In 1982, another outbreak of red tide occurred in southwest Florida and was believed to have caused the deaths of 37 manatee. In the winter of 1989-90, at least 45 manatee deaths occurred from cold stress because of a prolonged cold front in December. During that time, temperatures in Florida's coastal waters dipped into the 40 and 50 degree Fahrenheit range. One of the problems manatees face is that their reproductive rate is slow. Scientists believe female manatees don't become sexually mature until around five years of age.
Males are mature at approximately nine years.
Manatee females usually bear one calf every two to five years, and twins are rare. Because the reproductive rate is so low, the species as a whole adapts very slowly to changing situations or unnatural stress. Any species of animal living in the wild will suffer losses from natural causes and can usually overcome those losses, but the manatee population must also deal with additional mortalities caused by human-related factors. FMRI statistics also show that most human-related manatee mortalities occur from collisions with watercraft.