Manatees in the Gulf of Mexico

The endangered Florida manatee (Trichechus manatus latirostris) inhabits rivers and estuaries along both coasts of Florida and, to a lesser extent, adjacent states (Figure 1). Since 1990, documented sightings of manatees outside of Florida have been increasing. This increase in sightings probably represents northward shifts in manatee distribution made possible by man-made sources of warm water (i.e., industrial effluents), as well as a decade of relatively warm winters. The most likely source of emigrants on the Gulf coast is the population of manatees that overwinter in the headwaters of the Crystal and Homosassa Rivers, Citrus County, FL. This group of manatees has undergone a steady increase in numbers, (approximately 7% per year from 1977-1991; Eberhardt and O’Shea 1995). Some emigrants may also come from the Tampa-Ft. Myers region, where human impacts on habitat are greater. Manatees are intelligent, long-lived mammals that appear to adapt readily to new environments and situations. However, manatees have relatively low metabolic rates, and cold winter temperatures restrict their northern distribution.