By T. Rees Shapiro

Their names are Mary Lee, Katharine and Hilton. During the summer months, they like to hang out relatively close to beaches along the Mid-Atlantic. They are great swimmers. And they feast on the flesh of grey seals.

Also, they are great white sharks.

Just in time for the Discovery Channel's "Shark Week," as many people are seeking relief from the heat at beaches in Delaware, Maryland and New Jersey, OCEARCH, a nonprofit that tracks the movements of sharks, has logged a number of "pings" from great whites tagged with receivers in their dorsal fins.


Les Kaufman, a Boston University biology professor and shark expert, said that while the number of sharks in the water is believed to be dropping, the kind of technology used by OCEARCH makes it easier for nonscientists to track them, including via an iPhone app.

"Scientists know that the sharks are out there," Kaufman said. "It becomes news when nonscientists are encountering them . . . with advances in the technology there's a greater awareness."

In recent years, OCEARCH has tracked about 300 sharks, including mako and tiger sharks. They tend to swim north in the summer, as the hot weather warms the waters off the East Coast. But while they may sometimes venture near shore, sharks more typically swim kilometres away from the coastline.

Kaufman said a 4m-long shark generally would not swim in water less than 1m deep. In the entire world last year, he noted, only four people died from shark attacks. Many, many more people are killed from complications of insect bites.

"Mosquitoes, I mean my god!" Kaufman said. "Malaria takes a huge chunk of humanity every year, and sharks don't."

OCEARCH followed a 590kg male named Hilton who measures about 3.6m from teeth to tail from the coast of Ocean City to the Jersey Shore.

Other great whites spotted along the East Coast in the last 30 days include Miss Costa, a 725kg, 3.6m female recorded near Nantucket, Massachusetts; Katharine, a 1043kg, 4.2m whose location was noted close to Virginia Beach; and Cisco, a young, 2.4m male who spent Memorial Day weekend in the waters between Lewes, Delaware, and Cape May, New Jersey, and just appeared in Nantucket.

Mary Lee, a 4.8m great white, who at 1564kg is about the size of a Toyota Camry, has 125,000 followers on Twitter and was last "pinged" in mid-June near the Jersey Shore. She spent this past winter near Savannah, Georgia, and has traveled as far as Bermuda since she was tagged in September 2012 off Cape Cod.


While great whites in particular are known as fearsome predators, thanks to movies such as Jaws, Kaufman said people should remember that humans have caused much more damage to sharks by overfishing.

"We have absolutely raped and devastated the global ocean," Kaufman said.

Still, if you happen to be swimming in the middle of a grey seal colony, like those near Cape Cod, the balance of power could shift, Kaufman said.

"That's a shark cafe," Kaufman said. "A high-end shark restaurant."