Unusually cold weather last winter killed Florida’s endangered manatees at a record rate, a report said on Friday.

During 2010, a record 699 manatees have died in Florida, according to the Florida Fish and Wildlife Conservation Commission’s Research Institute.

Of those, 244 were attributed to cold weather and many of the 271 undetermined deaths were also likely caused by weather. In most years, the leading cause of manatee deaths is from collisions with power boats.

The latest surveys estimate there are only about 5,000 of the chubby marine mammals left in Florida waters.