The dugongs of Mantanani

Story and photos by Gillian Elliott

gillian_elliott_dugong1Dugongs have been fabled as sirens, the mermaids of the sea and this is reflected in the name of their scientific order, the Sirenia. Sirens were the fabled maidens in the times of ancient Greeks. In Homer’s epic story, Odysseus and his crew were said to have tied themselves to the mast of their ship to avoid ruin. The sirens would sing their magical songs luring sailors too close to the rocks on which they rested and, in this way, many ships and their crews met a watery grave.

In reality, sirenians are very different from the seductive maidens of lore. Dugongs are large weighty animals with a pig-like snout covered with whiskers and they communicate by birdlike whistles and chirps.

On Mantanani Islands (06º 42N, 116º 20E) in Sabah we have been lucky enough to sight several dugongs on a regular basis and even to observe them in close proximity. Dugongs are mammals and thus must breathe air at regular intervals with the time between breaths about 5 minutes. This surfacing behaviour provides us with the opportunity to spot the dugongs as they feed in the bay; a brief glimpse of the top of the dugong’s head and the sound of its intake of breath.

Habitat

There are three islands in the Mantanani group and they are located in the South China Sea off the coastline of Kota Belud, 80km north of Kota Kinabalu. The sheltered bays around the Mantanani Islands seem to provide the ideal habitats for dugongs. Sea grass beds are found on shallow sandy areas within the encircling fringing reef of the islands. A small human population has caused minimum pollution and there is little noisy boat traffic

Dugongs are agile and can move fast despite their large body size and a mature adult may weigh up to 350kg. Thrusts of the dolphin-like tail provide propulsion and top speeds of 25km/hr can be attained. The usual cruising speed is 10km/hr and the dugong may travel for hundreds of kilometres over just a few days. The dugong has pectoral flippers for steering and braking, and also for sculling to keep the animal’s head above water when it breathes in choppy seas.

Dugongs are usually resting in deeper water during daylight hours and come into shallow water to play and feed at sunset and night. The dugongs are usually seen between 4pm and 6pm.

Feeding

Dugongs are known also as sea cows due to their vegetarian nature. While they may consume over 15 different species of sea grasses, their favourites (which are found in abundance on Mantanani) are the species of the genera Halodule and Halophila.

Dugongs consume large quantities of sea grass in one day: a fully-grown dugong will eat up to 35kg daily, one-tenth of its body weight. As dugongs feed they plough furrows through the sea grass beds and leave meandering feeding trails of startlingly white sand amongst the green of the sea grass bed.

The rhizomes of the grasses are high in protein and low in fibre and thus the most desired part for consumption. A particular dugong may feed in several different areas on a rotational basis, allowing sea grass beds to regenerate before the next grazing episode.

Behaviour

On Mantanani we have seen a total of three dugongs: a mother (3m long) with her young calf and a young male (1.5m long) that seems curious in humans. When we first spotted the dugongs in October 2000, the young male in particular often approached a diver or snorkeller, did a quick circle of us, and then headed off. Presumably the human visitor to the aquatic realm was not particularly interesting at first, and the bubbles produced by a SCUBA diver exhaling seemed to frighten him off.

Recently this juvenile male – we can recognise him by a small tear in the tail fluke – has become rather inquisitive towards snorkellers and he is actually approaching us seemingly to play.

Noisy boat engines are a deterrent to the dugong but a quiet snorkeller or swimmer is sometimes circled repeatedly just out of arm’s reach. Perhaps this juvenile is interested in humans for social contact since dugongs are social animals to some extent.

Scarring observed on his back surface may be due to fighting or mating with his own kind and this suggests that there may be more dugongs in the area.

Population

gillian_elliott_dugong2There are thought to be about 100,000 dugongs in the world and this is a pitiful fraction of their former population. Aerial surveys carried out by Universiti Malaysia Sabah three years ago counted a total of 20 dugongs in local waters and this data was projected to an estimate of 100-200 individuals in the area.

However, such surveys are very expensive and are complicated by the large ranges frequented by some dugongs. They may travel hundreds of kilometres within a few days and thus the same animals could be recounted on subsequent days of the survey if their movement happens to coincide with that of the survey area. Conversely, such movements could result in the failure to observe the dugong as it moves constantly away from the areas being surveyed.

Conservation of species

Worldwide, dugongs are facing the threat of extinction and it is likely that this is also the case in Sabah. In the World Conservation Union Red Data book, dugongs are listed as “vulnerable to extinction” and the international trade in dugong artifacts has been prohibited in the Convention on International Trade in Endangered Species (CITES). Locally in Sabah, the Fauna and Flora Conservation Ordinance has awarded the dugong “totally protected” status.

The threat to dugongs

Dugongs face many threats and some are due to natural phenomena although the greatest and increasing threats are due to human activities. Sharks, crocodiles and killer whales, prey upon dugongs and sometimes dugongs may be fatally stranded on beaches, especially in bad weather.

Humans have long hunted dugongs, and their meat is considered a delicacy. The blubber can be used in medicines and cooking, the tough skin used for shields and other leather goods, while the heavy bones and tusks are carved into lucky charms. The tears of the dugong are believed to have aphrodisiacal qualities.

An increase in numbers and speed of motorised boats would provide a potential hazard, especially if there heavy boat traffic is in shallow coastal areas. Illegal fishing methods such as dynamite fishing are also dangerous for dugongs. While dugongs would rarely be bombed on purpose, an individual too close to the bomb blast would become an accidental victim.

Trawling and gill netting are two legal fishing methods that may entrap dugongs and cause them to drown before the fisherman collects his catch. The dugong on display at the State Museum in Kota Kinabalu was discovered drowned by a Kudat fisherman when he lifted his nets one morning in 1984.

Increasing coastal developments, land reclamation and the use of river mouths as ports have damaged former dugong habitats. Furthermore, pollution associated with human developments such as super-eutrophication of water bodies has damaged the sea grass beds on which dugongs rely. In other countries, toxic heavy metal compounds have been found in increasing quantities in dugongs that underwent autopsies.

What does the future hold?

gillian_elliott_dugong3While the future for the dugong in Sabah, as in most countries in the Pacific rim, may look bleak, there is some hope for the future. The dugong has a very slow reproduction rate and it is likely that a 5% population increase per year is the maximum that can be hoped for.

It is difficult to enforce conservation policies in the state due to its extensive and isolated coastline, the numerous islands, and the population of 20,000 fishermen, most of whom live close to the poverty line and have no conservation priorities.

Sabah’s global status as a leader in eco-tourism may be the saving factor for the dugong. The influx of visitors to the state each year is bringing financial benefits to areas where once all livelihood was generated from the daily catch from the sea.

Today, more people are being employed in the tourism industry and realising the benefits of preserving their natural resources for the future. SCUBA diving and beach resorts are increasing on the islands and coastline of Sabah, as the world realises the richness and diversity of the seas in the region.

For the present, the dugongs of Mantanani are to be cherished and all possible efforts made to protect them from the destructive forces of man. The information provided by the study of the behaviours and feeding ranges of these animals may provide the basis for effective conservation measures. We hope these dugongs will continue to frequent the islands of Mantanani, coexisting with the fisherfolk and visitors to the island and even increase in numbers.

Gillian Elliott is a marine biologist working at Mantanani Resort and she has been lucky enough to encounter the dugongs in afternoon snorkels in front of the resort. One of her job duties is to explore the reef around the islands and brief resort guests about the wonders of the underwater world.

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