In his 2001: A Space Odyssey, Stanley Kubrick famously depicted the apes’ mastery of tools as the dawn of civilisation; a doorway to a command of technology that would shape society irrevocably. It’s very dramatic and very poetic… but it’s missing one thing. What if it were fish?

Scientists have debunked the belief that using tools is a practice unique to mammals (and birds, by the way) after documenting a succession of incidents in which tropical fish are seen smashing shellfish against rocks to open and eat the meat inside.

New research, led by Macquarie University in Sydney, Australia has now captured evidence of such tool use in no fewer than five species of wrasse fish across the western Atlantic, providing yet further proof that the cognitive abilities of fish have been vastly underestimated for years.

It’s all been published in the scientific journal, Coral Reefs; a groundbreaking study led by Dr Juliette Tariel-Adam from the School of Natural Sciences at Macquarie University, in which tool-use in multiple species of wrasse – a colourful reef fish – has been documented in such detail for the first time.

It logs fish deliberately picking up hard-shelled prey like crabs and molluscs and smashing them against hard surfaces like rocks to access the meal inside.

“Tool use is typically associated with humans, but this behaviour is proof that fish are far cleverer than they get credit for,” said Dr Tariel-Adam. 

The behaviour being displayed here is what is known as ‘anvil use’; the smashing of an object against a hard surface. This study – with contributions made from researchers across Australia, Brazil, and Caicos Islands – now provides the first evidence of such behaviour in several species of Halichoere wrasses, which suggests the behaviour is far more common than previously thought.

Wrasses use hard surfaces to crack open hard-shelled prey. Until now, this behaviour had been observed in a limited number of fish species all belonging to the same family of fish – wrasse.

Through a citizen science initiative, however, researchers gathered 16 new observations across five species of Halichoere wrasses. The findings mark the first evidence of tool use for three species and the first video evidence for the other two – extending the known range of anvil use to the western Atlantic, too.

“With these newly discovered tool-using species, it becomes clear that many species of wrasses use tools that we previously didn’t know about,” said Dr Tariel Adam.

“If we truly want to understand this behaviour , we need the help of divers, snorkelers, and marine enthusiast to report their observations. There are over 600 species of wrasses all around the world, and we are still far from knowing how many of them use tools. It’s only through collective efforts that we can uncover these hidden behaviours in marine life.”

The study also found that wrasses show flexibility in their tool use, selecting different types of anvils to crack open a vast diversity of prey, and may even switch anvils while attempting to open a single prey item.

“For a long time, tool use was thought to be exclusive to primates and birds,” said Professor Culum Brown, head of the Fish ab at Macquarie Universirty and senior author on the study.

“Our findings add to a growing body of research showing that fish are just as intelligent. They demonstrate flexible and dexterous tool use, expanding our understanding of tool use evolution in the animal kingdom.”

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