CHARLESTON — It seems Mary Lee’s winter vacation in the sunny South is over.

The 3,500-pound great white shark headed north after spending weeks off the Southeast coast. Mary Lee, one of only two great whites ever tagged in the North Atlantic, got as far south as Jacksonville Beach, Fla., several weeks ago. She was spotted off the Isle of Palms and other Lowcountry waters, too.

But in recent days, she’s made a bee line north.

Thursday, she was off Long Island, N.Y. Researchers can’t really say they are surprised because the habits of the great white are such a mystery.

“Lo and behold, Mary Lee goes down there for a little while and then bugs out and now she’s off Long Island and we realize we don’t know anything,” said Chris Fischer, the founder of OCEARCH, a nonprofit dedicated to studying great whites and other large marine species.

Fischer’s group has tagged dozens of great whites off South Africa and in the Pacific. He led the September expedition to tag Mary Lee off Cape Cod, and named the shark after his mother. The group also tagged a second great white, Genie, who also was spotted off the Lowcountry coast.

Capturing a great white weighing upward of 2 tons is no easy feat. The expedition used its 126-foot research vessel, designed with a special lift that can bring up 55,000 pounds.

“We bait the shark and once we are pulling on the shark we walk it back to the ship and over the lift. The lift then pulls it out of the water,” Fischer said. While on the boat, a device that relays the shark’s position to a satellite is attached to its dorsal fin.

As many as 100,000 people a day are monitoring the position on OCEARCH’s website. Traffic got so heavy this winter the organization had to upgrade its servers, Fischer said.

“This is modern day exploration. I wanted the public to be able to see a part of that,” he said.

The other great white, Genie, also headed south for the winter. But because she doesn’t surface as much, her travels have been harder to track. Genie’s last position was recorded Jan. 19 off the South Carolina-Georgia border.