Dugongs are usually seen as solitary individuals or in a group of two, although larger groups of several hundred individuals have often been recorded. The most stable and long-lasting groups appear to be mothers and calf pairs; calves suckle from their mothers for approximately 18 months (8). Dugongs can be extremely long-lived, reaching ages of 70 years or more (3). Both dugongs and manatees (Trichechus spp.) have a low metabolic rate allowing them to exist on a herbivorous diet, and consequently they usually move relatively slowly. They have pectoral mammary glands reminiscent of human breasts. These features may have caused sailors to liken them to mermaids or sirens; hence the order name of 'Sirenia' (5). Although most seagrass beds upon which dugongs feed occur at depths of 1 - 5m (4), they are known to feed at depths of up to 33 m (9). Using their flexible upper lip to rip out the whole plant, dugongs leave characteristic furrows known as 'feeding trails' on the sea floor (3). Dugongs are more closely related to elephants than the cows after which they are named, and have a particularly long large intestine to aid digestion (8).