sleep occurred mostly in the early hours, well before dawn.
“The data also indicates that environmental conditions like temperature and humidity, but not sunlight, are related to when the elephants fell asleep and when they woke up, which happens well before dawn,” Manger said.
“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,” he said.
They also noted that the wild elephants could sleep while standing up or lying down. It was found that lying down to sleep only happened every three or four days for about an hour.
Manger explained that it’s likely that the only times they go into rapid eye movement (REM) sleep, (which is the type of sleep where mammals dream), was when they were lying down.
“This means elephants possibly don’t dream on a daily basis like we do, but may dream only every few days.
“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,” said Manger.
Finally, the team found that the two elephants, when disturbed by such things as predators, poachers, or a bull elephant in musth, could go without sleep for up to 48 hours.
“Following the disturbance, the elephants would walk up to 30km from where the disturbance occurred. This puts a great deal of distance between the elephant herd and any source of danger, but at the expense of a loss of a night’s sleep,” he explained.
Manger said there were two reasons why it was important to understand how different animals sleep.
“First, it helps us to understand the animals themselves and discover new information that may aid the development of better management and conservation strategies.
“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,” he concluded.
Along with activities such as eating, protecting oneself and reproducing, sleep is one of the major biological imperatives of existence.
@Lanc_02