During the winter, manatees in Florida rely on warm-water refuges in the southern peninsula, and consistently return to one more specific areas. This new study assessed the proportion of manatees that use natural springs, power plant discharge areas, and passive 'thermal basins' that trap warm water for a week or more. They found that nearly half of all animals they counted sought out power plant outfalls for warmth, while approximately 17% chose warm springs. In the coldest periods the proportion at power plants can increase to two-thirds. Despite this relatively small proportion using warm-water springs, a comparison of manatees killed by cold weather revealed that hot springs offered them the best protection of the three refuges studied. The authors suggest that protecting and improving access to these warm springs may be critical for the long-term survival of Florida manatees.