Spotted hyenas have a complicated greeting ceremony, involving a variety of interactions using scents and physical gestures. These are only used by certain individuals in a clan and are uncommon between females and low-ranking males. They help to reduce stress in the group. Females are very aggressive and, to help them dominate their clans, they have developed false genitals to look like males. They will fight other females to win over and mate with favoured males. Hyenas are very vocal and their wails - howling screams and "laughter" - can inform other clan members of a food source from up to 5km away.