Why cage-diving may lead to sharks going hungry: Concern over great whites using up so much energy interacting with divers that they don’t have enough left to hunt
- Study shows that white sharks are more active when interacting with divers
- Dynamic body acceleration is 61 per cent higher compared to other times
- Cage-diving is available in Australia, Africa, the U.S, Mexico and New Zealand
A new study showing that shark activity increases dramatically when they interact with cage-divers has raised questions over the impact of wildlife tourism.
The findings reveal that white shark activity soars when the predators are around cage-dive boats.
Conservationists fear that expenditure of energy may impede the sharks’ ability to hunt their natural prey.
A new study showing shark activity increases dramatically when they interact with cage-divers has raised questions over the impact of wildlife tourism
In recent decades, wildlife tourism has rapidly expanded and is one of the fastest growing sectors of the holiday industry.
Chances to cage-dive with predatory white sharks are available in Australia, South Africa, the United States, Mexico, and New Zealand – with up to seven companies operating simultaneously at one site.
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Previous studies have shown that wildlife tourism can change the behaviour of species by altering their habitats or eating patterns.
But how the changes affect the health of individual animals or animal populations was unclear.
The new study, published in the journal Conservation Physiology, shows that white sharks are more active and likely use more energy when interacting with tourism operators compared to when operators are absent, raising questions about behavioural changes such tourism may be causing.
Chances to cage-dive with predatory white sharks are available in Australia, South Africa, the United States, Mexico, and New Zealand – with up to seven companies operating simultaneously at one site
The researchers tracked 10 white sharks at South Australia’s Neptune Islands with devices for nine days.
They found that the increased movement when sharks are interacting with cage-diving operators results in overall dynamic body acceleration, a proxy for activity, 61 per cent higher compared to other times when sharks are present in the area.
The researchers said that 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 behaviour.
Lead researcher Dr Charlie Huveneers, Associate Professor at Flinders University in Australia, said: ‘This suggests that the cage-diving industry has the potential to affect the energy budget of white sharks.
‘However, the mere presence of the cage-diving operators in the general vicinity of the sharks was not sufficient to elicit such behavioural changes. These only occurred when white sharks were close to the cage-diving vessels.’
Dr Huveneers added: ‘Spending time interacting with cage-diving operators might distract sharks from normal behaviours such as foraging on natural, energy-rich prey like pinnipeds [seals].’
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.
The research team said this suggests that the increased energy expenditure from interacting with cage-diving operators might not be compensated by either bait or natural prey consumption.
They said their findings indicate that wildlife tourism may change the activity levels of white sharks, and called for an understanding of the frequency of shark-tourism interactions to appreciate the impact of ecotourism on the species’ fitness.
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