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A bull shark swims through a school of fish.
- In the past month, three young people have been attacked by sharks in North Carolina.
- The spate of attacks likely involved two different shark species.
- Shark experts said that because the waters along the East Coast are warming due to climate change, some shark species' ranges are expanding.
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On Sunday, an 8-year-old boy was attacked by a shark in the waters near South Beach, North Carolina. He escaped with a bite on his leg. Less than a week prior, 19-year-old Austin Reed suffered what he described as a "deep tooth bite" on his foot while surfing near Ocean Isle Beach, North Carolina.
But these attacks paled in comparison to the June 2 attack on 17-year-old Paige Winters, who lost most of her left leg and two fingers during an encounter with a shark at North Carolina's Atlantic beach. Winters' father rescued her from under the water after punching the shark in the nose five times.
Read More: An 8-year-old boy is believed to be the third shark attack victim in North Carolina this month
That's more unprovoked shark attacks in North Carolina already this month than swimmers experienced during the entirety of 2018, according to the International Shark Attack File database.
But Gavin Naylor, director of the Florida Program for Shark Research (which runs that database), told Business Insider it's difficult to connect the three attacks as a trend, since two different shark species were likely involved.
"People tend to conflate all shark bites as the same kind," Naylor said.
But according to Naylor, the lower limb bites likely came from a black-tipped shark - a smaller, less aggressive species - whereas Winters probably encountered a bull shark.
However, George Burgess, who led the Florida Program before Naylor, told Business Insider that there is a trend that could connect these attacks: climate change. As ocean waters get warmer, they become more hospitable to larger and more diverse shark populations. And that could mean more attacks.
"Water temperatures have risen along east coast of US, and with that comes animals that like warmer water, including sharks," Burgess said.
Warmer waters mean more sharks
Oceans absorb 93% of the excess heat trapped on the planet by greenhouse gases; last year was the hottest on record for the world's oceans. That impacts the range of marine animals like sharks, which rely on the water temperature to regulate their body heat.
"Global climate change has prompted warmer water temperatures farther northward," Burgess said. That means more fin sightings in places historically considered shark-free.
A 2018 study published in the journal Scientific Reports noted that between 2011 and 2016, bull sharks moved their nurseries farther north, into North Carolina waters. The study authors found that the bull shark presence near the Pamlico Sound was correlated with water temperature: When temperatures in Pamlico Sound dropped below 22 degrees Celsius, no juvenile bull sharks were observed in the area.
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The bull shark, Carcharhinus leucas, can be dangerous to humans. It often stays in the shallow water near the shore and in the estuaries of rivers.
Two types of shark attacks, three survivors
But just because the three North Carolina attacks happened in rapid succession doesn't mean they're related.
Black-tipped sharks - which were likely responsible for the attacks on Reed and the young boy - "are as shocked at biting people as people are at being bitten," Naylor said. "There are no recorded fatalities from black-tipped sharks."
These smaller sharks are generally involved in "hit-and-run attacks," in which the animal bites the lower leg and swims away, Burgess said.
That type of single chomp is an "exploratory bite," according to Erich Ritter, a scientist from the Shark Research Institute at Princeton University.
"The shark is trying to figure out what we could be," he said. "The animal's not clamping down because we're an unknown and could be dangerous."
A black-tipped shark (Carcharhinus limbatus) swims in the waters of Walkers Cay in the Bahamas.
But Burgess, Ritter, and Naylor all think a bull shark attacked Winters. These animals can weigh up to 500 pounds and reach lengths of 11.5 feet.
"Bull sharks are animals that want to continue their attack after the first bite and don't give up," Burgess said. "Not all sharks are that way."
Naylor said Winters' father was smart to intervene during his daughter's attack.
"It was exactly the right thing to do, he likely saved her life by upending the animal," he said.
North Carolina is a shark oasis
In 2018, Florida recorded 13 more shark attacks than North Carolina. But according to Burgess, North Carolina "is a great place to be a bull shark" because lots of rivers enter the Atlantic there.
"Bull sharks like brackish water and are known to even ascend into freshwater rivers that are farther inland to hunt," he said.
These river deltas, where fresh and salt water mix, are also prime fish habitats for fish - another factor that draws sharks closer to shore.
"Bull sharks ... pursue a variety of prey and interesting objects, which occasionally include people," Naylor said. "They're large animals, and quite tenacious."
Jo Yong hak/ Reuters
In the summer, bull sharks, tiger sharks, and black-tipped sharks all follow and feed on schools of fish near shore, Naylor added.
"If people are playing in the same waters, sharks will encounter the people, mistakes happen and someone gets bitten," he said. "If you see schooling fish, you'd be well advised to get out of the water."
With more people and more sharks in the water, interaction is more likely
Burgess said another factor in the higher number of shark attacks is simply that North Carolina's tourism industry has attracted more visitors to the state's beaches than in years past.
The number of shark attacks in a given year or region depends on how many people enter the water there. As the human population grows - the United Nations expects there to be 11.2 billion on Earth by 2100 - the frequency of shark attacks is expected to rise, too.
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"The thing is that there is just more people now than there were 50 years ago," Burgess said. "That's the underlying theme of shark attacks - over time, the people involved in aquatic recreation has gone up."