Five pilot whales that beached on Edisto Island over the weekend were members of a larger pod that apparently stranded twice along the Georgia coast since July.
In Georgia, the whales swam free or were pushed back to sea by people trying to help.
Wildlife biologists cautioned the strandings might not be over. People are encouraged not to approach the animals, which might be diseased, but to instead alert the S.C. Department of Natural Resources.
"We're definitely on the alert. We are definitely concerned," said Lauren Rust, of the Lowcountry Marine Mammal Network. "The whole thing is definitely unusual."
Four whales were stranded on Edisto Beach when beachgoers found them early Saturday. A fifth stranded later in the day. They were alive but were euthanized by a veterinarian. Blood and other forensics testing samples were drawn. One had a complete necropsy performed, Rust said.
There were no obvious signs of injury or sickness, she said. The whales were weak, likely to strand again and vulnerable as prey.
"These animals had been on land for hours before anybody got to them," she said. "These are an offshore species. They should be 100 miles offshore."
The whales were buried by the Edisto Beach Public Works Department.
Georgia Department of Natural Resources wildlife biologist Clay George confirmed that fins from three of the Edisto whales match whales that stranded on St. Catherine's Island earlier in September. He's confident it's the same pod.
In that stranding, at least 28 pilot whales were found in shallow waters on St. Catherine's on the mid-Georgia coast. The incident followed a July stranding of at least 20 pilot whales out of a pod of at least 50 off St. Simons Island just to the south.
In those two strandings at least 20 whales died.
A marine mammal such as a whale or dolphin strands when it is stressed and from a variety of factors, including being sick, chased by a predator, entangled in lines, struck by a boat, poisoned or disturbed by another man-made threat.
Short-finned pilot whales are 12- to 24-foot-long mammals that can weigh a ton or more. They are social animals that live together in large groups and tend to strand in multiple numbers for reasons that still puzzle researchers.
"When one strands, they strand together," Rust said.
A series of strandings along the Southeast coast from a single pod isn't unprecedented. In 1977, as many as 100 pilot whales beached and were tagged in Nassau County, Florida, just south of the Georgia line. Two of those animals stranded later at Rockville just north of Edisto Island.
"These animals (pilot whales) move great distances normally. The only difference is they normally do it far offshore along the Continental Shelf," George said.
Pilot whales don't often strand on the shallow-water South Carolina beaches, where pygmy sperm whales are more likely to be found; the sperm whales are a smaller, more coastal species.
Because pilot whales are deep-sea creatures, the strandings aren't considered to be related to a cargo ship that wrecked and overturned near St. Simons Sound in the beginning of September. Forensics researchers will look for other answers.
In a notorious 2005 incident, three dozen pilot, sperm and minke whales beached and died on the Outer Banks after five long sonar blasts were transmitted from about 200 miles away. A federal necropsy report did not find a cause for the strandings and said Navy sonar operations that took place shortly beforehand could not be ruled out.
Conservationists worry that sonar and other man-made noises could be deafening and frightening whales into lethal beach stranding and rapid surfacing. Whales communicate and are thought to navigate using whistles and echoes similar to sonar.