A troop of monkeys in Gibraltar has taken up an unusual habit: eating dirt. While this may seem odd, it shines a light on how human habits are affecting wild animals.
Many tourists visit Gibraltar to enjoy breathtaking views and snap photos with the local macaques. Some bring snacks, and the curious monkeys quickly snatch these tasty treats. Over time, these rich foods have become a regular part of their diet, mixing in with their natural fare.
This change isn’t without consequences. The macaques face stomach issues due to foods they aren’t designed to digest. Surprisingly, they’ve started eating soil, a behavior known as geophagy, likely to help their digestive woes.
Dr. Sylvain Lemoine from the University of Cambridge studied these macaques. He explained that the human snacks they consume—high in calories, sugar, and salt—are very different from their usual diet of leaves and seeds. This drastic shift can upset their gut bacteria, leading to discomfort.
In their search for relief, the monkeys turn to soil. Dr. Lemoine’s research suggests that eating dirt may provide minerals and beneficial bacteria. This natural remedy could help soothe gastrointestinal issues. For instance, many non-human primates become lactose intolerant after weaning, making dairy products like ice cream problematic for them.
Interestingly, this isn’t just a random behavior. The monkeys learn from each other. Researchers observed roughly 12 instances of soil eating every week, and nearly 90% of these events occurred when other monkeys were present. This points to a communal learning process.
Location also plays a key role. Monkeys near heavy tourist areas eat more junk food and consequently, more soil. In fact, those close to human activity were two and a half times more likely to snack on human food. Seasonally, as tourist numbers rise, both junk food intake and soil eating increase. When tourism drops in winter, so does their consumption.
Historically, these macaques have coexisted with humans for centuries, likely migrating from North Africa during medieval times. Over the years, they have become a symbol of Gibraltar, even during wartime, when their numbers were carefully maintained.
Despite assistance, like feeding stations providing fruits and vegetables, the allure of junk food remains strong. Dr. Lemoine outlined how humans evolved to crave energy-dense foods as a survival mechanism. This natural instinct may influence the monkeys in a similar way, driving their interest in less nutritious, but more appealing options.
What’s captivating is how quickly animals can adjust to life near people. The macaques not only adapt physically but also develop and share new habits, reminiscent of learned behaviors seen in other primates, like using tools. This blend of biology and cultural learning offers important insights into animal adaptability in human-dominated landscapes.
Gibraltar’s macaques serve as a compelling example of how close contact with humans can shape animal behavior and culture. The full study is available in Scientific Reports.
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