(AP) -- Crews with bulldozers buried 49 pilot whales in sand dunes on an isolated northern New Zealand beach Sunday after rescuers managed to save only nine from a group that was stranded on the beach for two days.
Indigenous Maori elders chanted prayers over the carcasses before bulldozers stripped open a trench above the waterline to bury the mammals, which died despite efforts by more than 200 rescuers.
The rescuers refloated 13 of the beached whales Saturday after a mass stranding of 58 of them on remote Karikari Beach. Four of the 13 survivors later were euthanized after they beached again, bringing the overall death toll to 49.
The survivors had headed out to sea Saturday afternoon and were monitored to ensure they did not return to the beach, Conservation Department spokeswoman Carolyn Smith said. But within an hour four of them became stranded again, Smith said.
Rescuers spent two hours trying to help them, but as darkness fell officials decided to kill the distressed whales to prevent the nine survivors from being lured back by their distress calls.
The remaining nine were later observed swimming strongly and steadily back out to sea.
The full pod of pilot whales that beached Thursday night on the storm-tossed Karikari Beach were stranded for up to 12 hours before they were discovered - the reason so many died, Smith said.
On Friday, conservation department workers and trained volunteers from the Far North Whale Rescue group struggled unsuccessfully to refloat the survivors, hindered by heavy seas and wind. On Saturday they used a crane and body sling to lift and then transport them half a mile (a kilometer) to Matai Bay, a sheltered location with calmer waters.
A pod of 101 pilot whales was stranded on the same beach in 2007.
New Zealand has one of the world's highest rates of whale strandings, mainly during their migration to and from Antarctic waters.
Since 1840, the Department of Conservation has recorded more than 5,000 strandings of whales and dolphins around the New Zealand coast. Scientists have not been able to determine why whales become stranded.
Explore further: Vietnam's taste for cat leaves pets in peril