If you've seen even a single shark documentary, then you've probably heard that the majority of attacks on humans are likely due to sharks mistaking people for seals. Scientists now say they've confirmed that theory, using computer models.
A large percentage of shark attacks involve great white sharks attacking surfers as they sit on or paddle their boards. In the past, studies have shown that when viewed from below, surfers on boards have a silhouette similar to that of pinnipeds (seals and sea lions) – these animals are among the great white's natural prey.
Led by post-doctoral researcher Dr. Laura Ryan, scientists at Australia's Macquarie University recently set out to explore this theory further.
Doing so involved using both stationary and travelling upward-facing cameras to shoot underwater video of subjects such as rectangular floats; pinnipeds swimming; humans swimming different strokes; and humans paddling on surfboards of various sizes. The footage was shot in a large tank at Sydney's Taronga Zoo. For the travelling shots, a GoPro was mounted on an underwater scooter that was moving at "a typical cruising speed for predatory sharks."
The footage was subsequently analyzed utilizing computer models based on existing shark neuroscience data, which simulated the manner in which a juvenile great white shark would process the shapes and movements of various objects. Juveniles are involved in a disproportionately large number of attacks, likely due to the fact that their vision is poorer than that of their adult counterparts.
The analysis reportedly confirmed that young great whites are indeed prone to mistaking humans on surfboards for pinnipeds, as the sharks likely perceive the two as looking very similar – this is particularly true of people on short boards. Changing the colors of the boards probably wouldn't help, as it is believed that sharks are mostly color blind. The scientists are looking into other preventative measures, however, such as adding high-intensity LEDs to the underside of boards, to break up their silhouette.
"Understanding why shark bites occur can help us find ways to prevent them, while keeping both humans and sharks safer," says Ryan.
The research is described in a paper that was recently published in the Journal of The Royal Society Interface.
Source: Macquarie University
