Aggressive Fish Beat Bigger Fish In Fights, Says ‘Napoleon Complex’ Study

Aggressive fish, not bigger fish, are the winners when a fight gets physical over food. Sheer force of personality is what really counts. That’s the surprising result of a new study published in the April journal Behavioral Ecology and Sociobiology.

The study was performed on an oh-so-innocent little fish called the sheepshead swordtail, Xiphophorus birchmanni. There’s a picture down below of one looking all cute and innocent, like butter wouldn’t melt in its helpless little mouth.

But the reality of the species is quite different. Dr. Alastair Wilson from the UK’s University of Exeter said that the research team thought about the Napoleon complex as they studied the fish food fights.

“[S]mall fish with an aggressive personality are capable of defeating their larger, more passive counterparts when it comes to fights over food.” he said. “The research suggests that personality can have far reaching implications for life and survival.”

Napoleon complex or so-called short man syndrome isn’t an official condition recognized by psychologists. However, it’s popularly understood to describe a short person, usually a man, who compensates for his small size by being overly aggressive or dominating to others around him.

In the case of the sheepshead swordtail, it was already well-known that individuals can vary quite a bit in size. However, instead of assuming that the bigger fish were the bullies, the researchers would place two fish into a tank and then simply observe what happened.

Females were pretty easy-going, rarely assaulting the other individual in the tank over food.

However, many males would boldly attack another fish in the tank. And it wasn’t always the big fish that started the problem. Instead, a smaller fish was frequently the bully.

And you couldn’t just look at the fish and bet that the bigger fish would win the battle. Actually, the more aggressive fish would usually win, regardless of who was bigger.

Over time, as a result of winning more food fights, the more aggressive fish would grow bigger.

But the aggressive fish weren’t the bigger fish in the beginning. They just had the bigger personality.

sheepshead swordtail

[sheepshead swordtail fish photo courtesy University of Exeter]

[lionfish photo by Elaine Radford]