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A fishy new tool user?

When Jane Goodall described chimpanzees using tools in the wild in 1960, it was the first scientific report of tool use in nonhuman animals. Since then, a select few other species have joined the list of animal handymen: mostly primates and corvid birds, but also dolphins, elephants, and octopuses.

Now, a paper published in the June 24 issue of Coral Reefs purports to present the first ever photographs of a wild fish using a tool. The images were taken by professional diver Scott Gardner while exploring Australia's Great Barrier Reef. They show a foot-long black spot tuskfish (Choerodon schoenleinii) holding a clam in its mouth, rolling onto its side, and hitting the clam against a rock. When the shell gave way, the fish ate the fleshy innards, spat out the shell fragments, and swam away.

Whether or not this qualifies as tool use is open to debate. The strictest definition of tool use requires that the animal hold or carry the tool itself. According to this definition, the behavior documented by Gardner would be described as proto-tool use, because the object used as a tool is fixed to the sea bottom. This form of tool use is present in a variety of species (such as seagulls that drop shellfish onto hard surfaces to crack them) and not as cognitively demanding as the true tool use shown by primates.

Culum Brown, a behavioral ecologist at Macquarie University in Sydney, Australia and a coauthor of the present paper, acknowledges this controversy. However, he believes that the rules of tool use cannot be the same for fish and primates for two major reasons.

One, fish don't have limbs to manipulate tools, so they must use their mouths. And two, water poses different physical limitations than air. "One of the problems with the definition of tool use as it currently stands is it's totally written for primates," he says. "You cannot swing a hammer effectively underwater." 

What do you think? Do we need a new definition for tool use to incorporate the challenges that using a tool underwater can pose?

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