Early this past winter, Martine de Wit noticed a spike in the number of manatees that were dying. At first, the veterinarian with the Florida Fish and Wildlife Conservation Commission attributed the surge to cold stress. De Wit was used to seeing some manatees sickened by the strain put on their sensitive bodies when water temperatures dip below 68 degrees Fahrenheit, as they did several times in December and January.

“But as winter progressed, something seemed off,” says de Wit, whose lab is located in St. Petersburg. So far in 2021, more than 430 manatees have perished in Florida’s waters, almost triple the count for the same period the year before.

Recent cold snaps forced these temperature-sensitive mammals to seek