Sydney  - Only five of the 50 whales that beached on an Australian island are likely to survive, the Tasmanian Parks and Wildlife Service said Friday.

The whales came ashore on Perkins Island, near Smithton, on Thursday and have defied frantic efforts to coax them back out into the Tasman Sea.

Parks spokeswoman Liz Wren said sandbars around Perkins Island were hampering the rescue efforts.

More than 250 whales have died in three separate strandings in Tasmania's north-west in the past two months.

Opinions differ on why strandings happen. The thousands of hours put in by nature lovers trying to refloat whales often end in disappointment when they get too weak to be saved or return to the beach after being pushed out to sea. (dpa)