The present-day grunions have inherited this dangerous breeding practice from a myriad of earlier generations, but why should they have adopted it in the first place remains a mystery. Perhaps long ago there were fewer predators on the shoreline, so the eggs were safer on the beach than at sea. If so, then at that time, the risk was worth taking. Among the blueheaded wrasses living on the western Atlantic coral reefs, there are two types of males. Large and brightly coloured males that are about 6 inches long and compete for mating sites with each other and pair up with a succession of females are in a smaller proportion to the smaller, yellow males that spawn in groups of females.
Blueheads are a wrasse species that feeds on small marine animals.
The large, blueheaded breeding males actually start life as diminutive, dull-coloured females. Females may also be stimulated to change into males if the number of females in a particular community increases greatly. They start life as males, but change to females when they are fully grown. These fish live among the sea anemones and feed on planktons minute plants and animals. A family group is dominated by a large female who mates with the males of her group.