Zebras of the fish world use their stripes to dazzle predators

Zebras aren’t the only animal using black and white stripes to dazzle predators on the hunt for a tasty meal.

According to new research, the humbug damselfish – a species of fish that lives in coral reefs throughout the tropical waters of the Indo-Pacific region – also uses motion dazzle as a defence strategy.

The clever coral-dwelling fish might even change their behaviour to protect themselves from predators, depending on the striped patterns perceived around them.

“Our findings show that humbug damselfish adapt their behaviour based on their environment,” says Dr Louise Tosetto of Australia’s Macquarie University, lead author of the study in Peer J.

“In their natural habitat, when they encounter backgrounds resembling their own striped patterns, like branching corals, they tend to move closer and reduce their movement. This likely helps them blend in and stay hidden from predators.”

Though camouflage is well known for helping prey avoid the attention of predators, it can also help predators sneak up on their prey.

“When feeding outside the coral colony, where camouflage is less effective, [humbug damselfish] increase their movement and rely more on the confusing effects of their stripes, known as motion dazzle,” says Tosetto.

Motion dazzle protects moving prey by distracting predators through visual illusions, like the repetitive colour patterns of stripes, bands, and zig-zags. The moving stripey patterns of herding zebras makes it difficult for predators to work out the speed, distance, and direction of individual animals.

The researchers filmed humbug damselfish in fishtanks with various striped backgrounds to study how they might affect the fish’s ability to confuse predators.

They used anatomical data from the retinas of humbugs to understand how clearly the fish might perceive these differently striped patterns and used computer models to simulate how predators would perceive their movements.

When the background had clear, wide stripes that predators would easily perceive, the edges of the fish’s bodies became less distinct and harder to spot – thanks to their own stripes.

The combination of the humbug and background stripes also created motion dazzle, so predator models couldn’t accurately judge their speed or direction when moving.

But when swimming against a background that predators wouldn’t perceive clearly, the humbugs created more confusing motion cues by moving closer to the background and increasing their overall movement.

Senior author Dr Laura Ryan, also from Macquarie, says the findings show these fish have complex anti-predator strategies.

“This is an essential baseline study that provides new insights into the motion dazzle phenomenon,” says Ryan.

“Future research should investigate how factors like the water’s light-filtering properties and interactions with other damselfish might affect motion dazzle. The humbug damselfish offers a perfect model to explore these important questions.”