These colourful fish use their massive mouths to protect their love dens

When male sarcastic fringeheads get into a conflict, the spoils of war tend to go to the fish with the biggest mouth.

Sometimes, the colourful reef-dwellers will fight over territory, smashing their gaping maws together in what looks like a violent kissing contest. 

But most of the time, if one fish’s lips are big enough to strike fear into his challenger’s heart, that’s enough to prevent a physical altercation.

“They tend to live in rocky crevices or sometimes empty shells, and to protect these shelters and to retain them, they will often give this agonistic display by opening their mouth and trying to show the width and size of their mouth,” University of California San Diego biologist Zach Skelton told As It Happens host Nil Köksal.

“The point of the display, [as far as] we can determine, is to deter physical combat. So it’s basically showing, ‘Hey, I’m really big. Don’t mess with me.'”

Skelton co-authored a study about the male mouth-offs, which was published this month in the journal Ecology.

WATCH | Sarcastic fringeheads open their large mouths: