From: David A Gabel, ENN
Published October 24, 2012 08:53 AM

Puerto Rican Manatees Suffering from Lack of Genetic Diversity

There are multiple manatee populations in the Caribbean, but new evidence shows that they are isolated with no cross-breeding going on. The endangered marine mammal, known as the sea cow, is a species protected by law and is listed by the World Conservation Union as vulnerable to extinction. A new study conducted by the US Geological Survey (USGS) and the Puerto Rico Manatee Conservation Center (PRMCC) focusing on the West Indian manatees came to the conclusion that manatee preservation is being hampered by their lack of genetic diversity.  Their findings will hopefully aid resource managers to make more informed decisions on how to protect the manatees.

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Manatees are very large creatures, weighing up to 1,300 pounds (590 kg). They behave much like cows, munching on sea grasses and other plant material all day, grazing at a depth of 1-2 meters and surfacing for air several times per hour. They inhabit shallow, marshy coastal areas and rivers in the tropics. Their three main areas of distribution are the West Indies, Amazon, and West Africa.

The USGS/PRMCC focused solely on the manatees of the West Indies. They found that there was no cross-breeding between manatees of Puerto Rico and those in Florida. This is resulting in a lower genetic diversity in Puerto Rico's fragile manatee population, decreasing its odds for survival.

"Wildlife management has been one of the fields to benefit greatly from the ability to determine relatedness of individuals from DNA analysis, allowing management decisions to be based on concrete scientific evidence for genetic diversity and prospects for it to increase," said USGS Director Marcia McNutt. "These results for Puerto Rico's manatees are a wake-up call."

Wildlife authorities estimate about 250 individual manatees living in the waters of Puerto Rico. Coupled with a severe lack of diversity, the population has become extremely vulnerable to natural and man-made disasters. For example, after a major incident like a hurricane, disease, or boat strikes, which can kill a large number of manatees, there may not be enough left to rebound. Losses are not being offset by migration of the Florida manatees.

There is also little hope of migrants to Puerto Rico from other Caribbean islands such as Jamaica, the Dominican Republic, and elsewhere. Smaller islands of the lesser Antilles such as Guadeloupe and the Virgin Islands have already lost all their manatees.

Furthermore, the genetic study has found that there are actually two distinct manatee populations within Puerto Rico itself, but that the two very seldom interbreed, further decreasing the genetic diversity.

Inbreeding is never healthy for any species. To maintain a healthy population, manatees need to mate with other manatees not within their own circle. Otherwise, the species is likely to stagnate and die. Studies like this are important for conservationists to understand the problem and work towards the solution. Hopefully the manatees of the West Indians will bounce back to a sustainable population size and a healthier dynamic.

This study has been published in the journal Conservation Genetics

Manatee image via Shutterstock

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