An adventurous gray seal that swam up the Hudson River past Albany last summer has left the Empire State for New England, according to satellite tracking data.

The male seal headed northeast after being released into the Atlantic Ocean at Ponquogue Beach in Hampton Bays on Dec. 10, according to the Riverhead Foundation for Marine Research and Preservation, which set him free. Eighteen days later he had arrived in Cape Cod Bay.

“It definitely looks like it knows where it’s going,” said Robert DiGiovanni, Jr., executive director and senior biologist of the foundation. “How it does that is something that’s not very well understood.”

Satellite tracking data shows the seal swam 218 miles since its release. The seafaring mammal swam along the Long Island coast, then past Block Island to Rhode Island before moving on through the Cape Cod Canal.

Nearby Muskeget Island, off Nantucket, is home to one of five gray seal colonies on the U.S. Atlantic coast where the mammals are known to breed, according to National Oceanic and Atmospheric Administration.

Dec. 28, 2015 tracking map of the seal. Photo Credit: Riverehead Foundation for Marine

“It knows where all the good places to hang out are,” DiGiovanni said.

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The seal was first reported to the foundation in April, when it was injured and trapped in a jetty at Robert Moses State Park. The foundation rehabilitated the animal and named it “Professor X” after the X-Men comic book character Professor Charles Xavier.

After tagging the seal, the foundation released it into the Atlantic Ocean in July. Less than two weeks later, a seal was reported in a canal lock in upstate Waterford, a town about 12 miles north of Albany. Locals dubbed him “Charlie.” The canal was due to be pumped out for maintenance and on December 4 the foundation recovered the seal, which the tag showed was the same “Professor X” they had released months earlier.

DiGiovanni said they’ve seen seals go up the Hudson, but “I don’t recall ever having anything that far up before.”

The seal was healthy when they brought it back to the foundation, which operates at the Long Island Aquarium & Exhibition Center in Riverhead, and he was released quickly, DiGiovanni said.

More than a century of hunting and bounties drastically reduced the gray seal population off the Atlantic coast in the United States and Canada. Since the 1970s, when they became protected under federal law, they have been making a come back, migrating from a colony off Sable Island near Nova Scotia. A 2015 NOAA report said that five pups were born on Muskeget Island in 1988. An aerial survey in 2008 recorded 2,095 pups on the island.

The foundation uses satellite tracking on six or seven seals a year, he said. The number they can track is limited by cost: the price of attaching a tracker and collecting satellite data on a seal for up to a year is about $5,000. The tracker is attached to the seal’s fur and only transmits when the seal is on the surface.

Andrea Bogomolni, a researcher at the Woods Hole Oceanographic Institution in Massachusetts, said satellite tracking is changing the understanding of seals’ resilience and their role in the ecosystem.

“These large animals that are able to come back again, that in itself is telling us the ecology role,” Bogomolni said. “That this system can sustain this growth of large, top predators.”