Species in the Gobiidae sometimes form symbiotic relationships with other species, such as with burrowing shrimps. The shrimp maintains a burrow in the sand in which both the shrimp and the fish live. The shrimp has poor eyesight compared to the gobiid, but if it sees or feels the fish suddenly swim into the burrow, it will follow. The fish and shrimp keep in contact with each other, the shrimp using its antennae, and the fish flicking the shrimp with its tail when alarmed. These gobiids are thus sometimes known as "watchmen gobies" or "prawn gobies". Each party gains from this relationship: the shrimp gets a warning of approaching danger, and the fish gets a safe home and a place to lay its eggs. Only the alpha male and female reproduce, other fish in the colony eat sparingly to resist being eaten by the alpha male or female. This way, only the largest and fittest are able to reproduce.