stranded whales

A recent stranding on remote New Zealand islands left nearly 500 pilot whales dead. Scientists still don't know for sure why the events, also known as beachings, occur, but they have some ideas.

The whales beached themselves on the Chatham Islands, about 500 miles east of New Zealand's main islands. None of the whales could be refloated and all either died naturally or were euthanized.

Australian wildlife authorities are investigating the deaths of the whales, which were discovered Monday on Tasmania's King Island, off the southeastern coast.

"While they are still alive and in water, there is certainly hope for them, but as time goes on, they become more fatigued and their chance of survival reduces," said a government wildlife official.

Video of the area shows large groups of pilot whales stuck on sandbars, trying fruitlessly to free themselves. An estimated 25 whales have already died.

Answers remain elusive for the country's Department of Conservation, which believes these incidents are not related. In the latest one, more than 50 pilot whales died in the remote Chatham Islands.

A hiker reported the mass stranding Saturday. By the time officials could reach the marine mammals, half were dead — and the rest were in such dire condition, they had to be euthanized.

After two mass strandings left over 650 pilot whales washed ashore at a remote beach and hundreds died, volunteer rescuers finally got some good news: A large pod swam back to sea overnight.

Volunteers gathered early to send some 100 surviving whales back to sea, after one of the worst mass strandings in New Zealand's history. But just hours later, a new large pod washed ashore nearby.