(Image source: Daily Mail)

BY STEVEN SPARKMAN

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Tool use is one of science’s sure signs of intelligence. Humans obviously use tools, as do other primates, elephants, crows, octopuses -- and now fish?

A writer for Wired UK explains:

“Professional diver Scott Gardner has captured what are believed to be the first images of a wild fish using a tool. The picture ... shows a foot-long blackspot tuskfish smashing a clam on a rock until it cracks open, so the fish can gobble up the bivalve inside.”

And the diver noted -- he didn’t catch the tuskfish just learning this trick.

He said the fish was a shell-smashing pro. The evidence -- its precision strikes and the small pile of shells around the rock. (Image source: Daily Mail)

In a new paper in the journal Coral Reefs, the authors claim this meets the definition of tool use first laid out by Jane Goodall in her work with chimps --

“The use of an external object as a functional extension of mouth or hand in the attainment of an immediate goal.” (Source: Coral Reef)

But not everyone agrees on this definition or whether this fish qualified as using tools. A writer for io9 notes:

“There's potentially a slight hitch with calling this tool use, though. As you might have noticed, the fish never actually touches the tool in question, which is the rock. Since the fish only ever handles the clam, can it really be said to be using a tool?”

For another example of a grey area in the subject, archer fish essentially use water as an extension of their body, knocking prey off branches overhead. If the tuskfish can be called a tool user, why not an archer fish? (Video source: Animal Planet)

Seagulls, too, have been known to drop nuts on rocks to crack their shells. But a primatologist tells ScienceNOW -- this behavior just doesn’t make the cut.

“The form of tool use described [in tuskfish] is cognitively little demanding and present in a variety of species. Often it has been labeled as proto-tool use because the object used to open the shell is still, fixated to the sea bottom, and not portable as stone tools used to crack open nuts by chimpanzees or capuchin monkeys are...”

But Dr. Culum Brown, one of the paper’s authors, defends the little tuskfish. He says if you define tool use in a way that only works for primates, then of course only primates will meet the definition.

The Daily Mail quotes him:

“As fish don't have any limbs to hold an object, Dr Brown hopes this definition can be loosened so that their own form of tool use can be recognised. … 'You cannot swing a hammer effectively underwater.'"

Until the behavior is documented in a little more detail, scientists won’t know whether the fish truly understands tool use. It’s thought process could be simply -- clam beats fish, rock beats clam, so fish beats rock.

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