Gibraltar monkeys have recently been observed engaging in a surprising behavior: eating dirt. This habit may be a response to the adverse effects of human junk food, as detailed in a study published in Scientific Reports.
This unusual eating behavior seems to help the monkeys manage digestive issues caused by tourist treats, particularly when lactose-intolerant individuals consume ice cream.
According to Dr. Sylvain Lemoine, a biological anthropologist at the University of Cambridge, “Food consumed by Gibraltar’s monkeys is often high in calories, sugar, salt, and dairy, which is starkly different from their natural diet of herbs, leaves, seeds, and occasional insects.”
“Eating dirt may enable them to indulge in these unhealthy yet appealing foods, similar to how humans enjoy them,” he added.
A research team studied 230 monkeys in Gibraltar, finding that each monkey consumed dirt approximately 12 times per week.
Interestingly, geophagy (the act of eating soil) decreased by 40% during winter compared to the tourist-heavy summer months.
Furthermore, researchers noted that monkeys with a higher frequency of human interaction—and consequently junk food consumption—exhibited more geophagy. In fact, three groups of eight macaque monkeys residing in tourist areas accounted for 72% of geophagy incidents.
Conversely, the only group of monkeys without access to tourist-provided snacks was also the group that did not eat soil.
The study concluded that geophagy is directly linked to junk food, suggesting that it acts as a gut health supplement, mitigating the negative effects of cookies, ice cream, and other snacks on the monkeys’ microbiomes.
“Macaques may have developed this behavior to protect their digestive systems from the high-energy, low-fiber snacks that can lead to stomach issues in primates,” explained Dr. Lemoine.
“Soil can serve as a barrier in the gastrointestinal tract, reducing the absorption of harmful substances, and may even provide beneficial bacteria that assist in gut health.”
Such geophagy isn’t unique to Gibraltar’s monkeys; ring-tailed lemurs consume dirt an average of 16 times a week, while East African chimpanzees do so about 14 times. This behavior is also observed in human cultures, particularly during pregnancy.
Geophagy is notably rare among Barbary macaques of North Africa, the ancestral population of Gibraltar’s monkeys.
Remarkably, a group of monkeys at Hong Kong’s Jamshan Country Park has been documented eating dirt over 33 times a week, likely due to their high consumption of human junk food.
Dr. Lemoine emphasized the study’s implications regarding human influence on animal behavior and culture.
“Gibraltar’s monkeys represent a unique case of human-primate interaction, offering valuable insights into how anthropogenic environments impact primate behavior and culture,” he noted.
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Source: www.sciencefocus.com