Blue Spring is well known as a winter refuge for the Florida manatee. Manatees are gentle, slow-moving mammals related to the dugong, and more distantly, the elephant. They are herbivores and eat a wide variety of aquatic plants. Adults are
about 10 feet long and weigh between 1,500 and 2,200 pounds. During the warmer months, manatees travel widely through warm, shallow, coastal estuarine waters of central and south Florida. They cannot survive for extended periods
in water colder than about 68 degrees, so they migrate to warmer spring waters during the cold winter months.
The number of manatees using the Blue Spring run as a winter refuge is increasing. Since the mid-1980s, the winter population of manatees has increased almost fivefold, from less than 60 to more than 400 individuals. Manatees usually
arrive in small numbers as early as October and leave sometime in April, with the largest population using the spring run during December and January. Decreasing the volume of discharge from Blue Spring threatens wintering manatees by
reducing the size of the warm water refuge. Other threats to manatee survival in Florida are mostly due to human activities, such as operation of boats
and habitat degradation.