Among color-changing sea creatures, the ability to flash from one hue to another more typically comes in handy for evading predators rather than hunting prey. But the striped marlin, new research shows, uses its mutability not only to pursue food, but to hunt collaboratively. Drone footage of group-hunting marlin (Kajikia audax) portrays the first rapid color change in such teamwork-oriented predators, described in a paper published today in the journal Current Biology from researchers in Germany and the United Kingdom.
Striped marlin can change their exterior from blue-gray to high-contrast stripes in mere moments thanks to cells called iridophores, stacked with thin, crystalline protein plates that act as multilayer reflectors. While we’ve known that marlin can change color this way, this finding introduces how the ability aids hunting behaviors. Changing hues may also have a dual function that lets marlin both coordinate attacks and ambush their prey.
“Color change in predators is rare, but especially so in group-hunting predators,” lead author Alicia Burns, a postdoctoral biology research fellow at Humboldt University, said in a press release. “Although it is known that marlin can change color, this is the first time it's been linked to hunting or any social behavior.”
Burns’ team analyzed 12 high-resolution video clips portraying 24 marlin attacks on a school of sardines off the coast of Magdalena Bay, Baja California Sur, Mexico. They noticed that in the moments before charging, a marlin’s stripes significantly brightened, while those hanging back remained blue-gray. To measure how hunting role and color correspond, the team quantified the stripes’ contrasting brightness on two attacking marlin and one non-attacker. The attacking fish always boasted the brightest contrast immediately before attacking and dimmed once finished, which suggests stripe intensity plays a critical role in hunting behavior.
Burns and her colleagues gleaned that brightening and dimming their stripes allows marlin to reliably signal to each other when one is going to attack, which prevents accidental collisions. This change may also dazzle their sardine prey to disrupt any escape attempts.
This discovery may indicate that more predators use color changing than previously thought. It also suggests that marlins’ communication channels are more complex that we suspected. The team hopes to determine whether marlin still change color when hunting alone, and whether similar transformations aid other predatory fish.
