These territorial fish are regulars of the reef environment. Gray triggerfish can be seen in small groups on reef and/or bottom structure and will approach divers and even bite them with powerful teeth and jaws. Because of their very tough dermal layer their ribs are greatly reduced in size and thickness, their rugged skin protects them from penetrating teeth and spines of other fish. They actually form mating pairs and will build and guard a nest containing an egg mass. Gray triggerfish are so named for their main spine atop their head. It can lay flat or stand erect thus allowing the fish to lodge themselves in a reef crevice to avoid being pulled out by a predator.