With all due respect to the serpents of the world, legs are an exceptionally desirable feature for any terrestrial-based life form looking to do things like jump, or walk. That is, unless you’re a Pacific leaping blenny, which manages to not only accomplish both feats sans, well, feet, but is a fish to boot.

UNSW researchers, Dr Terry Ord and Courtney Morgans, of the Evolution and Ecology Research Centre, studied the unique fish in their natural habitat on the tropical island of Guam. Specifically, they were looking to see what effect (if any) the odd creature’s camouflage had on staving off predation from more conventional, able-bodied land predators. Their study will be published in the journal Animal Behaviour.

“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,” says Dr Ord, of the UNSW School of Biological, Earth and Environmental Sciences.

The researchers’ first step was to compare the coloring of five different populations of the fish around the island to the rocks where they dwell, and found that in each instance the markings were virtually identical. To Dr. Ord and his team, that’s a clear indication that the blennies’ camouflage is intentional. To test its effectiveness, the researchers produced realistic plasticine of the animals.

“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,” says Dr 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.

“This means the fish are uniquely camouflaged to their rocky environments and this helps them avoid being eaten by land predators.”

The next step was to study the coloring of closely related species, some aquatic and some amphibious. There were indeed similarities, which suggests to scientists that the ancestors of present-day land-dwelling fish had developed habitat-specific camouflage before they ever made the jump to land.

“These species provide an evolutionary snapshot of each stage of the land invasion by fish,” says Dr Ord.

The Pacific leaping blenny, Alticus arnoldorum, is about four to eight centimetres long and leaps using a tail-twisting behaviour. It remains on land all its adult life but has to stay moist to be able to breathe through its gills and skin.

The researchers provided no indication as to whether sharks would ever develop similar abilities, or if it’s safe for humans to go anywhere near a shoreline. To see a video of the Pacific leaping blenny living up to its namesake, click here.