Chimpanzees at the Chimfunshi Wildlife Orphanage Trust in Zambia have been observed displaying a peculiar behavior: wearing blades of grass in their ears and rears. It was researchers who initially spotted this fascinating trend back in 2010. Since then, its allegations have created a firestorm of interest amongst scientists studying animal behavior and culture practice.
And it all began with one matriarchal female chimpanzee. She kept jabbing a piece of grass into her ear and I felt like she had little real world reason for doing so. Her behavior created a ripple effect within the organization, causing seven other chimpanzees to join her in her new routine. This regressive trend has proven to be surprisingly stubborn. Even in the years since the original trendsetter’s passing, many members of the culture continue to fully adopt this behavior to this day.
Utrecht University’s Rebecca Clements and Durham University’s Eric W. B. C. Wigley, along with other researchers, have investigated this cascading behavior. They see it instead as a cultural tradition among chimpanzees. Together these observations suggest that this freakish practice could fulfill social functions within the group’s hierarchy.
A Trendsetter Among Chimpanzees
In 2010, researcher Edwin van Leeuwen conducted a preliminary observation of this behavior. What he hadn’t planned to do was to document the secretive behavior of a female chimpanzee at the sanctuary. This lady doubled as a trailblazer, encouraging other members of her flock to take up the same strange behavior.
For both the groups where chimps inserted grass blades in their ears,” Van Leeuwen pointed out, “the same caretakers. To clean ears, these caretakers said they would occasionally stick a piece of grass or matchstick in their own ears. Perhaps most interesting, caregiver behaviors could affect chimpanzees’ actions. This begs further interesting questions about the origins and motivations behind these seemingly mundane practices.
In a different experiment, researchers found that five of eight chimpanzees in an unfamiliar group engaged in this behavior. Instead of doing that, they shoved grass into their ears! Furthermore, a whopping six out of eight chimpanzees in the same social group allowed strips of grass to hang from their backsides. This behavior is clearly not a one-off. It has become an inclusive, movement-building activity that’s taken on a life of its own among diverse—and often unexpected—groups.
Copied Behaviors and Social Bonds
Taking grass blades on the head looks very much like a learned behavior, not preordained instinct. Chimpanzees imitate each other’s actions—often in ways that serve no clear purpose—showcasing their impressive ability to learn from others. “Our study shows that chimpanzees are able to copy small, useless behaviors from each other,” said Jake Brooker, a researcher involved in the study.
Van Leeuwen noted that the focus shouldn’t just be on whether or not chimpanzees do this, but rather on why they do it. “Why they do exactly this particular thing, I’m not really concerned about,” he stated. “But them copying the behavior from each other, that is the important insight.” This empirical understanding provides an important window into how chimpanzees experience some social dynamics more commonly seen in humans, namely how behaviors can be adopted through imitation.
The social component to this behavior is notable though. According to Van Leeuwen, “It could also serve a social purpose. By copying someone else’s behavior, you show that you notice and maybe even like that individual.” This mimicry can serve to reinforce social ties and create a feeling of group inclusion, reflecting similar processes in people.
Cultural Implications and Future Research
The ongoing observations at the Chimfunshi Wildlife Orphanage Trust provide valuable insights into the cultural traditions of chimpanzees and their ability to replicate behaviors without apparent utility. As researchers further study these behaviors, they learn more about animal culture and what it means about the nature of culture, which has deep implications for human evolution.
“This shows that like humans, other animals copy seemingly pointless behaviors from one another,” Edwin van Leeuwen remarked. He added that such findings may offer insights into “the evolutionary roots of human culture.”
The grass-wearing fad among chimpanzees at the sanctuary continues. This leads to interesting questions about the processes by which cultural practices evolve between groups of individuals. It hints at the complex social landscape that many animals other than humans traverse. As technology advances, this highlights the importance and need for research to more thoroughly understand these new behaviors.