In most species, a male specimen will usually don’t invest a lot of time or energy in caring for young when there is a good chance that he is not their father. There are how ever exceptions to this rule, such as the Ocellated wrasse.

Yale University researchers studying the breeding behaviour of this Mediterranean fish have found that a male Ocellated wrasse is more likely to care for the offspring when there is grave doubt about who actually fathered them.

The study also showed that female Ocellated wrasse will deposit more eggs in a nest where the nesting male is surrounded by non-nesting “sneaker males”; males who are keen to fertilize the eggs but have no plans ever caring for the offspring. Females will also deposit more eggs in nests where there are already large numbers of offspring.

“Parental male oscellated wrasse are more likely to care for offspring in this sperm-filled  environment than in nests in which there is less sexual competition”, said Suzanne H. Alonzo, assistant professor of ecology and evolutionary biology and co-author of the study.

Even though the caring male has a greater chance of ending up taking care of someone else’s offspring if he allow other males to hang around, he still benefits from having a lot of “sneaker males” near his nest since it will make the females deposit more eggs.

“While our simpler theories have trouble explaining the diversity of what we observe in nature, these patterns do have explanations,” Alonzo said. “The paper suggests we may have oversimplified the evolutionary dynamics of how these things work.”

The paper has been published in the edition of the journal Proceedings of the Royal Society of London. The study was carried out by Suzanne H. Alonzo, assistant professor of ecology and evolutionary biology and Kellie L. Heckman, a postdoctoral fellow in the department.