On the Rock of Gibraltar, one of the most classic scenes that can be found without a doubt is that of the Barbary macaqueswho seem to be the absolute kings of the entire terrain. Here it is quite likely to see tourists end up stealing a piece of sandwich, chips or a sweet that they have in their hands, especially when the rules are not followed that are marked. But this, which may have its funny point, the truth is that it generates quite a few alterations in the animals, to the point of needing to eat dirt.
It has been studied. That a macaque takes a bag of Doritos from a tourist and begins to eat it, among many other types of junk food, is something that has focused the attention of science. And it has reached such a point that it has materialized in a study published in Scientific Reports where numerous continuous episodes of geophagy have been documented among these primates.
This is nothing more than the usual consumption of red soil, which is known as terra rossa, and even, in some specific groups, a strange mixture of dirt and tar.
Its consequences. What at first glance may seem like simple animal curiosity is actually a survival mechanism, as researchers have found a statistical correlation between the consumption of this junk food, loaded with sugars, salt and dairy, and the frequency with which they eat the earth.
In fact, the data shows that this practice increases in summer, when there are a greater number of tourists in the area, and decreases drastically when the influx of people and, therefore, the availability of junk food in the area decreases.
Why do they do it? Here we must take into account that the stomachs of these macaques are not prepared for the junk and processed food that humans consume. This is why the earth can act as a gastric cushioning system and can be compared in our minds to a stomach protector. After a heavy meal, macaques use clay to purge themselves, absorb toxins and relieve the digestive discomfort caused by our diet.
In addition to providing them with certain minerals that junk food lacks, scientists point out that swallowing dirt helps them try to rebalance an intestinal microbiome that has been altered by the excess of salt and sugar.
A cultural tradition. The most interesting finding of this research is that eating dirt is not a mere isolated instinct, but has become an anthropogenically induced tradition of primates.
That is to say, we are dealing with a behavior of social transmission, since the macaques learn from each other that eating dirt relieves the belly pain after stealing an ice cream from a tourist. This, logically, is a cultural component of self-medication that has arisen purely and exclusively due to the alteration of their environment at the hands of human beings, demonstrating the great capacity for adaptation that they can have to any situation that comes upon them.
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