Manatees may live as long as 60 years based on analysis of growth layers in the ear bones (Marmontel et al. 1996). Perinatal survival are rates low, with half of all carcasses recovered in Florida between 1976 - 1991 aged from 0 - 2 years of age (Marmontel et al. 1997). Survival rates increase steadily to Age 4, then remain constant (89.9%) from approximately Age 4-25 years of age (Marmontel et al. 1997).Newborns average 1.2 - 1.4 m in length (4 - 4.5 ft.) and 30 kg (66 lbs.) (O'Dell 1981). Maximum adult size is approximately 4.6 m (15 ft.) and 1,620 kg (3,570 lbs.), with females tending to grow larger than males of the same age (Rathbun et al. 1990).
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