SHARKS may be even more calculating than they seem. They can learn cognitive skills from other sharks and recent experiments reveal they have a grasp of quantity.
Vera Schluessel at the University of Bonn in Germany and her colleagues tested how well 12 bamboo sharks could recognise different numbers of objects.
Each shark was put in a training pool with pictures of two different groups of geometric shapes projected onto a wall. The team then cycled through at least 40 objects of different shapes and shades to ensure the sharks weren鈥檛 simply picking up on the darkness of the objects or the area of wall they covered.
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Around half the sharks learned to reliably press their nose against the image with the most objects, after which they were rewarded with food. These sharks only seemed capable of picking out the bigger group if it contained at least two more objects than the smaller one. This may be because the difference between six and seven fish or predators is unimportant in the wild, says Schluessel.
The reason not all the sharks learned how to do the task could be because they, like all animals, have intellectual differences.
Sharks join a growing number of animals that have been discovered to have similar skills at distinguishing quantities, including black bears, guppies and rhesus monkeys. In one experiment, dogs and wolves were able to reliably pick the larger of two groups. But dogs could only do so when one of the groups had substantially more objects.
Social sharks
Some shark species are social learners and can perform a task in a tank more quickly if they watch another shark that has already been trained to do it.
This contradicts the image of sharks as mindless, solitary creatures. Just like humans, sharks learn from their own experiences and failures. And just as we do, sharks can learn from each other鈥檚 experiences too, says Catarina Vila Pouca at Macquarie University in Australia.
Being able to learn from others is enormously beneficial. Not only does it save time, but watching another shark鈥檚 success at feeding or failure to escape predators could be a matter of life or death.
Schluessel and her colleagues have also previously found that bamboo sharks have a sophisticated ability to discern categories, such as snails or fish, enabling them to get a treat even if pictures look remarkably similar.
This resembles our ability to look at a goldfish and a salmon and know that they are the same type of thing, even though one is 30 times the size of the other.
The team is currently writing up the findings for publication.
