Satellite tracking and aerial surveys allow scientists to find out where dugongs travel.

• James Cook University researchers satellite tracked 70 dugongs to determine their patterns of movement:
• Surveys took place on the east coast of Queensland and Gulf of Carpentaria, Australia, between 1986 and 2004
• 26 moved over relatively small distances of less than 15 km
• 44 made large-scale movements (between 15 km and 560 km from their capture sites)
• Dugongs normally confine their activities to what is known as “home ranges”, which were from 1.6 to 128 km²
• Dugongs rarely travel far from the coast (mean maximum distance = 12.8 km)
• Large-scale dugong movements of more than 15 km occurred by both males and females of all size and age classes, including cows with calves
• Aerial surveys conducted over a series of years have provided further evidence of large-scale movements as numbers fluctuate throughout the Torres Strait, Queensland, Northern Territory and Western Australia
• Dugongs are at high risk of capture in bottom set gill nets because they make repeated deep dives when travelling rather than just remaining on the surface
• It is possible mothers transfer their spatial knowledge of quality seagrass locations to their calves.

Why might dugongs travel long distances (greater than 15km)?

• Loss of seagrass habitat – resulting from events such as cyclones, floods and outbreaks of toxic algae
• Reduction in food quality – animals may remain in the area or move to find seagrass elsewhere
• Social triggers – may cause them to bypass known dugong habitats - males may be following fertile females at mating time or competition may exclude lower-ranked animals from occupying certain seagrass habitats
• Low water temperatures – when water temperature drops below about 17 to 18 °C, dugongs tend to move to warmer waters.
  

Why do dugongs undertake small-scale dugong movements (<15km)?

• Tidal movements – dugongs feeding on shallow seagrass may move short distances in response to tidal movements
• Daily commuting – to forage among intertidal seagrass beds close to the shore during periods of high tide
• Staying close to core habitat – dugongs express high site fidelity to core areas of high quality seagrass habitat, which they use intensively within small home ranges.

An example of small-scale movements: Wunai’s Movements in the central Great Barrier Reef

Map showing movements of ‘Wunai’, a 1.9 m male. Each red dot represents a separate location fix from the GPS tag attached to the animal for a month. The close proximity to the shore and small home range of the movements is typical of all tracked dugongs (© Topographic map courtesy of the Australian Hydrographic Service).