In late April, French President Macron was the first world leader to visit Donald Trump at the White House. Several notable scenes were captured on camera, the most notable being the moment when Trump brushed a flake of dandruff off Macron's suit jacket. Surely this was monkey behaviour, right? But why do monkeys groom each other, anyway?
In this article (Dutch) several primatologists analysed this case of what very much seemed to be ‘monkey behaviour’. For instance, cognitive psychologist Mariska Kret of Leiden University had this to say on the subject: ‘Grooming others is something you do to show your affection.’
Animal trainer Marlies has noticed this same type of behaviour in the three types of monkeys living at BPRC: crab-eating macaques, rhesus macaques and marmosets. ‘Grooming others is an act of friendship, and in addition, we often observe that monkeys groom each other to make up after a fight. To bond after a conflict. They are group animals who fight a lot, but must be able to get along again in the end. As a result, you will often see them reconcile in this way.’
Sign that everything is well
Marlies and her colleagues have also noticed that grooming relaxes the animals, both the party doing the grooming and the party receiving the grooming. ‘You can see their level of anxiety decrease when they are grooming each other. To us, this is a sign that everything is well between two monkeys who share an enclosure – for instance, at the experimental facility. It is important to us that they really get along, but sometimes two personalities just happen to be incompatible. This doesn't happen very often, but it does happen. In such cases the monkeys are separated.’
In order to determine whether or not two monkeys get along, Marlies and her colleagues will sometimes use video footage. ‘Sometimes this will show that they do not engage in friendly behaviour when we are around. They don't show their genuine behaviour until we are gone. Sometimes these pairs will really seek each other out when we are not around. They will be totally at ease and relaxed with each other. The footage often shows they are actually good buddies.’