(ENN) -- Out in the open ocean, a manatee -- the giant gentle vegetarian sea cow -- looks like an easy meal to predators -- big, slow and tasty. So Florida's manatees have made it a point to stick close to home, in coastal waters and rivers. But their isolation, while protecting them from becoming a tasty meal for a shark has also lead to dangerously low genetic diversity.

University of Florida researchers collected blood, skin and tissue samples from manatees in Florida, South and Central America, Mexico and the Caribbean. By looking at the genetic traits of the different manatees, biologists now believe a small number of Caribbean sea cows colonized Florida waters in the last 10,000 years. With only a few ancestors to start with, today's manatees could face inbreeding problems, making it harder for the species to cope.

"What we've learned is the Florida manatee is genetically unique, and that it's isolated from manatees elsewhere in the Caribbean and the Yucatan," said Brian Bowen, a conservation geneticist with the University of Florida Institute of Food and Agricultural Sciences. "Because of their low genetic diversity, it causes concern but not alarm."

"If the population crashes, they are gone," said Angelica Garcia, a UF graduate researcher working with the Sirenia Project, a federal agency that studies manatees. "It is unlikely that it will recover from a natural source of animals coming into Florida to repopulate."

Despite the manatee's ability to swim large stretches of water, the population tends to stay put because of its dependence on specific habitat features. The vegetarian animals prefer protected coastal waters and rivers, where sea grasses or fresh water vegetation are abundant, said Bowen, who is supervising Garcia's research.

"What we've learned is the Florida manatee is genetically unique, and that it's isolated from manatees elsewhere in the Caribbean and the Yucatan."
-- Brian Bowen, University of Florida conservation geneticist

"It's very much against their well-being to travel across open water," Bowen said. "Out there, they are big, slow and tasty. We think they are just a big shark egg roll, and that's one of the reasons they don't move much between their different habitats in the West Atlantic."

With probably 2,000 to 3,000 manatees left in Florida, Bowen said the population still is healthy, but their population trend must be watched closely. Low genetic diversity could make them more susceptible to diseases and more sensitive to climate changes.

"The keys to manatee conservation are in the collection of accurate information on population and environment trends and effective law enforcement," said Robert Bonde, a biologist with the Sirenia Project.

The leading causes of death among Florida manatees are human-related, Bonde said. These include collisions with boat propellers, entanglement in float and fishing lines and ingestion of foreign objects, such as garbage thrown from boats.

"It's critical that boaters slow down when they travel in manatee zones," he said. "It's also critical that we protect the manatees' habitat. For example, the sea grasses that they feed on are very susceptible to reduced light levels, which can be caused by pollution and fertilizer run-off."

"The bad news for the Florida manatee is that they're on their own," Bowen said. "They're not going to get help from neighboring manatees in their plight to survive and persist in Florida.

"The good news is that we know about it before it's too late."

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