Maintaining camouflage while sneaking up on prey is a challenge faced by many pursuit predators and a skillset mastered by only a few. Among them is the cuttlefish, whose tactic – it transpires – is to employ a dynamic skin display in the very last moments of its approach, designed to make it ‘invisible’ to their target.

These are the findings of researchers from the University of Bristol and  those recently published in Science Advances in which it was uncovered that the broadclub cuttlefish uses a ‘novel form of motion camouflage’ by disguising their hunting manoeuvres with a stripy display.

The publication provides an alternative theory to the previously accepted notion that cuttlefish uses a form of ‘hypnotisation’ to capture its prey, suggesting instead that its choice of dinner, more likely ‘just doesn’t even see the cuttlefish’ but rather a confusing pattern movement.

It’s well-established that the cuttlefish is uniquely armed with fast colour-changing skin, passing dark stripes downwards across their head and arms in the very final moments of their approach. It’s now believed, however, that rather than an attempt to ‘mesmerise’ its prey into bafflement, the display is designed to “overwhelm their visual system” and render them unable to detect the looming cues of a predator about to pounce.

The cuttlefish is not the only species to engineer its motion in such a way to disarm its potential prey. Both dragonflies and falcons have been known to fly in a manner that tricks the visual system of their target, making them seemingly ‘invisible’. Meanwhile snakes, stick insects, and even some spiders have been recorded ‘swaying with the movement of vegetation’ to blend in with their surroundings during a hunt.

These tactics do, however, more generally make these species outliers in the general deployment of camouflage.

The study’s lead author, Dr Matteo Santon from the University of Bristol’s School of Biological Sciences, has suggested that the cuttlefish’s advanced camouflage skills are likely deployed in a similar fashion when hunting its prey on the move.

“Camouflage has predominantly been studied as an adaptation that prey use to hamper their detection or recognition from predators, and almost exclusively focused on still prey as motion tends to disrupt camouflage,” he said.

Most cuttlefish rely on stealth to sneak up on prey. Yet it’s due to their fast colour changing skin that they are armed with a wider range of options than most when it comes to camouflage while moving. From a crab’s point-of-view, the study suggests, the visual system of the prey is left ‘mesmerised’ by the strong motion of the stripes deployed by the predator.

“To our eyes this dynamic display looks very conspicuous, standing out strongly from the background,” said Dr Santon. “But it is exploiting the effect of the strong dynamic motion cues produced by the rhythmic passing stripes to deceive the prey.”

To study the efficacy of motion camouflage on potential cuttlefish prey, Santon and his team first tethered shore crabs to a Styrofoam treadmill sitting before a monitor, which played various stripe patterns both similar to and dissimilar to the patterns displayed by cuttlefish.

It was found that the crabs displayed a strong reaction to high-contrast patterns but reacted the least to those of stripes moving in a downward direction. 

Putting the developing theory to the test using real cuttlefish, a multicamera rig recorded 17 individual cuttlefish using stripe hunting displays 28 times, writes Courthouse News. From this, the scientists were able to observe and record what a typical hunting technique would look like: a cuttlefish would spot its prey, rush toward it, and then switch to a passing stripe display in the final phases of attack as it approached the target.

But this isn’t the only tactic in the cuttlefish’s arsenal when it comes to the hunt. This species can produce at least three other types of elaborate hunting displays.

“This is an astonishing variety of adaptations for sneaking up on prey,” said Dr Santon. 

For the team at the University of Bristol, focus will not shift towards how these other displays function as Dr Santon and his research partners begin to investigate just what makes cuttlefish choose one hunting display over another. 

“It was a truly magical experience seeing this species hunting in the wild for the first time,’ continued Dr Santon. “Watching this cuttlefish hunting with the passing-stripe display is like being mesmerised by the tricks of a skilled illusionist.”

The paper – titled, ‘Stealth and deception: adaptive motion camouflage in hunting broadclub cuttlefish’ – is authored by Matteo Santon, Jolyon Troscianko, Charlie D. Heatubun, and Martin J. It is now published in Science Advances.

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