The seasonal distribution of the West Indian manatee varies with water temperatures. Temperatures below approximately 20 °C (68 °F) increase the risk of cold-induced stress or mortality for manatees. Consequently, Florida manatees seek out warm-water refuges during the winter, concentrated primarily along the Florida peninsula. Many of these refuges are artificial, created by the runoff from nearby power plants. In contrast, the Antillean manatee is less susceptible to cold-induced stress due to the warmer waters across its range. Florida manatees inhabit the most northern limit of sirenian habitats. There are four recognized subpopulations of the Florida manatee, termed the Northwest, Southwest, Atlantic Coast and St. John's River populations. Large concentrations of Florida manatees are located in the Crystal River and Blue Springs regions in central and north Florida. The Antillean manatee is sparsely distributed throughout the Caribbean and the northwestern Atlantic Ocean, from Mexico, east to the Greater Antilles, and south to Brazil. Populations can also be found in The Bahamas, French Guiana, Suriname, Guyana, Trinidad, Venezuela, Colombia, Panama, Costa Rica, Curaçao, Nicaragua, Honduras, Guatemala, Belize, Cuba, the Dominican Republic, Jamaica and Puerto Rico. It is possibly extirpated from the Turks and Caicos Islands, and definitively so from all the Lesser Antilles except Trinidad and Curaçao. Its presence in Haiti is uncertain. Behavior and diet Behavior Because manatees evolved in habitats without natural predators, they lack predator avoidance behavior. The large size and low metabolic rates of manatees lends to their capacity for long and deep dives, as well as their relative lack of speed. Manatees are frequently solitary creatures, but they do aggregate at warm-water habitats during the winter and during the formation of breeding herds. In spite of their docile demeanor, due to their large size the West Indian manatee has nearly no natural predators in its native environment. American alligators and American crocodiles have been suspected to on occasion take a manatee. A dying manatee was discovered in Puerto Rico, wounded by a large shark bite thought to be inflicted by either a tiger shark or bull shark. It is projected that large sharks may threaten manatees occasionally but rarely enter the manatee's brackish habitats, whereas marine mammals in more direct coastal oceanic waters are well known to be highly vulnerable to sharks and orcas. Communication Manatees have been shown to form large mating herds when males come across estrous females, indicating that males may be able