A surprising side effect of monkey grooming

Peter Henzi

A surprising side effect of monkey grooming

It’s a familiar image: a group of monkeys assembled in a line, picking carefully through each other’s hair, eating any treasures they might find. The grooming ritual so common in many primate species serves to both keep the monkeys healthy as well as reinforce social structures and bonds. But according to new research on vervet monkeys (Chlorocebus pygerythrus, seen above), the behavior may also improve a pelt’s insulation by fluffing it up like a duvet, scientists report in the American Journal of Primatology. To test the difference between groomed or ungroomed fur, the team manually combed vervet monkey pelts either with or against the grain for 50 strokes. The fluffed up “backcombed” pelts simulated a recently groomed monkey, whereas the flattened pelts simulated an ungroomed state. Using a spectrophotometer, the researchers then measured how much light was reflected by each pelt and calculated the pelt’s total insulation. They found that a thicker, fluffier coat could improve a monkey’s insulation by up to 50%, keeping the animal warmer in the cold and cooler in the heat. Thus, grooming may help the vervets maintain a constant body temperature with less effort, freeing up more energy for sex, foraging, and participating in monkey society. In the face of climate change, the authors note, such flexibility could soon become enormously important. 

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