Monkeys in Gibraltar have learned to eat soil to settle their stomaches from all the junk food they consume. Scientists believe the dirt helps the monkeys line their guts to stop irritation from the foods, which are extremely high in calories, sugar, salt and dairy. The soil also provides bacteria and minerals missing from junk food offered by or stolen from tourists, such as chocolate bars, chips and ice cream. The snacks have negative digestive effects for the macaques and can cause symptoms from nausea to diarrhea, even though the food is delicious to them. Animals in frequent contact with Gibraltar’s visitors were observed to eat more dirt, with this behavior being higher during peak holiday season. The researchers think the behavior is likely to have been learned socially as different troops of monkeys have preferences for certain types of soil. Experts said the soil acts as a "barrier" in the digestive tract and limits the absorption of harmful compounds. Humans evolved to seek out and store energy-dense fats and sugars to survive periods of scarcity, leading us to crave high-calorie junk food, and the availability of junk food could trigger this same evolutionary mechanism in the monkeys. Gibraltar’s macaques number around 230 across 8 groups that inhabit different areas of the Rock. Scientists recorded 46 dirt-eating "events" in 44 different animals across 98 observation days.
