A pod of 39 pilot whales died after stranding themselves at a remote beach on New Zealand's South Island, conservation officials said Monday.

The whales, which are notorious for beaching themselves, were being monitored after they were spotted close to the shore of Golden Bay on Sunday but rangers were powerless to stop them stranding, the Department of Conservation said.

Golden Bay conservation services manager John Mason said 12 of the whales died naturally and rangers euthanized the rest after assessing they were too far up the beach to be refloated.

"We carefully weighed up the likelihood of being able to refloat them and get them safely back out to sea," he said.

"But our staff, who have extensive experience in dealing with mass whale strandings in Golden Bay, determined that due to various factors it was unlikely they could be rescued."

Mass pilot whale strandings are common in New Zealand, with scientists unclear about why the marine mammals swim ashore in large groups.

© (c) 2014 AFP