Smart Fish

By sunup, the orange dotted tuskfish has already arrived at his workshop on Australia’s Great Barrier Reef, and to get ahead in this challenging world it has opted for ingenuity. It has joined the exclusive club of animals – predominantly mammals and birds – that have found ways of using ‘tools’. It likes to eat clams, so it uses a neat trick to expose one buried in the sand. Instead of blowing a mouthful of water at it, the fish turns away from the clam and snaps shut its gill covers, blasting water in the same way that closing a book creates a waft of air. Then it grabs the clam in its mouth and, with a deft movement of the head and body, smashes it against a coral. The blows are so precise that, after a short time, the shell breaks apart. The fish then gobbles it down, swallowing the soft flesh and spitting out shattered shell fragments.

While scouring the reef for signs of tuskfish activity, one individual in particular caught the eye of assistant producer Rachel Butler and underwater cameraman Roger Munns.

‘We weren’t really sure we were going to see anything when we first found the tuskfish we nicknamed “Percy”, but within a few minutes he’d found a shell and set off to his favourite coral head, where he proceeded, with violent swings of his head, to smash it to bits. Although we knew what to expect, Rachel and I were both dumbfounded at his amazing behaviour.’

Diver and fish
Blue Planet II

Seeing a fish use a "tool" for the first time was truly remarkable

‘Seeing a fish use a “tool” for the first time was truly remarkable,’ adds Rachel. ‘Percy came back to his “castle” each day. He was a tenacious little thing, swimming for hours every day in search of clams that he would bash on his anvil for up to 20 minutes at a time.’

Tuskfish and shell

Piles of broken shells scattered around the coral head indicate that the tuskfish regularly uses the same ‘anvil’. Furthermore, similar collections of broken shells can be observed across the Great Barrier Reef, suggesting the behaviour may be widespread. Despite being a relatively conspicuous behaviour, anvil use in tuskfish had rarely been observed in Australia prior to commencement of filming Blue Planet II and has been professionally filmed for the first time by this series.

These resourceful tuskfish are in the wrasse family, and since these observations were reported several others have come to light. Off the Florida coast, the yellow-headed wrasse smashes scallops against an anvil rock, and in the Red Sea three species of wrasse collect sea urchins, drag them back to their territory, and break off the spines and split the test against a chosen rock to get at the soft parts inside. Fish are not noted generally for their intelligence, but digging up a clam or collecting a sea urchin, carrying it some distance in its mouth to a preferred anvil and then smashing it open, like a sea otter, requires some degree of forward thinking, and for a fish that’s a big deal.

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