For smaller goby fish males, an aggressive display can distract an intruder from noticing his size. "The only hope for a small male may be that an intruder would then leave, without a fight," says study leader Andreas Svensson. (Credit: P. Andreas Svensson)

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A new study published in PLoS ONE this month investigates what determines the aggression scientists observe in smaller nest-holding males.

The male desert goby takes care of the eggs, and will aggressively defend his nest against intruders. Once he attracts a female back to his nest to lay her eggs there, he fans the eggs with his pectoral fins to keep them oxygenated.

The researchers were surprised to find that small nesting males were more aggressive toward intruders than larger males.

Attacking early may be a beneficial strategy for small males, because they avoid revealing their inferiority to the intruder, says co-author Bob Wong, senior lecturer at Monash University’s School of Biological Sciences and an expert in behavioral and evolutionary ecology.

“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,” says Wong.

“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.”

Study leader Andreas Svensson of Linnaeus University in Sweden says that 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,” Svensson says.

The overly aggressive males seem to have “Napoleon complexes,” the phenomenon named for the French general Napoleon Bonaparte, who was thought to compensate for 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 can survive huge fluctuations in temperature—important survival skills for a fish living in the desert.

The research was presented at the International Behavioral Ecology Congress in Sweden earlier this month. Researchers from the University of Turku in Finland also contributed to the study.

Source: Monash University