Tool Time For Tuskfish

As reported last week in ScienceNOW¹, a professional diver exploring the Great Barrier Reef off the coast of Australia recently snapped the first photos of a fish using tools. The diver, Scott Gardner, came across a blackspot tuskfish (Choerodon schoenleinii) that was hovering over a sandy area near a rock with a clam in its mouth. The tuskfish rolled on its side and, with a repeated cracking noise, slammed the clam against the rock until the shell fractured. Here’s one of the photos that Gardner took of the industrious (and hungry) tuskfish:

Tuskfish cracking open clam (photo credit: Scott Gardner)

While there have been anecdotal accounts of other fish using tools, this is the first time that this type of behavior has been caught on film.

What Is Tool Use, Anyhow?

In an interesting aside, this incident has brought to the forefront some of the ways in which it is difficult to define, and reach agreement upon, exactly what constitutes “tool use” in animals.  As noted in the ScienceNOW article, there has been previous debate over whether stingrays and archerfish targeting jets of water to capture prey constitutes tool use (is a solid external object necessary for there to be a tool?), as well as whether tool use “requires the animal to hold or carry the tool itself, in this case the rock.”

The research paper regarding this tuskfish behavior, which was published in the most recent issue of Coral Reefs², the official Journal of the International Society for Reef Studies, argues that the tuskfish using the rock as an anvil to open the clam conforms to a definition of tool use first formulated by Jane Goodall back in 1970, that tool use is “the use of an external object as a functional extension of mouth or hand in the attainment of an immediate goal.” The paper adds: “The use of a rock as an anvil rather than a hammer could be considered a sign of intelligence considering the ineffectiveness of manipulating a freely suspended tool in water. The images certainly provide an interesting starting point for further comparative studies on tool use in fishes.”

The ScienceNOW article describes how Culum Brown, a behavioral ecologist at Macquarie University in Sydney, Australia, and a co-author of the Coral Reefs paper:

argues that it’s not logical to apply the same rules to fish as to primates or birds. For one thing, fish don’t have anything but their mouths to manipulate tools with, and for another, 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.’

Those of you who pay close attention may already have noted that the definition of tool use can stir controversy. For example, beginning at the 10:34 mark in her video presentation relating to the awesome octopus, Maggie Koerth-Baker describes two very divergent definitions that might lead to different conclusions about whether the octopus engages in tool use: (a) a stricter definition that requires that an animal use a solid object to solve an “immediate problem,” rather than just to provide defense, and (b) a broader definition holding that tool use occurs whenever an animal modifies an object so as to alter some aspect of its environment.

Food For Thought

In considering tool use by animals, here are some things you might want to ponder:

• Which of the above definitions makes the most sense to you?
• Does it matter whether the behavior is performed by a captive animal (like the New Caledonian crow) or in the wild?
• Are definitions of tool use inherently anthropocentric and subjective? That is, are we trying to come up with a definition that basically requires the behavior to look like something a human would do (if it really is a tool, then I should be able to see the Craftsman logo) before we accept it?
• Is it significant whether the behavior is widespread? That is, if the behavior is only observed once or twice, is it a fluke? If the behavior is widespread, is it mere instinct?
• Is nest building by birds an example of tool use?

Conclusion

There will undoubtedly be more AnimalWise posts about tool use. In the meantime, if you run across any tuskfish, you should look very closely to see if you can see their very small, teeny-tiny tool belts. They really are quite cute.

Here are some more photos (note, the following pictures may not be suitable for small children and clams):

More Scenes from "Crouching Tuskfish, Hidden Clam" (photo credit: Scott Gardner)

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¹ScienceNOW, “Diver Snaps First Photo of Fish Using Tools,” July 8, 2011.

²Jones, A.M., Brown, C., Gardner, S. Tool use in the tuskfish Choerodon schoenleinii? Coral Reefs. DOI:10.1007/s00338-011-0790-y.