Driven by plunging temperatures, hundreds of manatees stampeded south on the Intracoastal Waterway over the past two days toward the warm water of power plant discharges in Riviera Beach and Fort Lauderdale.
Cold snaps have emerged as a leading killer of manatees over the past three years, exceeding deaths by boat collisions, according to figures kept by the Florida Fish and Wildlife Conservation Commission.
“Manatees are tropical animals so they start to suffer when the water temperature goes below 68 degrees,” said Kathryn Curtin, a contract biologist for the U.S. Geological Survey based at Port Everglades.
An aerial count Wednesday in Broward County found 63 manatees heading toward Port Everglades, where the Florida Power & Light plant sucks in water for cooling and emits it at a higher temperature. A total of 472 manatees were counted in Broward Wednesday, and that number could climb to 800 or so if the cold weather continues, said Pat Quinn, the county’s manatee coordinator.
In Riviera Beach, where the power plant is offline for modernization, FPL provides heated water anyway for manatees that have learned to expect it. The company turned on the heaters for the first time Tuesday night, said Paul Davis, Palm Beach County’s manatee coordinator. Although hard numbers were not available, he said there were probably hundreds in the county, particularly around the plant.
At Port Everglades, manatees could be seen swimming around a basin popular with mothers with calves. Curtin said calves are particularly vulnerable to cold, making new mothers among the first to show up at the power plant when temperatures drop.
The Fish and Wildlife commission said Wednesday that cold weather killed 112 manatees last year, 282 in 2010 and 56 in 2009, much higher numbers than in previous years. Over the same three-year period, boats killed 258 manatees.
We are concerned about the number of manatee deaths the past three years, including those resulting from exposure to cold weather,” said Gil McRae, director of the commission’s Research Institute. “Over the next few years, we will use data from monitoring programs to better understand any long-term implications for the population.
The cold also makes manatees more vulnerable to collisions with boats, because they travel between power plant refuges and sources of food that could be miles away. Although Palm Beach County has extensive stands of sea grass, Broward does not, forcing manatees to travel long distances for meals.
At Port Everglades, Curtin works in a program that tracks manatees by the unique pattern of prop scars on their backs. She said 80-90 percent of manatees have these scars, which allow researchers to track manatees’ movements, calving and other aspects of their life histories.
Power plants became more important to manatees as natural sources of warm water dried up, due to human consumption or development.