Felice Knowles, researcher with the Bahamas Marine Mammal Research Organization (BMMRO) spoke at the Abaco Science Alliance Conference on January 7 about the movement patterns of West Indian Manatees (Trichechus manatus) in The Bahamas.
The BMMRO and the U.S. Geological Survey/Sirenia Project (USGS) have been monitoring the occurrence and health of West Indian manatees in The Bahamas for over fifteen years.
Through the use of photo-identification and the location and timing of sightings, as many as fifteen individual manatees are currently known to inhabit The Bahamas, three of which had previous sighting histories in Florida.
Three (Rita, Georgie, and Gina) were periodically radio-tagged to document their movements and habitat use patterns.
Historic evidence of manatees in The Bahamas is limited to only two sightings from 1904 and 1975, suggesting The Bahamas has not had a persistent manatee population. However, manatee sightings increased significantly during the 1990’s commensurate with the increase in the Florida manatee population, greater public awareness, and reporting of sightings to local environmental organisations, such as BMMRO.
Tracking and photo-identification data show persistent local resource use and occasional long-distance, deep-ocean movements between islands.
Rita was documented in Florida in 1988 up until 2008 but then moved to Eleuthera in 2009. Shortly after she arrived she had a calf – Georgie – on June 25, 2010. After Hurricane Irene hit the pair were seen in Nassau harbour. Because of safety concerns the Department of Marine Resources had the manatees relocated to Dolphin Cay were they were held, then radio tagged and later released.
Rita and Georgie, tagged as a mother-calf pair, were observed negotiating local habitats, making repeated moves from the Berry Islands to Andros Island.
Post-weaning, Georgie left the Berry Islands and twice traveled across the deep waters (some areas deeper than 3000 meters) of the Great Bahama Canyon to Abaco Island (minimum distance of 50km). Georgie travelled around the western side of Abaco and eventually making her way to Cherokee Sound.
After an illness required her to be captured and treated she was released in the Berry Islands, but not long after Georgie found her way back to Abaco and has been seen in the Cherokee and Casuarina area.
Gina resided in the northern Berry Islands for fourteen years, and then arrived in Eleuthera in 2014 (100 kilometers away) where she was tracked among nearshore habitats and making two, possibly exploratory movements 30 kilometers offshore into waters with depths greater than 4,000 meters.
An adult male, Blackbeard – original seen in Tampa Bay, Florida – has been photo-documented at Long, Cat, Eleuthera, and New Providence islands, with some repeated trips among these islands.
Photo-identification and radio-tracking of individual manatees in The Bahamas have provided insights in the navigational capabilities of individuals to occupy large home ranges, negotiate repeated long distance moves and survive deep-water crossings.