LONG-DISTANCE DUGONGS HOLIDAY IN WARMER WATERS

28 October 2003

Dugongs are long-distance swimmers, and can travel hundreds of kilometres in search of sweeter seagrass beds and warmer waters.

CRC Reef PhD student Mr James Sheppard from James Cook University followed the movements of seven dugongs for two months, using satellite tracking devices and dive data loggers. The dugongs were tagged in Hervey Bay, part of the traditional sea country of the Badtjala people, and were given traditional names.

“Some dugongs travel extremely long distances. One large male dugong called ‘Bum'kaman’, the Badtjala word for ‘return’, swam 300 kilometres north from Hervey Bay to Great Keppel Island, where he stayed for just over a week, before returning to Hervey Bay,” said Mr Sheppard.

“Another male dugong, ‘Wun’ai’, meaning ‘leave’, headed north to Port Clinton, averaging 45 kilometres a day over eight days. He rested there for a few days before moving on to Clairview, south of Mackay – 500 kilometres north of the tagging point.”

“Such wide roaming patterns suggest that dugong populations are mobile and linked. So, it is important to realise that the dugong population in each bay is not isolated,” he said.

“We also discovered what seems to be a wintering ground for dugongs at the tip of Fraser Island. Dugongs are sensitive to the cold, and could be attracted by warm waters from the tropics that flow into this area with the East Australian Current. Although this is a sandy place with hardly any seagrass and many sharks, four of the seven dugongs that we tracked visited several times, swimming over 70 kilometres across the Bay from seagrass beds at Burrum Heads. As sea temperature started to rise at the end of the winter, the dugongs stopped visiting this area,” said Mr Sheppard.

Dive data loggers show that while dugongs spend about 70 per cent of their time about 3m from the surface, they make long trips in a series of deep dives, up to 37m deep. This information will help managers to ensure that fishing and shark nets are placed in depths that minimise threats to travelling dugongs, as well as dugongs feeding near the surface.

The researchers are studying whether temperature and seagrass quality are linked to dugong roaming patterns. An understanding of their foraging and travel habits will help managers to protect areas important to dugongs.

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Or contact:
Mr James Sheppard, CRC Reef and JCU, 07 4781 5824 or 0421 431 355, email james.sheppard@jcu.edu.au
Ms Chloe Lucas, Media Liaison, CRC Reef, 07 4729 8450 or 0408 884 521, chloe.lucas@crcreef.com