Adolescents are known for risky behavior, with teenagers in the U.S. more likely than younger children to die from injury. But what’s responsible for this uptick in risk-taking around puberty?
Our new observations of physical risk-taking in chimpanzees suggests that the rise in risk-taking in human adolescence isn’t due to a new yen for danger. Rather, a decrease in supervision gives teens more opportunities to take risks.
We study locomotion in chimpanzees, one of humans’ closest relatives. It’s difficult to study physical risk-taking in people because it is not ethical to put anyone in danger. Chimpanzees are good alternative study subjects, since wild chimps of all ages need to move through the trees, often at great heights.
Infant chimpanzees can look determined to try risky moves.
Kevin Lee/Ngogo Chimpanzee Project and Arizona State University
While working with us, Bryce Murray, an undergraduate student at the University of Michigan, noticed that some of the movements that chimpanzees perform in the trees are more dangerous than others.
Typically, chimpanzees climb or swing while keeping a secure grip on branches. However, they also leap across gaps and sometimes let go of a branch entirely, dropping down to another branch or the ground. Unfortunately, they don’t always nail the landing. Years of observations in the wild have shown that falls are a major source of injury and even death among chimpanzees.
After watching these behaviors in chimpanzees, Bryce began to wonder whether their physical risk-taking follows the same patterns we see in humans. Do chimpanzees start taking more risks – like leaping and dropping from branches – once they enter puberty? Since there is evidence that human males take more risks than females, although this varies across cultures, we also wondered whether male chimpanzees are bigger risk-takers than females.
Young chimpanzee daredevils
Our study group consisted of over 100 wild chimpanzees ranging from 2 to 65 years old from Ngogo, Kibale National Park, Uganda.
We found that chimpanzees engaged in their most daring locomotion during later infancy (ages 2-5), with rates of leaping and dropping steadily declining as they aged. Compared with adults (over 15 years), older infants were three times more likely to perform risky behaviors. Juveniles (ages 5-10) were 2.5 times more likely, and adolescents (ages 10-15) were twice as likely. Infants younger than age 2 spend most of their time clinging to their moms, so we didn’t include them in our study.
A young daredevil chimpanzee drops from a branch at Fongoli, Senegal.
Thus, adolescence does not represent a peak in risk-taking for chimps, but rather a point within a gradual age-related decline. Additionally, there were no significant sex differences in risk-taking at any age, consistent with our prior work showing that male…
