May 24 (UPI) -- Crab species seem to exist in habitats that help them easily disguise their bodies, a new study says.
Researchers at the University of Exeter contrasted the color patterns of shore crabs from the mudflats with those living in rock pools in a study published Friday in Scientific Reports. They collected the shore crabs from six sites in Cornwall, England.
"The crabs are highly variable in color and pattern and are often extremely difficult to see," study author Martin Stevens said in a news release. "We used image analysis simulating predator (bird and fish) vision to test how shore crabs camouflage themselves."
The researchers captured images 47 images of crabs from the rock pool and mudflats. The rock pool habitat was made up of large rock clusters that formed deep gullies containing small pebbles and sand. In contrast, the mudflats habitat contained large areas of dark brown mud and surface algae, with rocks and other objects lying around it.
The look of the mudflat crabs closely resembled the mud they lived in, compared to the appearance of the rockpool crab, which blurred out its body outline by blending with the highly contrasting color design of its background. That concept is known as "disruptive coloration."
Unlike past work that analyzed background matching and disruptive camouflaging using artificial systems, this study examines the camouflage habitats real animals use, the researchers say.
"Shore crabs are often assumed to be dull and green, but in fact they can be extremely colorful and every individual can look completely different," Stevens said. "Our study goes part of the way to explaining why shore crabs are so diverse."