Status and Biogeography of the West Indian Manatee

Abstract

We review historical and recent information on the distribution, status, and habitat associations of the West Indian manatee, Trichechus manatus, summarize threats to its continued survival, and discuss some biogeographical patterns of trichechids. Historical accounts indicate that manatees were once more common and that hunting has been responsible for declining numbers throughout much of their range. Small numbers occur throughout the Greater Antilles, where opportunistic taking by fishermen is a major source of mortality. Populations in Haiti, the Dominican Republic, and Jamaica are particularly vulnerable. Manatees have not been documented to occur in the Lesser Antilles since the 18th century, except for rare sightings in the Virgin Islands. Manatee sightings in the Bahamas are also rare; however, a recent dispersal from the northwest coast of Florida to the Bahamas has been documented. Manatees are relatively abundant in Belize compared with other countries of Central America. They persist in some of the large river systems of South America: the Río Magdalena in Colombia, Río Orinoco in Venezuela, and probably the Río Mearim in Brazil. They are absent or scarce along most of the South American coast, except in the extensive coastal wetlands of Guyana and Suriname. At present, there are only three regions in Mexico where manatees are still commonly found. Manatees are widely distributed on both coasts of Florida, and some venture westward along the Gulf coast and northward along the Atlantic coast of the southeastern United States, primarily during the warm season. Heated industrial effluents along both coasts have influenced manatee distribution and migratory patterns in the United States. Illegal killing continues to threaten the survival of manatees in many countries. Despite protective measures to regulate boating activity, collision with boats is still the major cause of human-related manatee mortality in Florida. Habitat alteration is a growing concern in all countries.Manatees in the Greater Antilles and Central and South America belong to the same subspecies, T. manatus manatus. However, results of recent genetic analysis indicate greater similarity between the Florida manatee, T. manatus latirostris, and manatees in the Dominican Republic and Puerto Rico, than between the latter and manatees in South America. The highest genetic diversity is found along the northern coast of South America, at the core of the species' range; marginal populations (in Florida, Mexico, and Brazil) were each found to be monomorphic (only one haplotype apiece) although distinct from one another. Salinity, temperature, water depth, currents, shelter from wave action, and availability of vegetation are important determining factors of manatee distribution. The association of T. manatus with freshwater sources is a highly consistent pattern. Throughout most of their range, manatees appear to prefer rivers and estuaries to marine habitats. The Amazonian species, T. inunguis, may be restricted to the Amazon River because of in...

How do en route events around the Gulf of Mexico influence migratory landbird populations?

“…Sea turtle distributions were acquired from IUCN (2014) or State of the World's Sea Turtles (SWOT 2006, 2012). The sperm whale distribution was gathered from IUCN (2014) and the manatee distribution was digitized from multiple sources (Lefebvre et al 2001, SEMARNAT 2010, IWLearn 2014, Save The Manatee 2014.…”

Feeding preferences of West Indian manatees in Florida, Belize, and Puerto Rico as indicated by stable isotope analysis

“…Both subspecies appear to require regular year-round access to a freshwater source (Lefebvre et al 1989, Olivera-Gomez & Mellink 2005, a requirement that is likely a result of osmoregulatory constraints (Ortiz et al 1998(Ortiz et al , 1999. Winter habitat use by Florida manatees is primarily influenced by water temperature, whereby physiological constraints require that they aggregate at natural (springs) and/or artificial (power plant outflows) warm water sources when water temperatures drop below 20°C (Irvine 1983, Worthy et al 2000, Bossart et al 2003.…”

A Framework for Monitoring and Assessing Socioeconomics and Governance of Large Marine Ecosystems1 1First published by Sutinen et al. in 2000: NOAA Technical Memorandum, NMFS-NE-158 (under contract # ENN F7 00378)

“…comm.). Manatees are virtually unknown from the U.S. Virgin Islands (Lefebvre et al, 1989). A rare sighting and stranding was reported here in 1988 (Caribbean Stranding Network, unpubl.…”

“…The Antillean manatee is found in eastern Mexico, Central America, northern and eastern South America, and in the Greater Antilles (Lefebvre et al, 1989). In Puerto Rico, the manatee is most abundant along the south and east coasts, particularly in the area of Fajardo and Ceiba (Roosevelt Roads Naval Station) and in the Jobos Bay area between Guayama and Salinas.…”

“…Quantitative information is limited regarding trends in the abundance of the Antillean manatee, although "[h]istorical accounts indicate that manatees were once more common and that hunting has been responsible for declining numbers throughout much of their range" (Lefebvre et al, 1989).…”