Almost 200 whales stranded on New Zealand beach

Almost 200 pilot whales stranded themselves Friday on a New Zealand beach renowned as a deathtrap for the marine mammals, conservation officials said.

At least 24 whales from the pod of 198 that beached themselves at Farewell Spit had died and rescue workers were trying to refloat the survivors, the Department of Conservation (DOC) said.

"Re-floating stranded whales is a difficult and potentially dangerous job... community group Project Jonah has 140 volunteers in the Golden Bay area who are trained to do this and we’re working alongside them," DOC spokesman Andrew Lamason said.

He said if the re-float attempt late Friday failed then the rescuers would have to wait 24 hours for another high tide before trying again.

Farewell Spit beach, at the northern tip of the South Island, has been the scene of many mass pilot whale strandings over the years.

There have been at least eight in the past decade, including two within the space of a week in January last year, although the latest stranding is one of the largest.

Pilot whales grow up to six metres (20 feet) long and are the most common species of whale in New Zealand waters.

Scientists are unclear why they strand themselves in large groups, with some speculating healthy whales beach themselves while trying to help sick or disorientated family members that are stranded.

Others believe the topography of certain places like Farewell Spit somehow scrambles the whales' sonar navigation, causing them to beach.

Once stranded, the whales are vulnerable to dehydration and sunburn until rescuers can use the high tide to move their massive weight back into deeper water.

Once refloated, the whales often simply swim back ashore and have to be euthanised.