Most of the food eaten by manatees is composed of plants that grow in freshwater and salty environments, since they are herbivores. They eat freshwater plants, such as water celery, musk grass, hyacinth, alligator weed, pickerelweed, hydrilla and water lettuce. Salt water plants eaten by manatees include marine algae, sea grasses, turtle grass, widgeon grass, shoal grass and manatee grass.
Manatees are known to eat up to 200 pounds of aquatic plants each day. They can consume food that is equal to up to 15 percent of their body weight. In Sierra Leone, manatees are known to consume planted rice. Some manatees in the Amazon are known to fast during the dry season. They can fast up to 7 months depending on the period of the dry season.
Manatees do not have front teeth for cutting food into pieces. Instead, they have a ridged pad behind the lips that is used to tear through plants, and enamel-crowned molars that are necessary for grinding food. They also have a slip on the upper lip pad to allow the sides to move independently. Manatees can comfortably feed at the surface and bottom of water, as well as in the water column.