He recognized its suitability for that purpose
In the forests of Uganda, where human settlement and wild habitat increasingly overlap, a young chimpanzee named Araali did something no wild ape had been recorded doing before — he repurposed a discarded plastic bottle, a relic of human agriculture, for his own sexual gratification. Documented by researchers in 2018 and published in 2021, the observation is less a curiosity than a quiet testament to the adaptability of minds shaped by proximity to our own. It raises old questions anew: where does instinct end and improvisation begin, and what does it mean when another species begins to inhabit the world we have made?
- A subadult chimp in Bulindi, Uganda was filmed using a discarded herbicide bottle for a 25-second sexual act — the first documented case of a wild ape using a man-made object this way.
- The chimp's relaxed 'play face' throughout the encounter suggested genuine pleasure, not distress, complicating simple assumptions about animal behaviour and sexual function.
- When Araali lost interest and walked away, troop members briefly picked up the bottle themselves — hinting at the social ripple effects of novel object encounters in the wild.
- Researchers from three universities published their findings with admitted disbelief, noting the behaviour reflects how deeply human encroachment is reshaping wild ape behavioural repertoires.
- The case now sits at the centre of broader scientific questions about masturbation's function in male chimpanzees and how manufactured objects alter the behavioural landscape of wild animals.
In 2018, scientists monitoring a small chimpanzee community in Bulindi, Uganda, filmed something unprecedented: a young male named Araali using a discarded plastic herbicide bottle — almost certainly abandoned by a nearby farmer — for sexual self-stimulation. He placed the bottle on the ground and engaged in sustained pelvic thrusting for twenty-five seconds, wearing what primatologists call a "play face," a relaxed open-mouthed expression associated with enjoyment rather than distress.
At one point Araali lost his grip on the bottle, calmly repositioned himself, and continued. He eventually disengaged without reaching climax and wandered off. Other members of the troop briefly investigated the bottle before losing interest themselves.
Researchers Matthew McLennan and Kim van Dijk, affiliated with Oxford Brookes, Exeter, and Utrecht universities, published their account of the encounter this month. Their analysis points to Araali's unusual familiarity with human-made objects as the key factor — living on the edge of human settlement, he has encountered manufactured items far more than most wild apes, and apparently learned to assess their utility in ways his more isolated counterparts would not. The bottle's shape and smooth interior, they suggest, triggered a recognised sexual response.
Masturbation itself is not rare among wild chimpanzees, who have been observed using natural objects for the same purpose. What is new here is the manufactured origin of the object — a product of human industry, discarded into a wild habitat, and repurposed by its accidental inheritor. The researchers note that as human settlements expand further into ape territory, such encounters will only grow more frequent, and Araali's case offers an early window into how behaviourally flexible wild apes can be when the human world encroaches on their own.
In 2018, researchers monitoring a troop of nineteen chimpanzees in Bulindi, Uganda, witnessed something no scientist had documented before in a wild ape: a male chimp using a discarded plastic bottle as a sexual object. The chimp, a subadult male named Araali, positioned the bottle—a container that had once held herbicide, likely abandoned by a farmer—flat on the ground in front of him and engaged in sustained pelvic thrusting for twenty-five seconds. Throughout the act, he displayed what researchers call a "play face," a relaxed open-mouth expression that suggested not distress but pleasure.
Matthew McLennan and Kim van Dijk, scientists from Oxford Brookes University, the University of Exeter, and Utrecht University, documented the encounter in detail. At one point during the encounter, Araali's genitals slipped out of the bottle's opening. He repositioned himself and reinserted, then sat with the play face intact for the remaining eight seconds of the recording, apparently still engaged with the object. When he eventually lost interest and moved away—without reaching climax, the researchers noted—other members of the troop picked up the bottle and played with it briefly before discarding it themselves.
The significance of the observation lies not in the act itself but in what made it possible. Masturbation among wild chimpanzees is not uncommon; researchers have previously observed males pleasuring themselves by manipulating their own bodies or using natural objects like smooth stones or fruit. What sets Araali's behavior apart is the use of a manufactured item—something created by humans and discarded in his habitat. The researchers believe this choice reflects Araali's unique position: living in close proximity to human settlements, he has become familiar with man-made objects in ways that most wild apes never are. Where another chimp might ignore or avoid such an item, Araali recognized its potential utility.
The paper McLennan and van Dijk published this month drew considerable attention, with the researchers themselves noting on social media that "this is a paper I never thought we'd write." Their analysis suggests that the bottle's physical properties—its open end, its smooth interior surface—triggered Araali's sexual response. He appeared to recognize, consciously or instinctively, that the object suited his purpose. The play face he maintained throughout indicated that the experience was not merely functional but genuinely enjoyable, suggesting that masturbation in male chimpanzees may serve a pleasure-seeking function beyond simple sexual release.
The observation opens broader questions about how wild apes respond to novel objects introduced into their environment through human activity. As human settlements expand and wild habitats become increasingly interspersed with human infrastructure, apes encounter manufactured items with growing frequency. Araali's case demonstrates that some individuals don't simply tolerate these objects—they integrate them into their behavioral repertoire in unexpected ways. The researchers note that this unusual finding contributes to a deeper understanding of the behavioral flexibility wild apes display when confronted with the material world humans have created around them.
Citas Notables
This is a paper I never thought we'd write— Researchers Matthew McLennan and Kim van Dijk, posting on social media
The physical properties of the open bottle presumably elicited Araali's autoerotic response, suggesting he recognised its suitability for that purpose— The research paper's analysis of Araali's behavior
La Conversación del Hearth Otra perspectiva de la historia
Why does it matter that this chimp used a plastic bottle rather than, say, a stone or a piece of fruit?
Because it tells us something about how wild animals adapt when humans move into their world. A stone is part of the chimp's natural environment. A bottle is not. The fact that Araali recognized its potential suggests he's learned to see human objects not as foreign intrusions but as tools he can use.
Do you think he understood what he was doing, or was it just accident?
The researchers think he recognized the bottle's suitability. He positioned it deliberately, repositioned when needed, and showed signs of pleasure the whole time. That's not random fumbling. Whether that constitutes "understanding" in the way we'd use the word—that's harder to say.
The paper mentions he lives near humans. Does that change how we should think about his behavior?
It changes everything, really. Araali isn't isolated in some pristine forest. He's in a landscape shaped by human activity, surrounded by human objects. In that context, his behavior isn't aberrant—it's adaptive. He's using what's available to him.
What happens now? Will other chimps start doing this?
That's the open question. It depends on whether other chimps in his troop learn from him, and whether they have the same familiarity with human objects. Behavior can spread through populations, but only if the conditions are right.
Does this tell us anything about wild ape intelligence?
It suggests they're more flexible, more capable of innovation, than we sometimes give them credit for. They don't just use objects the way their ancestors did. They adapt. They experiment. They find new uses for new things.