SYDNEY, Nov 24 (Reuters) - Australian wildlife officials were using satellite tracking on Monday to monitor a group of 11 pilot whales returned to the sea after a mass stranding on the island state of Tasmania.

The whales were the only ones from a group of 64 long-finned pilot whales that survived the mass stranding on Saturday.

Global Positioning System (GPS) devices were attached to five whales, a mix of adult and juvenile whales, and authorities said the surviving pod was swimming strongly away from land.

"These units have told us that the animals did all join up again even though they were released in a three hour period and their survival prospects are very good." Rosemary Gales from Tasmania's Department of Primary Industries told local media.

The whales were found stranded on Saturday along a stretch of Anthony's Beach at Stanley on Tasmania's northwest coast, a site where repeated strandings have occurred in the past. Around one-third of them were juveniles.

On Sunday, rescuers released 11 surviving whales into the ocean after day-long effort which involved relocating them by road to another beach.

Gales said it was the first time GPS devices have been used to track whales after a stranding in Australia.

Pilot whales are among the smaller whales, typically up to about five metres in length and dark with a grey underbelly.

Environmentalists said the chances of whales surviving a mass strading were usually low, but the relatively small size of the pilot whales may have helped rescuers save them.

Mass strandings of whales occur periodically in Australia and New Zealand for reasons that are not entirely understood. Theories include disturbance of echo-location, possibly by interference from sound produced by human activities at sea, (Reporting by Michael Perry; Editing by Sanjeev Miglani)

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