Chimpanzees (Pan troglodytes) select a certain type of wood to make their nests, says a team of biologists from the United States.
A male chimpanzee at the Toro-Semliki Wildlife Reserve, Uganda. Image credit: © Caroline Deimel, 2012
Daily construction of a nest is a universal behavior among large-bodied hominoids. Among chimpanzees, most populations select certain tree species to sleep in more frequently than other, but the reason for selecting a particular tree is unclear.
To determine whether the physical properties of trees influenced nesting site selection, Dr David Samson from the University of Nevada and Dr Kevin Hunt from Indiana University measured the physical characteristics of wood from common tree species at the Toro-Semliki Wildlife Reserve, Uganda.
They measured the stiffness and bending strength of 326 branches from the seven tree species most commonly used by the chimps. Additionally, they measured leaf surface area and determined the structure or architecture of each of the seven species.
Of 1,844 nests sampled, chimpanzees selected Ugandan ironwood (Cynometra alexandri) for 73.6 percent of the nests, even though it represented only 9.6 percent of all trees in the sample area.
Ugandan ironwood, also known as Muhimbi, was the stiffest and had the greatest bending strength of all the trees tested, had the smallest distance between leaves on the branches, and had the smallest leaf surface area.
Dr Samson and Dr Hunt suggest that chimpanzees select trees, like the Ugandan ironwood, due to these properties, as they may provide protection from predators and pathogens, as well as provide temperature regulation and comfort.
“Chimpanzees, like humans, are highly selective when it comes to where they sleep. This suggests that for apes there is something inherently attractive about a comfortable bed – down to what kind of wood you use to make it,” explained Dr Samson, the first author of the paper published in the journal PLoS ONE.
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Samson DR, Hunt KD. 2014. Chimpanzees Preferentially Select Sleeping Platform Construction Tree Species with Biomechanical Properties that Yield Stable, Firm, but Compliant Nests. PLoS ONE 9 (4): e95361; doi: 10.1371/journal.pone.0095361
