Great white sharks don’t mistake surfers for seals when they approach from below, grab and bite them, according to a new study by shark behaviourists – theyâre simply trying to work out with their mouths what the human and the board are.
This might not bring much comfort to the surfers, or to all the divers who just know that being above great whites at the surface is not the best idea.
However, the study does suggest that because the sharks realise the difference, a bite on a human is likely to be lighter than it would have been on a seal it plans to eat.
According to Dr Erich Ritter of the University of West Florida and Alexandra Quester from the University of Vienna, who have together just published a paper in the Journal of Marine Biology, the “mistaken identity theory” is the most common assumption and is itself mistaken.
The researchers evaluated almost 70 incidents that occurred on the USA’s West Coast between 1966 and 2015, focusing primarily on the length of the shark and the level of damage done.
If the attacks were down to mistaken identity, they reckoned that the length of the sharks attacking the pinnipeds (seals or sea-lions) would be identical to that of those sharks that bit surfers, and that the wound severity would also be identical between the pinnipeds and the surfers (boards and bodies).
This is because great whites need to be skilled to catch agile pinnipeds, and it is only mature sharks (at least 4m long) that tend to succeed, using a massive initial bite to prevent their prey escaping. The sharks that bit the surfers tended to be much smaller than 4m, and their bites were usually too superficial to incapacitate a pinniped.
Should more than one bite occur, say Ritter and Quester, the motivation may still be exploration but could also reflect target practice, play or a follow-up prompted by the surfer’s initial reaction.
Read “Do White Shark Bites on Surfers Reflect their Attack Strategies on Pinnipeds?“ here
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07-Dec-16
