At least 82 dolphins, including juveniles and calves, have died in a mysterious incident in a remote section of Florida's Everglades National Park. Officials say 95 dolphins—a particular species known as false killer whales, which typically swim at depths of 3,000 feet—were seen stranded in the area beginning Saturday, and at least 72 died on their own. Another 10 were euthanized, reports Reuters. Officials are still trying to determine what happened to another 13 dolphins, but "I wouldn't be overly optimistic that they're still alive at this point," Erin Fougeres, an NOAA marine biologist, tells Popular Science. "They were high and dry on very wide mudflats and trapped in mangroves," she adds, per NBC Miami.
A response team tried to herd the dolphins to deep water but were unsuccessful, an official says. It isn't clear what led to the stranding, but the animals are known to strand in large groups. Two such strandings were reported in Florida in the 1980s, but never involving more than 40 dolphins, per NBC Miami. This case is "the largest mass stranding we've had of this species in the US," Fougeres says, though 835 false killer whales were stranded in Argentina in 1946. Necropsies are being conducted in the hope that they'll provide clues, but a Coast Guard captain presents one theory: "I think they were just cruising along, the tide dropped out, and they found themselves on the beach," he tells WBBH. (Read more dolphins stories.)