Researchers use DNA to ID shark tooth taken from boy's leg

A tooth taken from the leg of a boy bitten at New York's Fire Island National Seashore has been identified as that of a sand tiger shark, after a DNA comparison, researchers announced Wednesday.

University of Florida researchers compared DNA from the tooth to a genetic dataset of sharks to determine its species. Gavin Naylor, director of the Florida Program for Shark Research at the Florida Museum of Natural History in Gainesville, said it's the first time a shark involved in a bite has been identified using DNA.

Beaches were closed at Fire Island in mid-July after the 13-year-old boy and a 12-year-old girl were bitten. Both children were treated and released from a hospital. The girl reported seeing an orange-brown fish 3 feet to 4 feet long with a dorsal fin.

Lindsay French, program manager for the shark research center, arranged for the tooth to be sent to the researchers for DNA analysis.

Naylor believes both bites were accidental, from juvenile sharks following schools of fish.

"Perhaps incorrectly, I'm putting these in the bin of naive young sharks," Naylor said. "I'm sure the children who were bitten were petrified, but the sharks probably were, too."

He said sand tigers can grow up to 500 pounds but rarely bite humans. Naylor said about 70 percent of shark bites are from unidentified species, but great whites, tiger sharks and bull sharks are often assumed to be responsible because of their large size and the fact that they're involved in most of the identifiable bites. He said using DNA analysis could help identify other species responsible for anonymous bites.

Shark attacks in New York are rare, Naylor said, but when large schools of bait fish head for shore, predators follow and can accidentally bite people swimming in the water as they feed.

The last reported sand tiger bites near New York happened in 1988 and 1974, and the most recent attacks by unidentified species happened in 2015 and 2017, according to a shark attack file at the Florida Museum of Natural History