They were grooming each other, sniffing each other's genitals and vocalizing to each other in soft, high-pitched calls, similar to the sounds baby koalas make. They also appeared to be playing.

Of Observations, A Researcher Observed Three Male Koalas Engaging In Unexpected "Affiliative" Behaviors . Credit to ...

They were grooming each other, sniffing each other’s genitals and vocalising to each other in soft, high-pitched calls, similar to the sounds baby koalas make. They also appeared to be playing.