Scientists from Florida, Japan and Hawaii have used tracking technology to find more out about the way the Tiger shark, Galeocerdo cuvier, hunts.
The Tiger sharks, from the west coast of Hawaii Island, were fitted with high resolution accelerometers – a technology that records speed, depth, temperature and acceleration – and digital cameras to record exactly what the sharks do as they travel across their large home ranges.
The scientists from the University of Hawaii’s Institute of Marine Biology (HIMB), the University of Tokyo’s National Institute of Polar Research and the University of Florida found that sharks yo-yo up and down the water column continually beating their tails and rarely gliding.
Initially this ‘yo-yo diving’ behaviour, which is also seen in many other sharks and open water fish species, was assumed to be for energy conservation, hunting or navigation. This study has revealed that it is actually a search strategy that effectively combs large three-dimensional spaces for prey.
Camera images revealed that the sharks frequently encountered a variety of potential prey fish with the camera of a single shark capturing over 150 images of prey alone. Sharks were also observed accelerating from seabed to follow a school of fish for over 20 minutes and there were frequent bursts of swimming to pursue other reef fish.
Dr Carl Meyer the lead US scientist from HIMB said: "These findings are exciting because they have given us unprecedented new insights into the behaviour of these huge and difficult to study marine predators.
"Although we have long debated the reasons for the yo-yo diving, we have only recently developed tools allowing us to directly measure the behaviour in sufficient detail to understand what these animals are actually doing”.
Tiger sharks are cosmopolitan predators which consume a wide variety of prey, and have large home ranges, moving hundreds of kilometres between oceanic islands and far out into open ocean to fill their resource needs.
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