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San Diego, CA - Lemon sharks have the ability to learn from each other's behaviour, US scientists have found. The team compared the performance of inexperienced juvenile sharks working with both trained and untrained partners.
The results showed that sharks working with trained partners could complete tasks more quickly and successfully. The study is thought to be the first to demonstrate social learning in any cartilaginous fish.
"I think it's a really cool finding," said lead author Dr Tristan Guttridge from the University of Miami, Florida whose paper was published in the Journal of Animal Cognition.
The results are a significant breakthrough, according to Dr Guttridge, director of the Bimini Biological Field Station Foundation in the Bahamas.
"It's a pretty exciting finding that these little lemon sharks are able to pick up social cues from each other," he said. The evidence came from a task-based experiment with juvenile sharks conducted in an underwater pen.
The pen contained an "indicator zone" which functioned as the start area. In the other corner was a "target zone" in which there was a black and white marker that could be covered or exposed by the scientists. When the sharks swam into the indicator zone, the target was exposed.
By swimming into the target zone and bumping the black and white target they earned a piece of barracuda, which was lowered into the pool. One group of sharks, the "trained demonstrators" was trained in this task until they could complete it roughly six times every minute. Another group, the "sham demonstrators", was left untrained.
Members of each group were then paired up with "naive", untrained sharks and the pairs were introduced to the pool, observed and filmed.
"You can see the shark that's been with the demonstrator, how interested he is in the particular zones, moving between them," said Dr Guttridge of the video footage.
"It's really quite obvious that they're picking up social cues from the other individual and the excited behaviour of the demonstrator is getting the other guy interested as well."
The study then isolated those sharks that had observed the demonstrators to see how they performed on their own.
The juveniles that had been paired with "demonstrator sharks" completed a greater number of trials more quickly than those with untrained partners.
Dr Guttridge originally thought of the experiment while watching the behaviour of lemon sharks near his research station.
"If you see one performing these kind of tight circles and these excited foraging behaviours, often very quickly another one will start doing the same thing."
The findings for lemon sharks suggest that other species of cartilaginous fish may share this ability "[They are] attracted to the kind of behaviour of the other individual and so the lemon shark was the perfect model species for this."
Social learning has already been widely demonstrasted among other species and animal groups including corvids, chimps and bats.
"In all these other animals it has been shown to be of real importance to different behavioural processes," said Dr Guttridge, suggesting the same could be true for sharks.
"Sharks do migrate long distances and maybe there's a social context to this as well," he told BBC Nature, comparing his subjects with whales and dolphins that learn their migration routes through culture.
The biologist now hopes to better understand the processes that lemon sharks use to learn from each other.
"There are many different social learning processes and in this paper we haven't demonstrated one over another," he said.
"We would need to do a much more controlled experiment to eke out the actual social learning processes that are going on."