(Adds suspension of rescue effort at nightfall, paragraphs 9-10)
By Jane Sutton
MIAMI, Dec 4 (Reuters) - Ten beached whales have died and rescuers were trying to save dozens more that were swimming in dangerously shallow waters near shore in Everglades National Park in southwest Florida, park and wildlife officials said on Wednesday.
The National Oceanic and Atmospheric Administration, or NOAA, said wildlife officers euthanized four whales because they could not be saved, and rescuers tried with little success to coax another 41 whales out into deeper water.
NOAA said via Twitter that survival rates were typically low in such instances.
The whales were first sighted on Tuesday afternoon in a remote part of the park near the Gulf of Mexico, park spokeswoman Linda Friar said.
They were believed to be short-finned pilot whales, typically found in deep water in tropical and temperate areas. Biologists will perform necropsies on the dead whales to try to determine why they were stranded, NOAA said.
"Pilot whales are common stranders. They tend to do this," Friar said. When rescued, she said, "they tend to rebeach themselves."
"This area of the park is probably the most challenging for something like this. When the tide goes out, there's hundreds of yards of very shallow shoals," Friar said.
Short-finned pilot whales typically travel in pods of 25 to 30 animals. Adults weigh 2,200 to 6,600 pounds (1,000 to 3,000 kg), with females averaging 12 feet long (3.7 meters) and males averaging 18 feet long (5.5 meters), according to NOAA.
Efforts to save the whales by pushing them past an obstacle course of sandbars and back out to sea were suspended at nightfall on Wednesday, wildlife officers told reporters.
They said the rescue efforts were set to resume as needed early on Thursday morning. (Editing by Bernadette Baum. Cynthia Johnston, Grant McCool and David Gregorio)