One of two manatees released into the Caribbean in August under a pioneering repopulation scheme has died of a suspected kidney infection, the Guadeloupe National Park announced Monday.

Junior was one of two Singapore-born male manatees or sea cows flown half-way around the world in the effort to restore West Indian populations of the slow-moving herbivores.

Confirming the animal's death, Guadeloupe National Park director Maurice Anselme said tissue samples would be analyzed to determine the cause of death.

During a check-up Friday, veterinarians noticed that Junior had "lost a lot of weight," with blood tests showing he had suffered kidney failure, the park said in a statement.

Urgent treatment failed to save the mammal, which was pronounced dead on Sunday afternoon, the park added.

"We did everything we could," Anselme said, assuring that Junior's fellow traveler Kai was "doing well" and that his blood tests were "normal".

The manatees, which weighed between 500 and 700 kilogrammes (1,100 and 1,540 pounds), were born and bred at Singapore Zoo.

Their arrival in Guadeloupe, where they were released into a protected bay, marked the culmination of a decade-long effort to reintroduce the gentle giants in the area.

Known locally as "maman d'lo" or mother of the sea, the West Indian manatee was an important part of the French Caribbean island's ecology before being hunted to extinction in the early 1900s.

Anselme said he was confident the EU-funded programme to bring 13 other manatees to Guadeloupe from zoos around the world over the next five years, 10 of them female, would continue.

Any offspring from the group will be released into the wild.

The manatee is listed as "vulnerable" on the International Union for Conservation of Nature's Red List of Threatened Species.