During the breeding season, males compete for access to females. Such competition can take the form of fighting other males or of herding females to prevent access by other males. In Shark Bay, male bottlenose dolphins have been observed working in pairs or larger groups to follow and/or restrict the movement of a female for weeks at a time, waiting for her to become sexually receptive. These coalitions, also known as male reproductive alliances, will fight with other coalitions for control of females. Humans and dolphins are the only species that share this type of "gang formation" habit as a form of cooperation.