Wildlife officials were trying to determine why more whales stranded themselves in Florida over the weekend and died, but some sad details were emerging Monday. 

The 11 pilot whales found dead Sunday in the Florida Keys were all female or young calves, and they all came ashore within feet of one another on a small beach, the National Oceanic and Atmospheric Administration's Fisheries Service said Monday. Two of the females were pregnant.

The pilot whales discovered in the Keys appeared to be part of the same group of 51 whales that had been stranded last week in the Florida Everglades, about 70 miles away, where another 11 whales -- eight females and three males -- died after beaching themselves.

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Twenty-nine pilot whales from the pod were unaccounted for. Researchers were trying to solve the mystery of whether disease or something else drove the whales into shallow waters.

One of the peculiarities of the pilot whale as a species is that pods tend to be highly social and close-knit, sometimes refusing to leave sick members and sometimes beaching en masse.

Another group of pilot whales stranded themselves near Fort Pierce, Fla., last year, officials said, as did a group at Florida's Cudjoe Key in 2011. Similar beachings have been documented for decades. In last year's incident, at least 17 of the 22 whales in the pod died.

The pilot whales discovered dead Sunday had markings similar to those of whales that became stranded in the Everglades, indicating they were part of the same pod, officials said.

They were malnourished and emaciated -- but officials couldn't say whether that was because of disease or spending too much time outside their natural habitat in deep waters. Pilot whales often feed on squid at a depth of 1,000 feet or deeper, according to the fisheries service.

But the discovery that other members of the pod had wandered down along the curvature of the Florida coast and beached themselves on the Keys was not surprising, one official said.

"It’s basically history repeating itself," Blair Mase, NOAA's southeast region marine mammal stranding coordinator, told reporters Monday. "When they do strand in that southwest Florida coast, we have seen them also come down to the Keys as well.... If they all don’t strand at the same time, they would end up in this general location."

Scientists were performing necropsies on the dead whales Monday to look for clues.

Mase said the U.S. Navy had not been sending out sonar "pings" in the area, which can affect marine wildlife. Some studies have loosely, but not definitively, connected sonic disturbances to pilot whale strandings, according to the IUCN Red List of Threatened Species. The pilot whale is not considered endangered.

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