(Tool-using orange-dotted tuckfish; Video still: UC Santa Cruz)
Fish are adept at using rocks as tools, and a researcher has the video to prove it. The footage, shot in Palau and described in the journal Coral Reefs, is the first ever to show a fish using a tool.
In the video, an orange-dotted tuskfish is seen digging a clam out of the sand. The tuskfish then carries the clam over to a rock and repeatedly throws the clam against the rock to crush it. This is basic tool tech, but it does the job and is impressive when you consider that fish don't have hands or much to work with in their habitats.
Giacomo Bernardi, a professor of ecology and evolutionary biology at the University of California, Santa Cruz, shot the video.
(Bernardi; Image: UC Santa Cruz)
"What the movie shows is very interesting," Bernardi was quoted as saying in a press release. "The animal excavates sand to get the shell out, then swims for a long time to find an appropriate area where it can crack the shell. It requires a lot of forward thinking, because there are a number of steps involved. For a fish, it's a pretty big deal."
Tool use by fish may be much more common than previously realized. Since the early 1990s, various instances have been documented. All appear to involve a species of wrasse using a rock as an anvil to crush shellfish.
Just a few months ago, the first photographs of a fish using a tool were released. They showed a blackspot tuskfish. The phenomenom has also been spotted among yellowhead wrasse and sixbar wrasse.
"Wrasses are very inquisitive animals," Bernardi said. "They are all carnivorous, and they are very sensitive to smell and vision."
It's not as though all wrasses are close family members either. The observed tool-using species cover a broad range of evolutionary history.
"They are at opposite ends of the phylogenetic tree," Bernardi explained, "so this may be a deep-seated behavioral trait in all wrasses."
It wasn't that long ago that tool use was considered to be an exclusively human trait. I can remember watching Jane Goodall on TV back in the day showing tool use among chimpanzees. At the time, that was a stunning revelation. Since then, numerous other animals have been observed using tools, including various primates, dolphins, elephants and birds. Rooks are particularly well-known for their tool skills, as you can see in this video.
Bernardi, who studies fish genetics, said there may be other examples of tool use in fish that have not yet been observed. "We don't spend that much time underwater observing fishes. It may be that all wrasses do this. It happens really quickly, so it would be easy to miss."