Farmers of the sea: India’s dugongs must stay a conservation priority Premium

Discover the gentle giants of the sea, the dugongs, and the urgent need to protect their fading habitats.

Waving meadows of emerald grasses part as a portly shape drifts through the shallow waters. Like a blimp led astray, the creature uses its front flippers to paddle gently as it nibbles on the seagrass that makes its home. Silt stirs from the shallow seafloor, coral reefs reveal themselves in a riot of colours, with shoals of fish scurrying out of the way, and an entire ecosystem comes into view.

Meet the dugong — the farmer of the sea.

May 28 is celebrated every year as World Dugong Day. Dugongs (Dugong dugon) are the only herbivorous mammals found in India’s marine ecosystems. This gentle giant — known as the sea cow but resembling a cross between a seal and a whale — is distributed through the Indo-Pacific region. Due to their dependence on seagrass beds for habitat and food, dugongs are restricted to shallow waters, where they spend the day feeding on seagrasses of the genera Cymodocea, Halophila, Thalassia, and Halodule. They root at the base of shorter seagrass species, eating rhizomes, stems, and leaves, thus clouding the shallow waters. This is how they earned their epitaph. (Also see the addendum.)

Seagrass is low in nutrients, so dugongs feed extensively throughout the day to meet their daily requirements. They can consume 20-30 tonnes of seagrass per day, crushing leaves and stems against their horned teeth before swallowing. Unlike other marine mammals, the way they eat allows dugongs to digest cellulose, although the process wears down their teeth quickly. For this reason, dugongs rapidly regrow teeth in multiple iterations throughout their lives.

Unlike manatees, their close relatives, dugongs are more strictly marine, preferring waters a few metres deep. They are found along the Indian coastline, primarily inhabiting warm waters around the Andaman and Nicobar Islands, the Gulf of Mannar, Palk Bay, and the Gulf of Kutch. The dugong is a long-lived species, able to live up to 70 years.

Dugongs are also generally solitary or found in small mother-calf pairs. Researchers have occasionally observed small groups, but large herds — as are common in Australian waters — are rare in India.

Individuals reach reproductive maturity after only nine or ten years and can give birth at intervals of around three to five years. Due to its slow reproductive cycle, extended time to maturity, and infrequent calving, a dugong population’s maximum potential growth rate is estimated to be just about 5% per year.