Koalas

Koalas have a scent gland on their chest that they use to mark their territory by aggressively hugging trees. At the culmination of the violent tantrum which is koala coitus, the male leaves a seminal plug which blocks the female's multiple vaginas from being entered by the hemipenis of another koala. Female koalas are also infamous for engaging in lesbian sex. Females often overlook males and participate in sexual acts with other females, sometimes in orgies with up to 5 female koalas. Also, koalas are riddled with chlamydia.