Monkeys in a tourism hotspot have learned that swallowing dirt can quell the upset stomachs caused by overconsumption of sweet and salty snacks fed to them by holidaymakers, a new University of Cambridge-led study suggests. Troops of macaques living on Gibraltar—the only free-ranging monkey population in Europe—have been scientifically observed for the first time regularly engaging in geophagy, the practice of intentionally ingesting soil. The work appears in Scientific Reports.