Arboreal primates spend much of their lives grappling with trees. But Verreaux’s sifakas might be the only ones to spend hours at a time sitting on the ground with their arms wrapped around a tree trunk and their bellies pressed up against it.
“When we saw the animals doing it, we were totally amazed,” says Yale University’s Chloe Chen-Kraus, lead author of a new report published in the International Journal of Primatology that investigates the function of the bizarre behaviour. “Our local guides had seen it before, but it hadn’t been described in the scientific literature.”
During her study in Madagascar’s Bezà Mahafaly Special Reserve, Chen-Kraus and her colleagues found evidence that hugging trees helps the lemurs to cool down in hot conditions.
The behaviour occurred only when the ambient temperature exceeded 30°C, when the trunks of the hugged trees were three to five degrees cooler than the surrounding air and the higher branches.
“These trees are sucking cool water from deep in the ground, which is warmed by the surroundings as it rises up the trunk,” says Chen-Kraus. “So, if the animals are willing to take the risk of coming all the way down, that gives them the greatest thermal advantage.”
The risk is that sifakas are most vulnerable to predators at ground level. “Domestic dogs are a big problem. The lemurs get really scared if they hear a dog barking, even if it’s far off in the distance,” says Chen-Kraus. “They’re just more comfortable up in the trees if they’re feeling threatened.”
Main image: Tree hugging Verreaux's sifaka lemurs. © Chloe Chen-Kraus