Same-sex behaviour among wild female gorillas has been documented for the first time and the Australian behind the study believes it is motivated by sexual arousal.

Associate Professor Dr Cyril Grueter, a primate expert from the University of Western Australia, stumbled on the behaviour when studying the feeding ecology of mountain gorillas in Rwanda,

This is the first time two wild female gorillas have been documented engaging in sexual behaviour. Credit:University of Western Australia

It was after a miserable period of rain in the jungle and female gorillas enjoying the sunshine were trying to court the male but, Dr Grueter said, he had no interest in them.

That was when he first noticed the females engage in activity with each other.