Monkeys Avoid Their Ill Friends


We as a species have a highly developed survival instinct. When we see a good friend, significant other, or family member looking sick, we think twice before embracing them or kissing them. If nothing else, we are not sharing our drink/food with them. Well, it turns out Mandrill monkeys are pretty similar to us in that regard. The mandrill monkeys, more commonly known as the groomer monkeys avoid grooming a member of their society if that member’s poop smells differently.

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These findings come from a study conducted in 2017, during which scientists tried to find out as much as they can about these primates and their secret lives.

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The research that provided this info is trying to bring us closer to understanding the evolution of social behavior. Unfortunately, parasites are a common occurrence in social groups which are as close as the mandrill monkeys are. Parasites as a species need to move from one host to another to survive, so it makes perfect sense that they thrive in environments where animals are less isolated. Social animals do have a way to circumvent this, but this is still an issue for many social groups, and scientists are trying to determine the exact connection between the social groups and parasitism.

There is a link between infectious risks and host density, what is not clear are the consequences and effects of parasitism on social interactions.

This is why the recent findings regarding mandrill monkeys are ideal. They as a species live in big communities which contain up to several hundred individuals. As their name suggests, they often groom one another, and this is the ideal situation for parasites to thrive. Grooming is even considered a social activity. Since they are not as developed as humans obviously, their idea of hygiene is different to ours. So, while grooming they resort to touching and licking one another which are excellent conditions for parasites to thrive in.

This is why scientists started tracking 25 of these monkeys and collecting their poop. What scientists found is that the mandrill monkeys do not ignore their infected members completely, but they do groom them less. As the number of parasites on a particular member grew, the less they were groomed. But as soon as scientists treated the monkey and reduced their number of parasites, the other monkeys started grooming them more. This makes perfect sense and keeping the infected monkeys down to minimum contact ensures that other members of the group do not get infected and that their young aren’t in any danger.

The reason scientists think this has anything to do with the poop of the monkeys is the fact that they avoid monkeys whose feces has a lot of protozoa in it. These samples have a particular chemical signature which is very different from the one found in healthy monkeys. The monkeys actively avoided poop that had unhealthy levels of parasites in it.

So, the hypotheses were correct, and the study proved that mandrill monkeys follow a social behavior similar to our own when faced with the possibility of infection. So, the monkeys do not isolate their infected members, but they do groom them less. This is especially true for grooming performed around the peri-anal area. This makes perfect sense due to the density of parasites that is located in this part of the monkey’s body.

This clearly shows that these monkeys can detect parasitized individuals and adapt their social approach accordingly. This is a great survival mechanic not present in many other species.

This has the potential to help us better understand how humans evolved, especially some of our social norms and interactions.

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Alexandra grew up dreaming of being a great science explorer. She always wanted to travel the world and explore some of the greatest science mysteries of the times. After high school, she studied chemistry in college and spent most of her summers working on research projects alongside her professors. It was there that Alexandra got clarity about what she wanted to do in the future. She now works full time in science research at a teaching university and is planning to go to medical school in a few years. She likes to stay up-to-date with the latest discoveries in science and share her love for science through her writing.


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