A recent study published in Conservation Physiology found that great white sharks become more active in the presence of humans taking part in caged shark dives.
While ecotourism such as cage-diving activities has helped spur conservation-minded attitudes among participants, the impact on the sharks being exposed to such activities had not been thoroughly studied. Great white-centric tours have increased in recent years in locations such as in Australia, South Africa, the USA, Mexico, and New Zealand.
According to the study, researchers tracked ten white sharks at South Australia’s Neptune Islands with devices for nine days, finding that the increased movement when sharks are interacting with cage-diving operators results in overall dynamic body acceleration, a proxy for activity, 61% higher compared to other times when sharks are present in the area.
Since body acceleration is considered a proxy of metabolic rate, interacting with cage-divers is likely to use a lot more energy than standard white shark behaviors.
“This suggests that the cage-diving industry has the potential to affect the energy budget of white sharks,” said Charlie Huveneers, associate professor at Flinders University and the study’s lead researcher. “However, the mere presence of the cage-diving operators in the general vicinity of the sharks was not sufficient to elicit such behavioral changes. These only occurred when white sharks were close to the cage-diving vessels.”
Commercial white shark cage-diving uses approved and regulated attractants to entice sharks within close proximity of the cages and provide good viewing opportunities for divers. However, in contrast to many other shark-related tourism activities, operators are not allowed to feed white sharks. The interaction with cage-diving tourists is, therefore, not rewarded by more food. This suggests that the increased energy expenditure from interacting with cage-diving operators might not be compensated by either bait or natural prey consumption.
“Spending time interacting with cage-diving operators might distract sharks from normal behaviors such as foraging on natural, energy-rich prey like pinnipeds,” Huveneers said.
