Stranded Whales
© SuppliedWhales stranded on Stewart Island.

Time, hot dry conditions and a pending storm warning beat any attempts to save a large pod of pilot whales that beached themselves on Stewart Island.

The 107-strong pod was discovered by two trampers on Saturday.

Department of Conservation(DoC) biodiversity manager Brent Beavan says it took them several hours before they could raise the alarm.

Beavan says when DoC staff reached the whales, with about half their number still alive, they were stranded high up on the beach with the tide going out.

He said they were quickly aware that it would be at least 10 to 12 hours before any attempt could be made to re float them.

There was little hope of keeping the animals alive with only five DoC staff available, Beaven said.

He said given the conditions and with a storm warning in place, the decision was made to euthanise them.

"Euthanasia is a difficult decision but is made purely for the welfare of the animal involved - to prevent it from prolonged suffering," Roberts said.

The whales will be left to decompose naturally on the beach due to the remoteness of the site.