As many as 145 pilot whales died on a New Zealand island this weekend after they were left stranded on a beach.

A hiker walking along the beach discovered two pods about 1.2 miles apart at Mason’s Bay on Stewart Island, also known as Rakiura. Conservation workers arrived at the grim scene and discovered 75 of the whales were already dead. They decided to euthanize the remaining stranded whales because of the difficulty of accessing the remote location.

“Sadly, the likelihood of being able to successfully re-float the remaining whales was extremely low. The remote location, lack of nearby personnel and the whales’ deteriorating condition meant the most humane thing to do was to euthanize,” said Ren Leppens, Raikura operations manager of New Zealand’s Department of Conservation. “However, it’s always a heart-breaking decision to make.”

Leppens said the whales were half buried in sand and not in good health, indicating they had been there for perhaps a day before they were found. He said staff shot the whales and the carcasses would be left where they were for nature to take its course.

In an unrelated event, 12 pygmy killer whales were discovered stranded Sunday at Ninety Mile Beach on the North Island, nonprofit organization Project Jonah New Zealand said in a Facebook post. The organization said eight of the whales were alive and being moved to Rarawa Beach on the east coast where it was hoped they could be re-floated.

Whale strandings are not uncommon in New Zealand, but do not often happen in pods, the Department of Conservation said in a news release. About 85 whale strandings are reported yearly, with most of them involving a single animal.

Several factors can cause strandings, such as the whales trying to escape predators, falling ill or navigating incorrectly.

The Associated Press contributed to this report.