The bandit angelfish, and most other marine angelfish, are protogynous hermaphrodites. This is caused by the territorialism of males and the females they accompany. One male is often in charge of many females, or a harem. These males are very territorial of the harem, thus, when the male dies and the harem is in need of a new leader, a female changes sex and becomes the new male leader of the harem. Bandit angelfish are mostly females as juveniles; however, some change sex during maturation and become males. This is why there is a large ratio of female to males within this species.