THE grey reef sharks in this shot seem to be just hanging in the water in a behaviour never reported before in these animals.
Working in an international team of researchers, Laurent Ballesta at Andromede Oceanology in France snapped this cohort of grey reef sharks (Carcharhinus amblyrhynchos) in the South Pacific Ocean. They were swimming against water currents, but barely moving their tails.
The research revealed that the sharks were floating using the upward movement from currents, effectively “surfing” and cutting their energy consumption by about 15 per cent (Journal of Animal Ecology, doi.org/gkdq).
More than 500 grey reef sharks live in the southern channel of Fakarava atoll, a coral reef in French Polynesia. The team studied them using tags, cameras and observations. Surfing the channel with minimum effort gives the sharks a break from the continuous swimming that provides them with oxygen.
During a diving trip, lead researcher Yannis Papastamatiou at Florida International University observed the sharks using a conveyor belt-like system to surf: the one at the front lets the current carry it to the back of the line and another shark takes its place.
The study reveals what Papastamatiou calls energy seascapes: spatial representations of the energy it costs an animal to move through a marine environment. It might explain, says the researchers, why large groups of sharks gather in certain areas of ocean.
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