Study reveals crabs rely on camouflage tricks

Crabs from a single species rely on different camouflage techniques depending on what habitat they live in, a recent study has found.

Researchers compared the colour patterns of common shore crabs and rock pools crabs. They found that shore crabs from mudflats closely matched the appearance of the mud they live on, while rockpool crabs did not match the background but instead relied on disruptive colouration, a process that uses high-contrast patterns to break up the appearance of the body outline.

"The crabs are highly variable in colour and pattern and are often extremely difficult to see. We used image analysis simulating predator (bird and fish) vision to test how shore crabs camouflage themselves," said one of the researchers, Professor Martin Stevens.

Researchers also found rock pool individuals had significantly higher levels of disruption, and this seems an effective way to disguise the body's outline in the complex rock pool backgrounds were matching the colour of the environment is often not possible.

"In contrast, mudflat crabs closely matched the mud in terms of colour, brightness, and pattern but lacked high-contrast disruptive markings that might give them away in the uniform mudflat environment.

"Shore crabs are often assumed to be dull and green, but in fact, they can be extremely colourful and every individual can look completely different. Our study goes part of the way to explaining why shore crabs are so diverse," concluded Professor Stevens.