Retrieving an out-of-reach object by pulling a string attached to it.
During a cold Swedish winter, a raven watches a fisherman cut a small hole in a frozen lake. He drops in a baited fishing line attached to a stick to secure it over the hole. After he leaves, the raven flies down and examines the situation. Although she cannot see deep down the dark waters, she takes the line in her beak, pulls it, and steps on the loop. Repeating this sequence several times, she eventually reaches the end and eats the bait. Other ravens observe how she got her easy catch and make their own attempts with the numerous ice-fishing holes in the country’s largest lake. By the end of the winter, local fishermen have stopped ice fishing because they nearly always return home empty-handed due to the ravens’ efficient pilfering (Larsson 1958).
These ravens exhibited spontaneous string pulling: they retrieved out-of-reach food (bait and fish) by pulling a string (fishing line) attached...
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