They eat 100 pounds of food each day which equals two or three bath tubs full of salad. Because plants are a relatively poor source of energy and nutrients, manatees must consume up to one-quarter of their body weight per day to obtain adequate nourishment. Manatees are very slow animals which is a result of their low metabolic rate. In South America, many of the floating mats of grasses found in rivers contain silica. Silica causes rapid wearing of the teeth.
Manatees have an unusual adaption which minimizes the impact of wear.
Rows of worn teeth are shed at the front of the jaw and replaced at the back throughout the manatees life. When humans do anything that may ruin our teeth we're in trouble because after we loose our baby set, we only have one more set left for the rest of our lives. But then we can always buy dentures, which in my opinion doesn't sound like fun. The manatee reproductive maturity is not reached until the age of four to eight years old. They have a very low reproductive rate.