Dugongs are large, gentle marine mammals found in warm coastal waters across the Indo-Pacific region. Often referred to as “sea cows,” they are almost exclusively herbivorous, relying predominantly on seagrasses as their primary food source.
Specialized Diet: The Seagrass Grazer
Seagrasses are not seaweeds; they are flowering plants that grow in marine environments, forming underwater meadows that provide the bulk of the dugong’s nutritional requirements. Dugongs consume various species of seagrass, preferring softer, more digestible types like Halophila and Halodule, which are younger and less fibrous. This selective feeding helps promote the growth of these faster-growing species. Seagrass forms over 90% of a dugong’s diet, making dugongs one of the most specialized marine herbivores. The presence of thriving dugong populations often indicates the health of the surrounding seagrass ecosystems.
Feeding Habits and Preferences
Dugongs possess unique anatomical adaptations that facilitate their specialized grazing. They use a muscular, downward-pointing snout and bristly mouth to forage along the seabed. These features allow them to effectively uproot entire seagrass plants, including the nutrient-rich rhizomes, or graze on the leaves. Their poor eyesight means they rely on their sense of smell and the sensitive bristles on their snouts to locate food.
As dugongs feed, they often leave distinct foraging trails or furrows in seagrass beds, indicating their presence. An adult dugong can consume up to 30 to 40 kilograms (66 to 88 pounds) of plant material daily.
Dugongs spend much of their time feeding continuously to meet their energetic demands. Their grazing provides sustenance and influences the structure and health of seagrass meadows. They help maintain these habitats by promoting the growth of certain seagrass species and stabilizing sediments.
Dietary Adaptations and Environmental Influences
While dugongs are highly specialized seagrass consumers, occasional dietary variations can occur. When preferred seagrass beds are depleted or scarce, dugongs may opportunistically consume other marine vegetation, including certain types of algae.
Dugongs have also been observed to ingest small invertebrates such as jellyfish, sea squirts, or shellfish. These occurrences are infrequent and do not constitute a substantial portion of their overall diet.
Environmental factors significantly influence dugong diets and foraging behaviors. Events like severe storms or human activities, such as coastal development and pollution, can damage or deplete seagrass meadows. When their primary food source diminishes, dugongs are compelled to seek less ideal food options or relocate to new areas in search of healthy seagrass beds.