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Aug 20

Animal Record Holders: Smartest Invertebrate

In 2008, staff at the Sea Star Aquarium in Coburg, Germany, were faced with a puzzling enigma. A lamp in the aquarium kept mysteriously going off, shorting the electricity supply in the entire building and threatening the lives of the other animals when water pumps stopped working. It took the staff three nights, sleeping on the floor of the aquarium, to discover the cause of the blackouts. The culprit was a naughty little octopus called Otto.

Otto had already been causing problems. Not only did he occasionally juggle a few of his fellow tank mates around with his many arms – including some distressed hermit crabs – but he also threw stones against the side of his tank, damaging it. Now, it seemed, Otto had become annoyed by the bright light shining into his aquarium from the lamp above, so he learned how to swing himself onto the rim of his tank and squirt a carefully-aimed jet of water onto the spot light, short-circuiting it. When the staff realised that Otto was responsible, they moved the light higher, but Otto – who seemed to suffer from octopus ADD – was still coming up with new stunts to get people’s attention and to cure his boredom.

But none of this is as surprising as you might think. The cephalopods – octopuses, squids and cuttlefish – are the most intelligent of all non-backboned animals, with the largest brain relative to body size and weight than any other invertebrate, fish, reptile or amphibian. They get bored very easily, especially in captive environments, are capable of learning and can solve complex problems.

Octopuses in particular like to play. They inspect toys that have been dropped into their tanks, puffing them around with jets of water. They watch over creatures and can mimic their movements and behaviours accurately. If kept in a tank enriched with natural features, they grow faster, learn faster and remember more than if they are just placed in a bare, empty tank. During one study, octopuses were taught to attack a specifically colour ball in order to get a reward of food. More octopuses in an adjoining tank were allowed to watch this and they learned which ball to attack in less time than it had taken the original octopuses to learn by trial and error.

800px-Octopus_marginatus

Photo: Nick Hobgood

So why are octopuses so smart? It’s probably partly because octopuses and other cephalopods, unlike most other molluscs (snails, slugs and clams etc), are active predators, which means they need brainpower to locate and capture their prey, and also partly because they have very dexterous arms. Their arms can open screw jaws, use stones to bash open shells and even pick up snapped-off jellyfish tentacles and wield them as weapons. Some ‘walk’ on the sea floor using two of their legs as if they were bipedal.

Oh, and finally, did I mention that octopuses like to escape? Sid the octopus, a resident of Dunedin Aquarium, New Zealand, escaped from his tank and spent a few days hiding out in a drain before being spotted by a staff member making a dash for the door. He was recaptured but later released into the wild. Sid’s tank mate, another octopus called Harry – after Houdini himself – also made a bid for freedom and was found halfway up a staircase. It’s not just their intelligence that makes them great escape artists; it’s also the fact that they can slip through tiny gaps little bigger than their own eyeballs, as the remarkable video below demonstrates.

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