Small male fish use high aggression strategy

Published in the PLoS ONE journal this month, a study led by Dr Andreas Svensson of Linnaeus University in Sweden in collaboration with Monash University and the University of Turku, Finland, investigated what determined such aggression observed in smaller nest-holding males.

In this species, the eggs are cared for by their father who will aggressively defend his nest against intruders. Once he attracts a female back to his nest to lay her eggs, he fans the eggs with his pectoral fins keeping them oxygenated. The researchers were surprised to find that small nesting males were more aggressive toward intruders than larger males.

Study co-author Dr Bob Wong, a Senior Lecturer at Monash University's School of Biological Sciences and an expert in behavioural and evolutionary ecology, said to attack early may be a beneficial strategy for small males, because they avoid revealing their inferiority to the intruder.

"In the animal world, competing males are expected to partake in a drawn out escalation of aggression, to avoid the risks of being injured by a superior opponent," Dr Wong said.

"We found the aggression of males was not affected by the presence of females and perceived mating opportunities or larger male intruders. Instead their aggression was related to their size.

"In particular, smaller males attacked sooner and with greater intensity compared to larger males, suggesting that nesting desert goby males used routine, rather than conditional, strategies for initiating aggression."

Dr Svensson said if intruders were more likely to flee than retaliate, small males could benefit from attacking intruders before they had an opportunity to assess them.

"The only hope for a small male may be that an intruder would then leave, without a fight," Dr Svensson said.

The overly aggressive males were dubbed 'the Napoleon complex' after the French general Napoleon Bonaparte who was thought to compensate his allegedly short stature with an aggressive personality.

The hardy desert goby can tolerate extreme conditions and can be found in water twice as salty as the ocean and survive huge fluctuations in temperature -- all important survival skills for a fish living in the desert.

The research was presented at the International Behavioural Ecology Congress in Sweden earlier this month.