The large group of whales was first spotted Tuesday in very shallow water in Everglades National Park. Those that died are being studied for the reasons they beached themselves.
The short-finned pilot whale is a deep-water species that cannot survive long in the shallows.
Six whales were found dead in the remote area on the park's western edge, and four had to be euthanized. The whales were first spotted Tuesday about 20 miles (32 kilometers) east of where they normally live. It takes more than an hour to reach the spot from the nearest boat ramp and there is no cellphone service, complicating rescue efforts.
Teams from NOAA, the National Park Service, the Coast Guard and state wildlife agencies were working to prevent any more whales from stranding. The animals had not been cooperating Wednesday, when most were in about 3 feet of water.
The short-finned pilot whales typically live in very deep water. Even if rescuers were able to begin nudging the 41 remaining whales out to sea, they would encounter a series of sandbars and patches of shallow water along the way.
The species also is known for its close-knit social groups: If one whale gets stuck or stays behind, the others are likely to stay or even beach themselves as well.
"It would be very difficult for the whales to navigate out on their own," Mase said.
Federal officials were notified about the whales Tuesday around 4 p.m. Because of the remote location, workers were unable to access the site before dark. They arrived Wednesday morning and discovered 45 whales still alive.
"There were some that were very compromised and in very poor condition," Mase said.
Four were euthanized with sedatives, and more could be put down Thursday if their condition deteriorates, Mase said. She described the remaining whales as swimming and mobile but said scientists don't know how long they've been out of the deep, colder water. She said they could be affected by secondary consequences, such as dehydration.
"I don't think we have a lot of time," Mase said.
Mase confirmed Thursday that sharks had begun to feed on the dead whales. Necropsies were being done Wednesday, and scientists will look for disease or other signs to indicate how whales got stuck in the shallow Everglades waters.