On the Rock of Gibraltar, the famous macaques no longer just follow their natural diet. Under normal conditions, these primates feed on fruit, leaves, roots and insects, but the constant presence of visitors has radically changed their habits. Today, ice cream, packaged snacks, chips and industrial sweets, foods rich in sugar, fat and dairy products often end up in their hands.
A mix that their body is not designed to handle. The result is an increase in digestive disorders, aggravated by the almost total absence of fiber and the difficulty in metabolizing lactose, which adult primates cannot tolerate. Although it is forbidden to feed them, the data is clear: around 20% of the time dedicated to food is linked to what they receive or take away from human beings. A change that is anything but marginal.
The macaques’ response: eating dirt to “cure” themselves
Faced with this altered diet, macaques have developed a strategy that is as unusual as it is effective: geophagy, or the intentional ingestion of earth. Scientists have observed numerous episodes in which animals consume clay, particularly red earth, often shortly after ingesting human food.
This behavior is not random. The earth acts as a sort of natural detox, creating a barrier in the digestive system that helps limit the absorption of harmful substances and reduce symptoms such as nausea or diarrhea. It also provides useful minerals and bacteria absent in industrial foods. According to the researchers, the most solid hypothesis is precisely that of the purifying function, rather than that of nutritional integration.
A social behavior that becomes “tradition”
What makes this phenomenon even more interesting is its social character. Geophagy is not an isolated gesture, but a behavior that is observed, imitated and transmitted within groups. Some macaques develop real preferences for specific types of soil, creating shared habits that recall small cultural traditions.
It is no coincidence that the groups most exposed to contact with tourists are also those who show the highest frequency of ingesting soil. On the contrary, populations less accessible to visitors rarely exhibit this behavior, confirming the direct link between human presence and changes in animal habits.
The human impact goes beyond diet
Experts point out that human interference doesn’t just change what macaques eat, it also impacts health, behavior and social dynamics. Geophagy, despite being an adaptive response, represents a clear signal: these animals are trying to compensate for the effects of an unnatural diet. A fragile balance, which shows how tourism can influence even the deepest aspects of animal life.
You might also be interested in:
