Sharks may be social or solitary animals living on their own, depending on the species. Since they are equipped with teeth at birth, they do not need to rely on each other for survival.
Sharks most likely join together in communities for protection and to avoid aggression with other sharks, according to Johann Mourier, a scientist at the Center for Island Research and Environmental Study. The observed behavior of hammerhead and blacktip reef sharks has even indicated that such species may have complex social hierarchies.
Sharks traveling in groups are most common during mating season and periods of migration, though some species also tend to hunt together in groups.