Why do gorillas groom each other?

Why do gorillas groom each other?

The grooming that takes place between gorillas is a very, very important part of their very, very complex social structures. It's a way that the gorillas are able to be very relaxed with each other. The dominant male gorilla will only allow certain females to groom him, and he will only choose to groom other females gorillas. They won't just all groom randomly. It's quite a particular sort of concept, if you like, within their social hierarchies. But actually here at the zoo, we find that once a gorilla accepts a zookeeper, and accepts the trust of a zookeeper, it's possible for the keepers themselves to actually groom the arm of the gorilla, just to build up the relationship over a long period of time.