A cat is friends with a cat, a dog is friends with a dog? Not necessary. There are exceptions, though rare. Moreover, friendship is truly tender and reverent.
As an example, here is this amazing video in which a little monkey is literally babysitting a feathered friend, a yellow duck, nailed to its enclosure. The monkey herself is still a child, but this does not prevent her from helping her newfound playmate.
An equally interesting situation arose in one of the zoos in Israel. there lives a monkey named Niv, who is very worried about boredom and her loneliness.
With her appearance, she did not succeed in contact, but the solution to the problem came by itself – in the form of a chicken that wandered into the territory of the macaque’s residence, which Niv not only did not expel, but also took under his protection.