A new study suggests that Puerto Rico's small manatee population has a low genetic diversity, which poses a threat to their long-term survival.

Latest estimates show there may be around 250 individual manatees living in Puerto Rico. Experts from the U.S. Geological Survey and Puerto Rico Manatee Conservation Center studied the current breeding rates by comparing the Florida and Puerto Rico manatee populations using nuclear DNA.

New evidence shows that the Puerto Rican manatees are not cross-breeding with the manatees living in Florida, resulting in low genetic diversity.

Earlier conservationists hoped that the endangered species will be able to rebound through migration and mating. But the new evidence shows that the animals lack gene diversity, making them vulnerable to future environmental changes and natural disasters like hurricanes or boat strikes.

"Puerto Rico's Antillean manatees have low overall numbers and low genetic diversity, both of which present risks for the population's long-term survival," Margaret Hunter, a USGS geneticist and lead author of the study, said in a statement.

"The lack of gene flow is another risk factor. We detected no signs that the Puerto Rico population is being supplemented by Florida manatees, through migration or breeding. This means that Puerto Rico's population must absorb shocks - such as environmental change or disease - on their own. It's a trifecta of genetic vulnerability," she said.

Apart from these findings, experts also revealed that there are two different manatee populations in Puerto Rico itself that do not inter-breed with each other. The two types of animals are genetically diverse which could help improve the long-term prospects for manatees in Puerto Rico.

Puerto Rican manatees are not only detached from the Florida manatees, but they don't receive migrants from nearby islands.

Experts hope the study will help managers to make better decisions to conserve the endangered species. "The more that we continue to learn about this unique mammal, the better we can enable managers to make decisions that ensure adequate protection," said Bob Bonde, a USGS research biologist and co-author of the research.

The findings of the study are published in the journal Conservation Genetics.