When Orangutan Mothers Scratch Themselves, Youngsters Listen
Animal Stories from All-Creatures.org

FROM Marc Bekoff, Psychology Today/Animal Emotions
August 2019

Orangutan mothers use loud scratches as communicative strategies to coordinate joint travel with their infants.

Orangutan mother child
Source: Sergey Uryadnikov, Shutterstock, Royalty-free stock photo ID: 359830070

An essay in New Scientist by Ruby Prosser Scully titled "Orangutan mothers tell infants where to go by scratching themselves" caught my attention and I'm glad it did. While many behavior patterns that function to communicate different messages to members of the same species can be rather complex, it turns out that recent research shows that orangutan mothers simply noisily scratch themselves apparently to tell their dependent children it's time to move on possibly because there are predators or other orangutans around. The research essay about which Ms. Scully writes by University of Zurich anthropologist Dr. Marlen Fröhlich and her colleagues is called "The loud scratch: a newly identified gesture of Sumatran orangutan mothers in the wild." Ms. Scully's piece is available online, however, only the abstract for the research essay is accessible.

In their abstract, Dr. Fröhlich and her colleagues note that orangutans make self-directed movements such as scratching, however, it's not clear if they use these movements as intentional signals. Using information from studies on wild chimpanzees, they were interested in whether "audio-visual loud scratches are used communicatively in mother–infant travel coordination." More specifically, there wanted to know "whether individual, social and scratch features affected the use of pre-move scratches, markers of intentional signal use and approach responses."

To answer this question, the researchers analyzed 1457 bouts of scratching by 17 wild orangutans living in the Suaq Balimbing forest in Sumatra, including four mothers and dependent youngsters, who were followed for 305 hours. This is a substantial database. Dr. Fröhlich and her colleagues studied what the mothers were doing before and after each scratch, and discovered that loud and exaggerated scratches that could be heard as far as 45 feet away were used to attract the youngsters' attention and alert them that it's time to leave a specific area. When the scratching orangutan was a mother, the youngsters were more attentive to scratching noises then when scratching occurred in other situations. Self-scratching that's used for body maintenance didn't work in the same way. The researchers conclude,"...orangutan mothers use loud scratches as communicative strategies to coordinate joint travel with their infants."

This study clearly shows that simple behavior patterns such as self-scratching can be modified to send a specific signal(s). The major question for which there currently is no answer is whether the noisy self-scratching is an evolved behavior or confined to a local population of orangutans and culturally learned. Dr. Fröhlich notes, "it would not surprise me if they did invent such ‘signals’ from scratch, so to speak, because they are smart, have intentional communication, and can save time and energy by telling their children it is time to go." Future research on other populations of orangutans will help to answer this question.

We will have futurer discussions of the ways in which orangutans and other nonhumans use relatively simple behavior patterns in different contexts to intentionally communicate specific and important messages. It also will be very interesting to learn how they arise and whether they've evolved to serve specific messages or are limited to specific populations and culturally distinct. Who'd have thought a common behavior such as self-directed scratching could take on certain characteristics and tell young orangutans to move on? The simplicity of it all is fascinating.


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