Frigid waters off the coast of Florida have killed a record number of endangered manatees this year, according to state wildlife officials. The manatee—full name, the West Indian manatee (Trichechus manatus)—has been protected by the Endangered Species Act since 1974.

As of December 10, 699 manatee deaths had been documented this year in Florida waters, 244 of which were attributed to "cold stress." Most of the year's deaths occurred in January during what the National Weather Service called Florida's coldest 12-day period since 1940.

This year's death toll tops last year's record of 429 deaths, 56 of which were caused by unusually cold weather. That was more than twice the number of cold-related deaths in 2008.

These numbers don't count manatee deaths outside of Florida. The "sea cows," as they are often called, do roam as far as Texas, and two were found dead in cold Mississippi waters this past week.

Part of the problem for manatees is that they have had to change their regular habitats and migration patterns to coexist with humans. According to the Save the Manatee Club, "coastal development pressures in southeast and southwest Florida have pushed manatees further north." Meanwhile, the vast number of power plants heating the water in areas along the Florida coast has allowed the manatees to stay further north instead of migrating south for the winter, which puts them at risk of hypothermia when temperatures drop.

One area where manatees migrate for warmth is the Big Bend Power Station operated by Tampa Electric. Earlier this week, more than 300 live manatees were counted near the power station's discharge canals, where water temperatures stay as high as 75 degrees Fahrenheit, according to the Associated Press. Another 100 were seen this week in a canal near Satellite Beach, where the waters were 25 degrees warmer than the nearby Banana River, which was just 50 degrees F. Water temperatures below 68 degrees F can be deadly to manatees.

Keeping manatees warm in the winter comes with a price. The animals continue to congregate in the Indian River Lagoon (along the state's Atlantic coast) where a power plant stood until earlier this year, when it was demolished. In the absence of a power plant, Florida Power and Light is now spending up to $550 an hour to artificially heat the lagoon, according to a report from local news station WESH. Manatees have been migrating to the lagoon's warm waters for more than 40 years.

The biggest gathering of manatees was further south in Palm Beach County, where an aerial survey last week counted more than 800 manatees, the highest number ever counted in the region in a single fly-over, according to the Florida Fish and Wildlife Conservation Commission (FWC). This caused the FWC to increase patrols to enforce boating speed limits and to warn boaters to be cautious and look for manatees while on the water. "It's a good thing the manatees are moving further south so they might be able to better protect themselves from the cold, but there's concern because this is expected to be a big boating weekend," FWC spokeswoman Gabriella Ferraro told the Palm Beach Post News.

The majority of manatee deaths are caused by watercraft. FWC officials say this year's death-by-boat count, while not yet final, is expected to be on par with last year, when 97 manatees were killed by boaters.

Photo by Thomas Bucher via fotopedia