Stegastes beebei (Galapagos ringtail damselfish or southern whitetail major), is a species of damselfish found on coral and rocky reefs at depths between 0 and 15 m. They are somewhat territorial, and chase away small intruders. They are omnivorous, grazing on algae and nibbling at small crustaceans and the tentacles of anemones. They are oviparous, with distinct pairing during breeding. The eggs are demersal and adhere to the substrate. Males guard and aerate the eggs.