Gibraltar's Monkeys Learn to Eat Dirt After Tourist Snacks

When your stomach hurts from too many treats, you might reach for medicine. Gibraltar's famous monkeys have found their own solution: dirt.

About 230 Barbary macaques living on the Rock of Gibraltar have learned to eat soil to soothe digestive problems caused by tourist snacks. They're munching on ice cream, cookies, and bread handed out by visitors, despite signs asking people not to feed them.

Researchers from the University of Cambridge watched the monkeys for nearly 100 days between August 2022 and April 2024. They spotted 44 different macaques eating dirt a total of 46 times, often right after snacking on human food.

The connection was clear. Monkeys near the top of the Rock, where tourists gather most, ate the most junk food and the most dirt. Meanwhile, a group that avoided tourists was never seen eating soil at all.

When winter arrived and tourist numbers dropped, the macaques were 40 percent less likely to eat human food and 31 percent less likely to eat dirt. The seasonal pattern confirmed what scientists suspected.

"We think the macaques started eating soil to buffer their digestive system against the high-energy, low-fiber nature of these snacks and junk foods," says study co-author Sylvain Lemoine. The dirt acts like a protective barrier in their stomachs, blocking harmful compounds and easing symptoms from nausea to diarrhea.

Local authorities feed the monkeys fruits and vegetables every day, but the animals still prefer stealing tourist treats. Tour guides sometimes encourage feeding, even though it's against the rules.

These Barbary macaques are the only wild monkeys in Europe and the only macaque species living outside Asia. They've divided into eight stable groups across Gibraltar's famous mountain.

The Bright Side

This isn't just a quirky monkey story. It reveals how incredibly adaptable wildlife can be when faced with human changes to their environment. The macaques invented their own antacid solution without any instruction.

Scientists have seen similar behavior at Japan's Arashiyama Monkey Park, suggesting this might be an emerging survival strategy for primates living near humans. It's a reminder that nature finds ways to cope, even in less-than-ideal circumstances.

Still, experts say the better solution is obvious: stop feeding the monkeys junk food. While their dirt-eating trick shows remarkable intelligence, preventing the problem beats treating the symptoms.

These clever primates are teaching us something important about resilience in a changing world.