Man-eating tiger sharks aren’t loners after all and can hunt in packs – making them even deadlier than previously feared, according to new research.
The terrifying predators pick and choose social groups – contrary to popular belief, say scientists.
But the friendships break down when they are exposed to bait provided by dive touring companies.
Study lead author Dr David Jacoby, a zoologist at Lancaster University, said: “The boundary between wildlife and people is becoming increasingly thin.
“So as well as observing a new social behaviour for the first time in what was once thought of as a solitary shark, we also measured the impacts of human activity on these predators’ interactions.”
The blunt nosed tiger shark is second only to the great white for the number of recorded attacks on humans. It has razor sharp, serrated teeth and powerful jaws that can snap a human in two.
They allow the ocean monster to crack the shells of sea turtles and clams.
Ten years ago an Australian holidaymaker was torn apart by a shoal off the coast of Queensland. The horrifying case was considered unusual because of their reputation as loners.
Now they have been observed enjoying each other’s company off Tiger Beach in the Bahamas – a popular resort.
The study in Frontiers in Marine Science is the first to show how bait feeding affects behaviour.
Interactions became more random when food was provided. They also exhibited a ‘take it or leave it’ attitude – suggesting it was not long-lasting.
If the frequency of tourism activity does not increase, sharks could likely retain natural behaviours when not being fed – and avoid dependence.
Dr Jacoby said: “Luckily, they seem to show some resilience to the bait feeding.”
Baited shark dives – carried out around the world to attract the animals for tourists – are controversial. Conservationists say they could make them less efficient hunters. Most species are facing extinction.
An international team combined acoustic tracking data with social network analysis to observe the tiger sharks over three years.
The waters investigated host a high proportion of females, especially during winter months, about a quarter of which are pregnant.
Senior author Professor Neil Hammerschlag, of the University of Miami, said: “Given tiger sharks spend months at a time out in the open ocean as solitary predators, it is amazing to me that they show social preferences when they aggregate in the Tiger Beach area.
“For nearly two decades, I have spent countless hours diving at Tiger Beach always wondering if these apex predators interacted socially. Now we know.”
Analysing the social behaviour of predators is vital. It builds a picture of how they live, what drives them to form social groups and the roles they play within the wider ecosystem.
Most shark species are facing extinction owing to verfishing and climate change.
Dr Jacoby added: “We hope if the frequency of these dive trips doesn’t increase, the sharks may be able to retain their natural behaviours regardless of their time spent near tourists during dives.”
In August 2011 a swimmer was killed in a tiger shark feeding frenzy as he went to retrieve a small boat that had broken free from its anchor. It was speculated they were younger sharks – as they were in a group. The builder was taking a break at the paradise Fantome Island with friends when the tragedy happened.
Tiger sharks can reach 17 feet in length. They are named after the dark stripes down their body, which fade as they get older.
The stomach contents of captured tiger sharks have included stingrays, sea snakes, seals, birds, squids, and even license plates and old tires.
The World Conservation Union (IUCN) lists the tiger shark as ‘near threatened’ throughout its range.
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