Many species, including crows, chimps, and capuchin monkeys, are known to use tools, but a new paper in Coral Reefs by A. M. Brown et al. (paper free at link and highlighted in Science NOW) reports what may be the first documented case of a tool-using fish.
On November 12, 2006, one of the authors (Gardner), diving off the Great Barrier Reef, observed a black spot tuskfish, Choerodon schoenleinii, holding a cockle in its mouth and repeatedly striking it against a rock until the shell broke. This was documented photographically below:
According to Science NOW, this is apparently not a one-off behavior:
The tuskfish caught on camera was clearly quite skilled at its task, “landing absolutely pinpoint blows” with the shell, Brown says. A scattering of crushed shells around its anvil rock suggests that Gardner didn’t just stumble upon the fish during its original eureka moment. In fact, numerous such shell middens are visible around the reef. Blackspot tuskfish, members of the wrasse family, are popular food fish, so it’s surprising that its shell-smashing behavior has remained unknown, Brown says. “My feeling is that when we go out and really look for it, it’ll turn out to be common.”
Now whether you see this as “tool using” of course depends on your definition of “tools.” Italian primatologist Elisabetta Visalberghi says that this is not tool-using because her definition “requires the animal to hold or carry the tool itself,” and this fish didn’t carry the rock. In fact, that kind of tool use would be impossible for most marine species, however smart (cephalopods are an exception). But it is tool use according to the definition of Jane Goodall quoted by the authors: “the use of an external object as a functional extension of mouth or hand in the attainment of an immediate goal.”
I’m not quite clear why animal behaviorists argue so strongly about what constitutes a tool. What seems more important to me is whether an animal has the cognitive and learning capacity to use things in its environment to fulfill its “desires.” Whether or not it carries things to do that seems to be a tangential issue.
Regardless, if this is a learned behavior (and I suspect it is), then it says something new about the intelligence of fish.
Jones, A. M., C. Brown and S. Gardner. 2011 Tool use in the tuskfish, Choerodon schoenleinii. Coral Reefs: DOI 10.1007/s00338-011-0790-y