Males of this species aggressively compete for females, and once a bigger male has mated with a female, he’ll usually stay close to prevent other males from mating with her. When the female is ready to lay her fertilized eggs, she’ll seek out a coral crevice protected from currents and predators and will lay eggs multiple times in the same place. The male will continue to guard her for a short time after she’s finished laying, and then move on, presumably to find other females to mate with.

But on recent dives in Egypt’s Red Sea, biologist Eduardo Sampaio observed something strange: A dominant male that had already paired with a female would scare off his rivals