Chimpanzees build their beds and they are good at it

August 9, 2019

Chimpanzees choose the branches of certain trees that provide them with the safest and most stable place to sleep, says a 2014 study.

Furthermore, the research supports the theory that good quality sleep contributed to the evolution of modern humans, said the study leader, David Samson , anthropologist at the University of Nevada, Las Vegas.

Chimpanzees build their beds - called nests - in the crowns of trees using the branches of certain tree species. They spend about eight to nine hours a night on these plant platforms.

The study was published April 16, 2014 in the journal PLOS ONE . Until this study, scientists did not know how chimpanzees select building materials.

Samson and his colleagues compared the bending stiffness and flexibility of seven tree species most commonly used by chimpanzees in Toro-Semliki Wildlife Reserve from western Uganda. The team also analyzed the surface area of ​​the leaves on the trees and the structure of each tree species. What they found was remarkable: of the 1,844 chimpanzee nests studied, 73.6% were built from a sturdy tree called the Ugandan ironwood - even though that species only makes up 9.6% of the trees the region. "Despite the fact that the iron tree is relatively rare, the chimpanzee seems to say, seven times out of ten, 'I want to sleep in this tree,'" Samson said.

A sturdy wood

Chimpanzees in the Toro-Semliki Wildlife Sanctuary sleep in trees primarily to avoid nocturnal predators such as leopards or lions. For this reason, their beds must be very durable, without any risk of the chimpanzees falling during the night. Ironwood was the top choice of the seven tree species tested in the study, so "it's probably the best bed-building material," Samson said.
The branches of the iron tree also have a certain distance between the shoots, this makes them easy to weave together, which chimpanzees do to make sure their bed is strong.
The branches of the iron tree allow for "a more robust locking system similar to springs tied in a mattress," says the researcher. "They are as anxious at night about a comfortable sleep as you or I." Chimpanzees know that ironwood is "a special species of tree - they can recognize these properties," he said.

Aaron Sandel, an anthropo-biologist at the University of Michigan in Ann Arbor, who was not involved in the study, said there are not enough studies on chimpanzee sleep but that this new research is a "cool idea". He, however, agreed with the results that "chimpanzees generally choose trees based on safety and ease of nesting."

But what about chimpanzees in other parts of Africa? Study author David Samson said there is evidence that other populations also choose the wood that provides the best sleep, depending on the environment and the tree species available in their area.

Did sleep make us smart?

Finally, David Samson wants to know if sleep played a role in human evolution. For example, large primates (including us) are unique in that they build nesting platforms or even beds. Other primates sleep directly on branches. Sometime during the Miocene, 23 – 25 million years ago, ancient apes changed their sleeping locations from bare branches to built platforms. This change led to better sleep.

Studies in both humans and orangutans show that better quality sleep, with longer periods of rapid eye movement, improves cognition and memory. Better sleep in old monkeys appears to have led to improved cognition the day after a night in cozy beds. But it's also possible that apes' large brains led to the need for more sleep, not the other way around, Sandel noted.

"In any case," said Samson, "an additional boost in cognition certainly gave apes and humans an evolutionary advantage."

"Big brains", said David Samson, "need big pillows".

Source: https://www.nationalgeographic.com/news/2014/4/140416-chimpanzees-trees-sleep-beds-animals-science/