That sounds interesting. Gorrillas are intelligent social animals like us (but nicer) Animals can be shy and show signs of similar problems to humans.

My mate has a dog a chihuahua adopted at the age of 5 months. She is generally a happy little thing but now and again she is clearly depressed. Tail down, unsociable, squeaks if touched (no matter how gently) this can go on for weeks, then, suddenly shes back to her usual happy self. Vet said dogs can be given anti depressants, but my mate has decided not to medicate unless it gets much worse.

Bipolar dog?

Animals, particularly the social ones that live in groups feel the same emotions as we do.

Humans think they are so 'special' above all other creatures but we are not.