The dugong is a large herbivorous marine mammal with paddle-like forelimbs and no hind limbs or dorsal fin. Its tail is broad, triangular in shape, and horizontally flattened, which it moves up and down to swim. Adult dugongs have a head and body length of up to 3.3 m, and weigh up to 570 kg. Adults are grey-brown in colour, and older animals may have white scars on their backs. Its ears are small bilateral openings. The dugong has nostrils near the top of its snout and surfaces only to breathe. The tusks of mature males, and some old females, erupt on either side of the upper jaw, but do not extend beyond the end of the premaxilla. The dugong has two mammary glands, each opening via a single teat situated in the ‘armpit’ or axilla.
Government evidence of impact of climate change:
Australian Government Department of Agriculture, Water and the Environment, Species Profile and Threats Database, Dugong Dugong
These fluctuations apparently track major changes in the status of the dugong s food supply; which is subject to episodic (a series of separate events) diebacks that are often associated with extreme climatic events; including exceptionally high rainfall and cyclones (Johannes and MacFarlane 1991 Preen and Marsh 1995 Poiner and Peterkin 1996 Marsh and Kwan 2008 Marsh et al. 2011a Sobtzick et al. 2012).
However; the aerial survey estimates in 2011 after the extreme weather events of the summer of 2010 11 were the lowest since the surveys began in 1986 (Sobtzick et al. 2012; 2015b).
These fluctuations are partially attributable to dugongs moving between bays or from shallow to deeper water within bays; especially after seagrass is lost as a result of extreme weather events; but there are indications of a declining trend in the southern Great Barrier Region; although whether this is the result of temporary emigration is not known.