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Lack of genetic diversity threatens manatees, study says

Published Dec. 19, 2012

The population of Florida's manatees, which have been on the endangered species list since 1967, has grown to somewhere between 4,000 and 5,000. As a result, U.S. Fish and Wildlife Service officials, facing a petition from a libertarian legal group, may take them off the endangered list.

But a new study, done by a research team from the University of Florida and the U.S. Geological Survey and announced Tuesday, suggests manatees' future is anything but assured.

The study, which began in 2007, looked at genetic samples from 362 manatees. Some samples came from dead manatees being examined at the state's lab in St. Petersburg, and some were snipped from the tails of calves in the wild, said lead author Kimberly Pause Tucker of Stevenson University near Baltimore.

What the scientists found is that the manatee population has a very low genetic diversity, Tucker said. If a disease were to hit the manatees, it could easily wipe them out. "Where there's some natural variations in the population, then you have some that are better able to resist," she explained.

The low diversity could also signal potential for inbreeding problems, such as in the Florida panther population.

Panthers had dwindled to about 20 animals, many suffering from birth defects such as holes in their hearts. The only thing that saved them from extinction was a bold experiment in 1995 that brought in eight Texas cougars to breed with the panthers. Now there are more than 100 panthers roaming South Florida.

So far, the manatees' lack of diversity has not produced any such effects. The population growth is "kind of a success story," Tucker said. Nevertheless, she said, while 5,000 manatees sounds like a lot, "that's not huge."

Because of the lack of diversity among their genes, she said, the study showed that it's as if there are only 1,500 manatees actually breeding.

For now, she said, the key will be in protecting their remaining habitat.

Last week the libertarian Pacific Legal Foundation petitioned the federal government to drop manatees down a peg from "endangered" to "threatened."

Federal officials had already been thinking about doing just that. The process of changing manatees' classification will likely begin in 2013, said Chuck Underwood of the U.S. Fish and Wildlife Service. Underwood said Tuesday that the genetic diversity research "is being factored in" to the agency's data collection.

To Pat Rose of the Save the Manatee Club, the study's findings show that manatees probably should stay on the endangered list. "Not only does the manatee's low genetic diversity signal that manatees were nearly wiped out by man but it also reminds us that the manatee's future is fraught with threats and risks from many sectors," he wrote in an e-mail.

Manatees have been on the endangered list since the first list was approved in 1967. Documents from that era show they were not classified as endangered based on their numbers, which were unknown, but because of the threats they faced from boats and losing their habitat to waterfront development.

Craig Pittman can be reached at craig@tampabay.com.

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