It is not uncommon to see Sumatran orangutans scratching, but now, it appears these primates may be doing more than satisfying an itch. A new study shows loud scratching sounds from Sumatran orangutan mothers serve as a call to their young.
Researchers observed 17 individuals—four mothers and their offspring—in their natural habitat, Gunung Leuser National Park in Aceh in Indonesia. They recorded the behavior of the different mothers and their young before, during, and after the mother made a loud scratching sound by itching the leathery skin on their head, limbs, or body. In most cases the mothers looked at their offspring while scratching, and afterward the two would leave the area together, the team reports today in Biology Letters. After documenting this action nearly 1500 times, the researchers came to believe it was the mother’s way of telling the child it was time to leave.
Female orangutans usually communicate with their offspring through silent gestures to avoid attracting predators. This makes the loud scratching noise even more unusual, the team says. The scientists suggest the orangutans use the scratching sound because it is loud enough and urgent enough to get the child’s attention without being so loud as to alert predators.
The researchers say more studies are needed to fully understand whether orangutans evolved to communicate this way, or whether this signal is specific to just this group of orangutans.