Focus-Science and Technology - - Zoology -

Tool use is a sign of higher in­tel­li­gence that var­i­ous fish have. Archer­fish use droplets of wa­ter as bul­lets to shoot in­sects off veg­e­ta­tion above the wa­ter’s sur­face; they can even ad­just the aim to com­pen­sate for the way light bends as it passes be­tween air and wa­ter, and still hit their tar­get.

A few years ago, re­searchers in Nor­way saw cap­tive At­lantic cod in­vent­ing a new tool to feed them­selves. Three cod, in two sep­a­rate tanks, ac­ci­den­tally got their iden­ti­fi­ca­tion tags tan­gled in a string that re­leased food from an au­to­matic feeder. Be­fore­hand, the cod had learned to pull the string with their mouths to get food. But these three cod worked out that it was much faster to de­lib­er­ately hook their tags on the string then spin around and gob­ble the food.

Dr Helen Scales is a ma­rine bi­ol­o­gist and sci­ence writer. Her lat­est book is Eye Of The Shoal (£16.99, Bloomsbury).

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