GENERAL FEEDING BEHAVIOR OF

MANATEES

Manatee digestive systems are designed to maintain a high-fiber, low-protein vegetation diet. As a result, manatees enlist hindgut fermentation, in which intestinal bacteria break down the cellulose found in plants. Moreover, manatees have very slow metabolic rates. These rates have been noted to be only 15-22% that of a similarly sized land mammal.

They can spend up to eight hours a day feeding and are able to consume nearly 10% of their body weight from this wet vegetation. Their diet consists of over sixty species of plants. In freshwater environments, this can include hydrilla (See picture below) and water hyacinth, which are invasive exotic plants to Florida. In salt water, manatees will primarily eat sea grasses. (Ripple, 1999) These could include turtle grass, manatee grass, and shoal grass. Smaller, more tender species of sea grass are consumed whole because they are easily uprooted, but manatees will usually disregard the rhizomes of tougher, larger plants when grazing. It is important to note, however, that manatees do eat things other than sea grass. In some salt water environments, they will eat mangrove leaves and seedlings.

Moreover, they have also been observed to eat the acorns of overshadowing Oak trees and accidentally, some small invertebrates. These small animals can usually be found clinging to the leaves of mangroves or blades of sea grass, and thus, are unintentionally eaten. However, this may contribute an important amount of protein to the manatee’s diet. In very rare instances, manatees have actually cleaned the flesh off of immobilized fish that had been caught in fishing nets or leftover fish in aquarium tanks. (Ripple, 1999)

Manatees consume plants by first tearing and grabbing at them with their lips, passing the food in a backwards motion, and then use their molars to chew up the material (Ripple, 1999). As an order, Sirenians were able to evolve highly modified mouthparts to assist in their feeding on plants. Because manatees have a moderately down-turned rostrum, they are able to feed on the bottom, at the surface, or in the water column, whereas dugongs are only able to feed on the bottom because their rostrums are sharply down-turned (Bowen et al., 2002). Although, manatees are more likely to consume vegetation that is submerged, rather than on the surface, because there is a greater amount found there (Marshall et al., 1998a). Furthermore, manatees have adapted the ability to use modified vibrissae, in the form of perioral bristles, in a prehensile manner during feeding (Bowen et al., 2002).