Ranges of body weight and size observed are 7.5–346.5 kg and 76.0 –255.5 cm for captive males, 8.1–379.5 kg and 71.0–266.5 cm for captive females, and 120.0–270.0 kg and 162.0 –230.0 cm for free-ranging manatees, respectively.[8] The maximum actual Amazonian manatee weight reported is 379.5 kg.[8] Calves of the species are born weighing 10–15 kg and 85 –105 cm long.[8] The Amazonian Manatees increase in length approximately 1.6-2.0 mm per day. This length is measured along the curvature of the body so absolute length can differ between individuals. As calves, they gain an average of 1 kilogram per
