[You can track online great white sharks Katherine and Betsy in the Gulf of Mexico.]
Researchers say Katherine the shark, weighing 2,300 pounds, is only about 100 miles southwest from the Florida coast, and Betsy, at 1,400 pounds, was last tracked earlier this month 120 miles west of Sanibel Island, Fla., as first reported by The Houston Chronicle.
It's unclear where these sharks are headed because great whites are so infrequently spotted in the Gulf of Mexico, said Bob Hueter, director of the Center for Shark Research at the Mote Marine Laboratory, in an interview with USA TODAY Network.
The two sharks were tagged in August off the coast of Cape Cod by not-for-profit research organization Ocearch. That means Katherine and Betsy have traveled nearly 5,000 miles.
Although great whites have been studied and tracked in the Pacific Ocean, the research now on the great whites of the Atlantic is nascent.
"Every animal is causing us to reset what we thought was going on," he said.
It's not even known the number of great whites in the Atlantic, Hueter said.
A 2011 study found only 219 great whites at two sites in the Eastern North Pacific, but new research, released this week by the the Florida Program for Shark Research, puts the estimate at closer to 2,000 or more sharks in the Eastern North Pacific.
Great whites are the largest known predatory fish. They are targeted by hunters for their fins and teeth, as well as trophy fishing. Some are also caught as a "bycatch" in commercial fisheries, according to the World Wildlife Fund.
Although not listed as an endangered species, great white sharks are considered a protected species.
But in order to protect them, researchers need a better understanding of where they travel to, mate and give birth -- all things not yet known about the great whites in the Atlantic, Hueter said.
"if they're vulnerable enough they require protection, just throwing that protection over them in one restrictive part of their range isn't good enough," Hueter said. "We've got to understand what home means for them."