Fifty-eight pilot whales died after they washed onto an isolated beach in northern New Zealand and rescue volunteers' initial efforts to refloat 15 others that survived failed Friday. A fresh attempt to save the 15 beached sea mammals - which weigh up to 3,300 pounds each - will be made early Saturday, using machinery including a crane and transporter, said Department of Conservation acting area manager Mike Davies. The 73 pilot whales probably stranded during the night on remote Karikari Beach which is why so many died before they were discovered, said the department's community relations manager, Carolyn Smith. New Zealand frequently sees several mass whale strandings around its coastline, mainly each summer as whales pass by on their migration to and from Antarctic waters. Scientists have not been able to determine why whales become stranded. A pod of 101 pilot whales stranded on the same beach in 2007. Kimberly Muncaster, chief executive of the Project Jonah whale aid group, said the 15 surviving whales were in “fairly poor condition.” About 40 people tried to refloat them at high tide on Friday. Among those helping the department were trained volunteers from the Far North Whale Rescue group. Davies said the 15 whales would not need to be sedated for Saturday's second rescue attempt using the heavy equipment as they were already in quite a docile state. “The plan at first light will be to remove the ... whales across about 1 kilometer (half a mile) of road by transporter and refloat them in (nearby) Matai Bay,” he said, where sea conditions would be easier and the bay more sheltered. New Zealand has one of the world's highest rates of whale strandings, according to the Department of Conservation. Since 1840, more than 5,000 strandings of whales and dolphins have been recorded around the New Zealand coast.