A snorkeler in Boca Raton learned the hard way over the weekend one of the reasons why nurse sharks are so unique.
On Sunday, Shaylen Borkowski, 23, was bitten by a small nurse shark that refused to let go of her arm even after being taken out of the water.
Nurse sharks are unusual in that they are suctorial feeders, meaning they suck their prey into their mouth as they use their teeth to cut and grind. Nurse sharks have a central ridge in their mouth that helps pull food in while their teeth act as cheese graters on either side.
The suctorial function also allows them to lay motionless on the sea floor because they can pull in water and push it over their gills.
Most sharks have to keep moving to keep water rushing through their gills.
George Burgess, director of the International Shark Attack File at the University of Florida, said the suctorial feeding is an evolutionary strength.
“It’s also a defensive mechanism in that if something is going to try to bite you and you grab on and hold on long enough you may be able to wait out the predator,” Burgess said.
But it more of a weakness when dealing with dealing with humans.
Because nurse sharks can remain motionless, people try to pet them or grab them, he said.
“It’s instinctual, but has a serious downside because it wasn’t developed in the presence of humans,” Burgess said. “They are slow swimmers and kind of saunter around but if the animal gets pissed off enough it grabs and doesn’t let go.”
Alex Smoake was with the woman, whom he declined to name but was identified by Miami television station WTVJ as Shaylen Borkowski, and two other friends at Red Reef Park when the encounter took place. Smoake said the friends were snorkeling for the first time.
“There was a bunch of little kids around the reef poking around looking under the rocks,” Smoake said. “One of the sharks got frightened and (swam) out. When it turned directions, my female friend was in the way and it latched onto her arm.”
Beachgoers said they saw at least one person antagonizing the shark by holding its tail, according to news reports.
The shark was killed before the woman was taken to the hospital with the shark still attached.
Smoake said he and his friends were not in that group.
Stephen Kajiura, a shark researcher for Florida Atlantic University, said adult nurse sharks have larger mouths and can more easily detach from their prey if they want.
But because the babies have small mouths it’s harder for them to stop the suctorial function and once they are taken out of the water, the gills slits can collapse making the suction attachment even stronger.
“Poor shark, it should never have been bothered in the first place,” Kajiura said.
Palm Beach Post staff writer Jorge Milian contributed to this story.