Up to 145 pilot whales have died on a remote beach on New Zealand’s Stewart Island after becoming stranded over the weekend.

The grisly find was made by a hiker late Saturday who was camping near Mason Bay on the west coast of New Zealand’s most southern island, the Department of Conservation (DOC) said in a statement Monday.

Half of the whales had already died by the time they were found and the other half had to be euthanised.

“Sadly, the likelihood of being able to successfully re-float the remaining whales was extremely low,” the DOC’s Ren Leppens said.

The remote location, lack of nearby personnel and the whales’ deteriorating conditions meant the most humane thing to do was to euthanise the remainder of the whales which had stranded in two pods two kilometres apart. 

“However, it’s always a heart-breaking decision to make,” Leppens added.

Whale strandings are relatively common on New Zealand shores, with the DOC responding to an average of 85 incidents a year. Most of these are single animals and not large pods.

While pilot whales are prolific stranders, this behaviour is not well understood. Factors may include sickness, navigational error, geographical features, a rapidly falling tide, being chased by a predator or extreme weather.

In February 2017, more than 300 pilot whales died at the northern tip of New Zealand's South Island, in one of the biggest mass whale strandings ever recorded in the country.