Rare giants -- 40-ton right whales -- have returned to Lowcountry waters.
The endangered species will be out there all winter, and boaters are urged to be cautious. As recently as two years ago, an aerial survey team spotted one of the whales off Hilton Head Island with a gaping wound across its back, probably from the propeller of a recreational boat.
Such strikes are considered a leading threat to the 50-foot-long animals, said to be on the brink of extinction.
People tend to think something so large would be easy to see, but right whales aren't.
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"Right whales are dark with no dorsal fin, and they often swim slowly at or just below the water's surface," said Barb Zoodsma, right whale recovery program coordinator in the Southeast for the U.S. National Oceanic and Atmospheric Administration.
"Just a slight difference in the texture on the water's surface is often the only clue that a whale is present," Zoodsma said.
Each fall, females and a few males head south from their Great Banks feeding grounds to give birth and to winter in the warmer waters of the Southeast. Year to year, dozens are spotted in waters off South Carolina, some with newborn calves.
Wayne McFee, a National Ocean Service marine biologist in Charleston, said the whales typically pass through the Lowcountry and continue south, but "some animals tend to hang out" off local shores until about March, when they return north. In other southern waters, the whales get close to shore, but in South Carolina's waters they tend to stay several miles off the coast.
"Because they're endangered, we'd like for them not to be seen," McFee said.
He said boaters should keep 500 yards away from any right whales they see. One distinguishing mark is the V-shaped mist they exhale, McFee said.
The whales' route is heavily trafficked with boats and ships. An NOAA rule requires large ships to slow to half-speed within 23 miles of the coast in months when the whales are present.
Shipping companies have been cited for violations, including at least two operating off Charleston.
Right whale sightings already have been reported this year off South Carolina and Georgia, said Allison Garrett of NOAA.
A Sea to Shore Alliance team flying out of Charleston is part of a network trying to keep track of the whales, in part so ships know when they are around.
Right whales were nearly wiped out by whalers in the 19th century. Only about 400 are known to exist today, so few that researchers consider every whale vital to the survival of the species.
Packet and Gazette staff writer Erin Moody contributed to this report.