Monkeys discover unusual tactic that lets them binge on junk food – don’t try this at home | UK | News
Gibraltar’s famous Barbary macaques have come up with a clever but dirty solution to the dangers posed by tourist aid: They swallow soil to calm their stomachs after gorging on chocolate, chips, ice cream and other junk food. A study from the University of Cambridge has documented, for the first time, regular “geophagy” (deliberate eating of dung) among Europe’s only free-ranging monkey population. Troops in closest contact with holidaymakers are eating much more land, with rates rising rapidly during the busy summer season.
Researchers believe that high-sugar, high-fat, low-fiber snacks disrupt the monkeys’ gut microbiome and cause digestive problems. Eating dirt appears to act as a natural buffer lining the intestines, providing minerals and beneficial bacteria and limiting the absorption of irritating compounds.
Cambridge biological anthropologist Dr. Sylvain Lemoine explained: “The food brought by tourists and eaten by Gibraltar macaques is extremely rich in calories, sugar, salt and dairy products. This is completely different from the foods that the species typically consume, such as grasses, leaves, seeds and occasionally insects.”
This behavior allows the monkeys to continue eating calorie-dense foods that they find irresistible, just like humans. Mr Lemoine added: “Eating dirt may enable them to continue consuming foods that have negative effects on the digestive system but are as delicious to them as they are to us.”
to work46 soil eating events were recorded during 98 observation days published in Scientific Reports. The population averages around 12 such incidents a week – high for primates – and the three groups at the top of the Rock, where tourist contact is most intense, are responsible for more than two-thirds of the incidents. A unit without access to human food has never been seen eating dirt.
This habit shows signs of becoming a cultural tradition. Different groups prefer different soils: most prefer the distinctive red “terra rossa” clay, but one troop regularly searches for tar-clogged soil from roadside ditches. About 30 percent of the events occurred in groups, and 89 percent occurred while other macaques were watching; This points to social learning.
Mr Lemoine said: “The emergence of this behavior in macaques is both functional and cultural… entirely due to proximity to humans.”
He compared this to tool-use traditions in chimpanzees, but these were driven by the human environment.
Local authorities provide appropriate food for the monkeys at feeding stations and prohibit visitors from feeding them, but many tourists still offer or lose snacks. Junk food made up almost a fifth of the macaques’ diet during the study period.
While geophagy occurs in some human cultures and is seen in other primates for mineral uptake or toxin protection, no increase was seen during pregnancy or lactation in Gibraltar macaques, strengthening the junk food protection hypothesis. Direct observations have even caught animals eating dirt shortly after eating ice cream, biscuits or bread.
The findings highlight how cohabitation with humans has reshaped primate behavior and culture at Kaya, where macaques imported from North Africa have long been intertwined with Gibraltar’s history and remain a major tourist attraction.
Don’t try the earth trick at home.
