Relationship with parasites
Wild animals, such as monkeys, are often carriers of parasites. Biologists have long assumed that these infections do not significantly affect the health of the animal. What is most surprising, however, is that the parasites researcher Wren was studying they are not transmitted through social contact.
These gastrointestinal parasites are generally transmitted through substances in the environment or contaminated soil. However, research shows that they can significantly affect social behavior of an individual.
The team of scientists followed three troops of vervet monkeys across South Africa. By cataloging the interactions and toilet habits of monkeys and by cross-referencing information from infection of fecal samples, they were able to conclude that infected monkeys spent less time grooming other monkeys.
In addition, according to the researcher, there is no way to know which monkeys are infected just by observation, since often no other signs of infection (beyond social behavior).