Giant reef fish headbutt their rivals for sex

by EWEN CALLAWAY

First sighting of ramming behaviour in bumphead parrotfish during competition for females.

Trespassers on the mating grounds of male bumphead parrotfish soon learn a hard lesson. The reef-munching fish fend off competing males using aggressive headbutting — a form of behaviour that has never previously been seen in the species. A team of US researchers reveals the surprising finding in the journal PLoS ONE this week1.

Growing to a weight of more than 75 kilograms and up to 1.5 metres in length, the giant bumphead parrotfish (Bolbometopon muricatum) is one of the heftiest reef fish in the world — but also one of the most shy around humans.

“These really are underwater buffalos, gentle giants that play a critical role in coral reef ecology. But when reproduction is involved, it is time to fight,” says David Bellwood, a marine ecologist at James Cook University in Townsville, Australia, who was not involved in the study.

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