Cuttlefish use camouflage to stalk unsuspecting crabs

In the waters of Southeast Asia, broadclub cuttlefish have a unique method for surprising unwary crabs. These color-shifting predators blur the line between stealth and spectacle by passing dark stripes down their head and arms during the last few seconds of a hunt.

This discovery comes from a recent study led by Dr. Matteo Santon, an expert in the University of Bristol’s School of Biological Sciences. The researchers examined a dynamic camouflage tactic that challenges previous ideas about how animals remain hidden while moving.

“Maintaining camouflage while moving is a challenge faced by many predators. Some exploit background motion to hide while hunting, and others may use coloration and behavior to generate motion noise that impairs detection or recognition,” noted the researchers.

Cuttlefish camouflage distracts prey

The experts recorded cuttlefish targeting crabs and noticed a striking display that seems to distract the prey’s motion-detection system. They introduced a high-contrast moving pattern that travels down the predator’s body, starting when the cuttlefish is about 3.2 ft from its target.

By harnessing strong downward motion cues, the cuttlefish weaken the usual signals that alert the crab to danger.

“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,” said Dr. Santon.

Why crabs miss cuttlefish attacks

Most crabs rely on clues like looming shapes to signal an attack is coming. This approach makes sense when a predator’s silhouette expands as it nears.

The broadclub cuttlefish undermines that system by overlaying downward stripes, obscuring the expansion cue and sowing confusion in the crab’s visual network.

Stripes seem obvious to our eyes. But to a crab with limited visual resolution, the repetitive downward flow acts like static that clouds the predator’s actual speed and position.

The scientists tested this effect with lab experiments that displayed animated shapes on screens, confirming that the moving pattern often dulled the crabs’ defensive reactions.

Using camouflage on the move

“Most cuttlefish rely on stealth to sneak up on prey. Due to their fast color-changing skin, these remarkable animals have a wider range of options than most when it comes to camouflage while moving,” said Dr. Martin How, senior author from the University of Bristol.

These color-changing animals can shift at a moment’s notice to blend with seafloor textures or dazzle potential victims. This flexibility lets them adapt to different conditions, whether they need to hide against coral or outsmart prey with moving stripes.

Broadclub cuttlefish frequently hold their arms out when they mount these final attacks on crabs. This flattened pose reduces the expected radial cues of an oncoming shape.

The rhythmic stripes flow down the arms, overshadowing any clues that might give away the cuttlefish’s real approach path.

Insights into cuttlefish camouflage

Some predators blend in by matching seaweed sway or drifting shadows. Others rely on sudden bursts of speed or chaotic patterns that throw off a target’s aim.

Broadclub cuttlefish have raised the bar by adding a directional motion pattern that contradicts what prey typically expect from an approaching threat.

This hunting approach offers new insights into the way motion-based camouflage can evolve in complex habitats. The wide range of cuttlefish skin patterns suggests there may be more to learn about how they choose between different tactics for different targets.

Motion-based camouflage strategies

The researchers speculate that other cephalopods may use comparable tricks. The team has also considered that certain crab species become desensitized to repetitive passing stripes after repeated exposure.

Further research could clarify how widespread these motion-based strategies are among ocean predators that rely on color adaptation.

Field researchers are excited to see if conditions like light levels, water clarity, and the presence of competing predators push cuttlefish to alter their camouflage displays in real time. Such flexibility might shape how prey species respond and whether they can develop new defenses.

The study is published in the journal Science Advances.

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