The manatee’s closest living relative is the elephant, and the two share several features, including a flexible prehensile structure used to grasp vegetation and place it in the mouth, herbivorous diets, nursing of calves from behind the forelimbs, prolonged maternal care, thick hide with hair covering the body, and toenails. Female manatees reach sexual maturity at age 3 but do not breed successfully until 6 to 10 years of age, while males are sexually mature at age 2. Manatee mating herds include sexually mature males and females, with more males than females, and many males may court one female for from a week to one month, with only persistent males succeeding. Manatees reproduce very slowly: females carry young for up to 13 months, usually give birth to a single calf, and generally wait two to five years before reproducing again, although calving occurs year round. Calves remain dependent on their mothers for up to two years, nurse underwater, and begin nibbling aquatic vegetation a few weeks after birth.