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.
Manatees are slow moving animals.
Because they have no natural enemies, they never developed speed as a defense mechanism. Manatees can swim up to 20 miles per hour in short bursts, but usually only swim about three to five miles per hour. Because manatees are mammals, they need to surface to breathe air. They also prefer shallow waters where they feed on submerged seagrasses. All of these factors combine to make them vulnerable to boat hits.