Learn about Dugong

The dugong sports a submarine-shaped body interrupted only by a pair of flat forelimbs and terminating at a short-snouted head. Unlike their paddle-tailed manatee cousins, dugongs propel themselves with dolphin-like flukes. Highly specialised hearing compensates for their limited eyesight allowing them to communicate at frequencies below human range. Adults reach lengths between 2.5 and 3 meters, usually weighing just over 400 kg.

Satisfyingly consistent with their behaviour and appearance, dugongs enjoy long lives of gradual development. Upon reaching sexual maturity at 10 years old, females produce a single calf every 2.5 to 5 years following a fourteen-month gestation period. Newborn calves are 1 – 1.5 meters in length and weigh about 25-30 kg and remain dependent on their mother’s milk for eighteen months. They have been known to reach 70 years of age!

The dugong is an obligate bottom feeder (grazer), with an ideally suited muzzle with flexible lips which is ideally built for tearing up the sea grasses on which it feeds on; it eats vascular sea grasses that are comparable to terrestrial grasses; the roots being the most nutritious. It may feed on brown algae in times of critical food shortage, but studies have shown that algal material is not readily digested. Ongoing research in Sri Lanka has shown that the dugongs in Sri Lankan waters are partial to certain species of sea grasses like Halophila spp. and Halodula spp. which are high in nutrients.

The dugong historically had a wide range, which spanned at least 37 countries from East Africa to the West coast of Australia; they specially inhabit shallow waters around islands, which promote the growth of “sea grass”.

Though once widely distributed, it is now restricted to coastal waters of parts of the Indian and Pacific Oceans, largely due to being overhunted for the meat, hide and especially oil. The dugong’s historic distribution is believed to have been broadly coincident with the tropical Indo-Pacific distribution of its food plants, namely the Phanerogamous plants of the families Potamogetonaceae and Hydrochritaceae, more commonly known as “sea grass”. The largest surviving populations are found in Northern Australian waters and the second largest in the Arabian Gulf. Elsewhere, populations are small and fragmented and in some areas, such as Mauritius, the Maldives and parts of Cambodia and Laos, dugong have already disappeared (Marsh et al., 2001).

Dugongs being specialist herbivores, their distribution within its existing range is mainly confined to sea grass meadows, which occur in calm and shallow coastal areas, such as bays and lagoons. As such the only records in Sri Lanka, come from the North Western province i.e. Puttalam lagoon, Kalpitiya, Mannar, Jaffna and sporadically in Trincomalee and Batticaloa according to available records. However, ongoing research has shown that the dugong has had a much wider distribution trend in Sri Lanka, which has stretched up to the south of the island. They have been also observed in waters farther offshore in areas where the continental shelf is wide, shallow and protected. It is generally acknowledges that the population has drastically depleted in recent years. Anecdotal reports state that “It is rare nowadays for more than one specimen to be taken, whereas formerly in the Gulf of Mannar they were found in their myriads, numbers running in to their hundreds”.

Recent surveys show that the remaining populations of dugongs in our waters are confined mainly to the North Western part of the Island with a scattered population on the East coast of the Island.

The dugong, being a proclaimed protected species in Sri Lanka under the Fauna and Flora Protection Ordinance (FFPO) enjoys very little actual protection in its fragile and localised habitat.

Dugongs are one of the most critically endangered large mammals of Sri Lanka, if not in the world. They are vulnerable to adverse human activity in their habitats due to their life history and their dependence on sea grasses which are restricted to coastal habitats. These areas are often under pressure from anthropogenic activities such as pollution, habitat degradation and destruction, as well as incidental capture during fishing operations and dynamite fishing in the North Western and Eastern coast. These pressures have resulted in drastic reduction of their population. If this species has any chance of survival in Sri Lankan waters, action is required urgently to protect critical habitats such as feeding pastures and calving grounds and to mitigate the threats, if addressed immediately, it may be possible to bring dugongs back from the brink of extinction in Sri Lankan waters and ensure their place in our Country’s rich and diverse natural heritage.