The Last Sea Cows
In the shallow, warm waters of Koddiyar Bay, a small population of dugongs (Dugong dugon) survives. These slow-moving marine mammals are the only strictly herbivorous marine mammals in the world. An adult can grow up to three meters long and weigh as much as 400 kilograms. Despite their streamlined bodies, they are not related to whales or dolphins; their closest living relative is the elephant. The species is the last of the once-diverse family Dugongidae, after its closest relative, Steller's sea cow, was hunted to extinction in the 18th century.
Dugongs have a slow reproductive rate, which makes their populations especially vulnerable. Females are not sexually mature until they are at least six to ten years old and give birth to a single calf only once every 2.5 to 7 years. The gestation period lasts for about 13 to 15 months. A newborn calf stays with its mother for around 18 months, sometimes seen riding on her back. With a potential lifespan of 70 years, a female may only give birth a few times. This slow rate of population growth means that the loss of even a few individuals can have an impact on the small Koddiyar Bay group.
An Ecosystem of Seagrass
The existence of dugongs in Koddiyar Bay is entirely dependent on the health of its seagrass meadows. Often called "sea cows," these animals graze on underwater grasses, consuming up to 30 or 40 kilograms of seagrass daily. Their sharply downturned snouts are covered in sensitive bristles, which they use to find and uproot entire seagrass plants from the seabed, leaving distinctive feeding trails behind. Stomach content analysis of dugongs in Sri Lanka shows a preference for nutrient-rich seagrass species like Halophila and Halodule. They specifically target the roots, or rhizomes, which are the most nutritious part of the plant.
This grazing helps the health of the coastal ecosystem. By feeding on the seagrass, dugongs help maintain the structure and diversity of the meadows. Healthy seagrass beds are essential for filtering pollutants, maintaining water quality, and providing shelter for many other marine species. The seagrass meadows in Sri Lanka's Gulf of Mannar and Palk Bay are some of the most extensive in the region. These habitats are threatened by coastal development, pollution, and destructive fishing practices like bottom trawling.
The dugongs of Sri Lanka are legally protected under the Fauna and Flora Protection Ordinance, but enforcement is difficult. The primary threats to the remaining population are anthropogenic. Accidental entanglement in fishing gear, particularly gillnets, is a major cause of death. Boat strikes and illegal blast fishing also claim lives. Conservation projects in Sri Lanka are focused on mapping seagrass habitats, raising community awareness, and working with local fishers to mitigate bycatch.