Fish learn their facts of life from elders.

Fish learn their facts of life from elders

A biologist says he has shown experimentally for the first time that younger members of an animal species learn where to mate from older ones, not necessarily from environmental cues. Robert R. Warner of the University of California, Santa Barbara, believes the results of his work with bluehead wrasses, fish inhabiting coral reefs north of Panama, should generally caution scientists against explaining mating habits solely on the basis of the distribution of food and other resources.

Warner experiments, described in the Oct. 20 NATURE, involved introducing younger wrasses to 22 Caribbean patch reefs previously occupied by older members of the species to determine if the newcomers would use established mating sites.

Before transporting younger fish to new reefs, Warner removed all previous occupants from some sites, but only some from others. At the reefs where older wrasses remained, the newly introduced fish continued using the mating sites frequented by their elders.

At the reefs no longer housing older wrasses, the newcomers showed no preference for the established sites. "Old sites and previously unused sites were equally likely to be used" by the new inhabitants, Warner told SCIENCE NEWS. For experimental controls, Warner reintroduced some fish to their home reefs after the reefs had been cleared of all wrasses, finding the native fish returned to their established mating sites.

Had the control groups mated at different sites, Warner could not have concluded that the younger wrasses choose where to mate by observing their elders. The behavior of the fish reintroduced to their home reefs also suggests that transporting them in nets did not affect mating-site choices, he says.