Trending Now - Gibraltar Monkeys Consume Soil to Counteract Tourist Diets
WHO:
Gizmodo - Sylvain Lemoine, senior study author and biological anthropologist at the University of Cambridge.
Phys.org - Researchers from the University of Cambridge.
WHAT:
Gizmodo - The study documented 46 instances of geophagy among the Gibraltar monkey population.
Phys.org - The behavior of soil-eating was especially common in areas with heavy tourist traffic and peaked in summer 2024, when visitor numbers are highest.
Phys.org - One group of monkeys with no access to human food showed no instances of soil-eating at all.
Gizmodo - Monkeys in Gibraltar are regularly eating dirt, a behavior known as geophagy, to soothe their stomachs from junk food consumed from tourists.
Phys.org - The study observed that troops of macaques in Gibraltar are self-medicating with soil to help digest tourists' sweet and salty snacks.
Gizmodo - There are an estimated 200 to 300 Barbary macaques (Macaca sylvanus) in Gibraltar.
WHERE:
Gizmodo - Gibraltar, a British-owned territory located at the southern tip of the Iberian Peninsula bordering Spain.
Phys.org - Gibraltar, the only free-ranging monkey population in Europe.
WHEN:
Gizmodo - The findings were published on April 20th, 2026, in the journal Scientific Reports.
Gizmodo - The long-term study, known as the Gibraltar Macaques Project, was started in 2022.
WHY:
Phys.org - Researchers propose that human food, being not adapted to the monkeys' natural diet, triggers upset stomachs and potentially microbiome disruption, which is buffered by the soil components.
Gizmodo - The monkeys are consuming dirt likely as a way to counteract the gastrointestinal symptoms caused by the junk food provided by tourists.
Gizmodo - The study suggests that the consumption of junk food is disturbing the monkeys' gut microbiomes.
HOW:
Phys.org - The study suggests that the behavior may be socially learned, with different groups of monkeys favoring specific types of soil, and most soil-eating occurring in the presence of other macaques, allowing younger individuals to observe and copy.
Gizmodo - Researchers tracked local populations of macaques and observed that dirt-eating was most common in troops near tourist areas.
Gizmodo - The team integrated reporting and recording of dirt-eating behavior into their regular population censuses and individual follows.
(UPDATED April 22, 2026 23:15 UTC)
A new study has documented 46 instances of geophagy, or soil-eating, among the Gibraltar monkey population, particularly in areas with heavy tourist traffic, where this behavior peaked in summer 2024. Researchers believe that the consumption of human food, which is not suited to the monkeys' natural diet, may lead to digestive issues that the soil helps alleviate. The study also suggests that this behavior might be socially learned, as different groups of monkeys prefer specific types of soil, with most soil-eating occurring when younger individuals observe and imitate their peers.
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(UPDATED April 22, 2026 21:24 UTC)
Researchers from the University of Cambridge have found that Barbary macaques in Gibraltar are regularly eating dirt, a behavior known as geophagy, to help soothe their stomachs after consuming junk food from tourists. The study, published on Monday, in the journal Scientific Reports, suggests that this dirt consumption is a self-medicating response to gastrointestinal issues caused by the sweet and salty snacks provided by visitors. The long-term research, which began in 2022, tracked local macaque populations and revealed that this behavior was most prevalent in troops located near tourist areas.