Pacific leaping blennies, legless terrestrial fish, use camouflage to avoid predation by birds, lizards and crabs, according to a University of New South Wales (UNSW) study.

For the study, UNSW researchers, Dr Terry Ord and Courtney Morgans, of the Evolution and Ecology Research Centre, studied the world's strangest animal in its natural habitat on the tropical island of Guam.

"This terrestrial fish spends all of its adult life living on the rocks in the splash zone, hopping around defending its territory, feeding and courting mates. They offer a unique opportunity to discover in a living animal how the transition from water to the land has taken place," Ord, of the UNSW School of Biological, Earth and Environmental Sciences, said in a statement.

The researchers first compared the color of five different populations of the fish around the island to the rocks they lived on.

"They were virtually identical in each case. The fish's body colour is camouflaged to match the rocks, presumably so they aren't obvious to predators," says Dr Ord.

In order to verify whether camouflage indeed helped to reduce predation, the researchers created models of blennies out of plasticine.

"We put lots of these model blennies on the rocks where the fish live, as well as on an adjacent beach where their body colour against the sand made them much more conspicuous to predators," said Ord. "After several days we collected the models and recorded how often birds, lizards and crabs had attacked them from the marks in the plasticine. We found the models on the sand were attacked far more frequently than those on the rocks."

And to find out the evolution of this unique fish, researchers studied its related species of fish (both aquatic and amphibious). They found that the species shared the same color, and the ancestors of the land-dwelling fish already had a colouration that matched the rocky shoreline before they moved out of the water.

Alticus arnoldorum, the other name for blenny, measures four to eight centimeters long and leaps using a tail-twisting behavior. Although, it pretty much stays on land, the fish has to stay moist to facilitate breathing through its gills and skin.

The study will be published in the journal Animal Behaviour.