Dugongs are primary consumers and the only completely herbivorous marine mammals. They consume seagrass, particularly of the families Potamogetonaceae and Hydrocharitaceae in the genera Halophila and Halodule. They prefer seagrasses that are low in fiber, high in available nitrogen, and are easily digestible for better nutrient absorption. Their long intestine aids the digestion of seagrass. They also have a low metabolism. When seagrass is scarce, dugongs also eat marine algae. They are speculated to supplement their diet with invertebrates such as polychaete worms, shellfish and sea squirts which live in seagrasses.
Dugongs use their flexible upper lip to rip up entire seagrass plants. If the entire plant cannot be uprooted, they rip off leaves. Their grazing leaves distinctive furrows in the seagrass beds that can be detected from the surface. To be supported properly by their environment for a year, dugongs require a territory with approximately 0.4 ha of seagrass. This area varies with individual and the extent of their movement, the amount of seagrass detected on the sea floor compared to what it actually ingested, the yearly productivities of seagrass, and the rates of re-growth of seagrass.
Animal Foods: aquatic or marine worms; other marine invertebrates
Plant Foods: algae; macroalgae
Primary Diet: herbivore (Folivore , Eats sap or other plant foods)