Dugongs
Photo courtesy of Great Barrier Reef Marine Park Authority.
- ( TOWNSVILLE, QUEENSLAND, AUSTRALIA)
SIZE:
- HEAD TO TAIL:
- 109 (newborn) - 315 (223) cm (males)
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- 106 (newborn) - 300 (219) cm (females)
- WEIGHT:
- 20 (newborn) - 420 kg (both sexes)
- IDENTIFICATION:
- Grey to bronze above, almost white below. Readily
distinguished from dolphins by broad, rounded
upper lip, with bristles, paired nostrils, mobile paddle-like forelimbs and absence of dorsal fin.
- RECENT SYNONYMS:
- Dugong dugon, Dugong australis
- OTHER COMMON NAMES:
- Sea Cow
- STATUS:
- listed by IUCN as vulnerable to extinction
- SUBSPECIES:
- None.
- REFERENCES:
- Husar, S.L. (1978) Dugong dugon
Mammalian Species No. 88.
The American Society of
Mammologists. Marsh, H. (ed.) (1981) . TheDugong.
Proceedings of a Seminar Workshop held at James Cook
University, 8 -13 May 1979.
James Cook University, Townsville, Qld.
The Dugong is the only living herbivorous mammal that is completely marine.
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- It inhabits shallow, warm (18 deg. C or above) tropical and subtropical coastal waters of the Indian and western Pacific oceans: in Australia, its range extends around the northern coast from Shark Bay, WA, to Moreton Bay, Qld. The dugong spends most of its time in calm, sheltered, shallow nutrient-rich waters where fine bottom sediments support meadows of seagrasses on which it feeds. It occurs in clear or muddy bays, broad channels, the lee sides of coastal islands and some coral reefs.
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- The Dugong feeds almost exclusively on seagrasses, marine algae being occasionally eaten if these are scarce. All species of seagrass are browsed and there is a preference for tender new growth. In tall luxuriant stands of seagrasses, only the leaves are grazed but, where these are sparse, the entire plants, including rhizomes and roots are consumed, this destruction resulting in distinctive elongated, trail-like scars through the aquatic vegetation.
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- Adaptions for feeding include a dense, heavy skeleton which helps to keep it on the bottom while feeding; a downward deflected snout and ventrally positioned mouth; a broad, flexible, sensitive upper lip for working seagrasses into the mouth; horny pads at the anterior ends of both upper and lower jaws for grasping and possible mastication of seagrasses; flattened peg-like cheek teeth for further mastication; a very large sac-like stomach for storage of the fibrous food; and a much elongated intestine.
When undisturbed, its daily movements and activities are largely determined by tide, weather and season. Animals move in toward shores or shoals with the rising tide to feed; at low tide they rest or feed in deeper water. In calm weather they move from sheltered into exposed waters.
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- Daily movements of up to 25 km are common, and animals may move up to 100 km or more in the course of a year.
The Dugong is normally gregarious: where populations have not been recently disturbed or decimated, as in Moreton Bay and eastern Cape York, herds of several hundred animals are found. Details of social behaviour are not well known but Aboriginal hunters refer to 'whistler' Dugongs, especially large, strong old males that act as herd masters and appear to use a whistling sound to keep their herds together. Underwater chirping sounds may also contribute to social behaviour. The ear openings and eyes of a Dugong are small but it has an excellent sense of hearing and seems to have very good sight.
