Dozens of false killer whales have died under mysterious circumstances after stranding themselves on a remote shoreline in Florida’s Everglades National Park.

The U.S. National Oceanic and Atmospheric Administration (NOAA) Fisheries Service reports that 95 false killer whales stranded themselves at Hog Key, on Florida’s southwestern coast. Since the U.S. Coast Guard spotted the animals on Saturday, 82 of the animals have died. The Miami Herald reports that the stranding was the largest for false killer whales ever recorded in the state.

False killer whales are the fourth-largest members of Delphinidae—the family of aquatic mammals comprising dolphins—and can grow between 16 to 20 feet long. They look similar to killer whales but lack orcas’ distinctive white spots. While false