Manatees congregate in a canal where discharge from a nearby Florida Power & Light plant warms the water in Fort Lauderdale, Fla. Tuesday, Dec. 28, 2010. Overnight temperatures in South Florida were in the 30s. (AP Photo/Lynne Sladky)

(AP) -- People aren't the only ones in Florida who don't like cold weather. Manatees - those giant aquatic mammals with the flat, paddle-shaped tails - are swimming out of the chilly Gulf of Mexico waters and into warmer springs and power plant discharge canals. On Tuesday, more than 300 manatees floated in the outflow of Tampa Electric's Big Bend Power Station.

"It's like a warm bathtub for them," said Wendy Anastasiou, an environmental specialist at the power station's manatee viewing center. "They come in here and hang out and loll around."

Cold weather can weaken manatees' immune systems and eventually kill them. State officials said 2010 has been a deadly year for the beloved animals: between Jan. 1 and Dec. 17, 246 manatees died from so-called "cold stress." During the same time period in 2009, only 55 manatees died from the cold. In 2008, only 22 manatees succumbed to chilly temperatures.

Manatee deaths documented from Jan. 1 through Dec. 5 are nearly double the five-year average for that time period, according to Florida Fish and Wildlife Conservation Commission statistics.

"Obviously we're very concerned as an agency about the unusually high number of manatee deaths this year," said Wendy Quigley, a spokeswoman with the state-run Fish and Wildlife Research Institute in St. Petersburg.

A total of 699 manatees were found dead between Jan. 1 and Dec. 5; state officials say it's likely the cold temperatures also contributed to many of the 203 deaths in the "undetermined" category and the 68 deaths of manatees whose bodies could not be recovered.

Quigley noted that the statistics don't even include this week's cold snap, which sent temperatures plummeting into the 30s in parts of South Florida overnight and into the teens in the central part of the state.

Tampa Bay and Gulf water temperatures are hovering around 50 degrees, said Anastasiou. When the water dips below 68, manatees seek warmer waters - usually springs or the power plant discharge canals. The water temperature in the power plant's Big Bend canal ranges from about 65-75 degrees, Anastasiou said. Even though they're huge animals, manatees are very cold sensitive.

"They're not blubbery mammals. They're very lean mammals," Anastasiou said. "They need the warmth. They need a warm place to go."

The herbivores will brave the cold temperatures to forage for sea grass but will sometimes stay in the warm canal without eating for days.

Adult manatees can weigh up to 1,200 pounds and grow to be 10 feet long. During the warmer months, manatees leave Florida and can be found as far west as Texas and as far north as Massachusetts - although sightings along the Gulf Coast and near the Carolinas are also common.

During last year's cold snap, some 329 manatees congregated at the Tampa Electric power station. In Broward County on Tuesday, some 50 manatees gathered in the outfall of a Florida Power and Light plant.

State officials are also warning boaters to slow down and be on the lookout for manatees in the warmer, shallow water, where the mammals can fall victim to boat propellers. Hundreds have been spotted in local waters, state wildlife officials said.

Officials say most of the manatees were in the warmer waters near Florida Power and Light's power plants. However, some small groups were spotted in the Intracoastal Waterway.

Meanwhile Tuesday in coastal Mobile, Ala., a 700-pound manatee died during a rescue attempt.

Ruth Carmichael, head of the manatee program at the Dauphin Island Sea Lab, said she and a team from the Mobile Manatees Sighting Network wrapped the animal in warm towels when they were called Saturday to a Mobile Bay beach.

Carmichael said rescuers used a stretcher made of car towing straps to move the manatee onto a trailer, and had hoped to haul the animal to the Institute of Marine Mammal Studies in Gulfport, Miss.

The young male was supposed to have migrated to Florida waters about two months ago, though it was unclear if the animal died because of chilly conditions, Carmichael said.

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