The Conservation Department said hikers found the whales stranded Sunday on a remote beach at Stewart Island, off New Zealand's southern tip.
The department said in a statement that officials flew to the site and found that the whales were either dead or dying. The animals were well up the beach. With the tide receding there was no way of keeping the animals alive until more rescuers could arrive, so the animals were killed to prevent further suffering.
Whale strandings are commonplace in New Zealand. Last month 24 pilot whales died after stranding in the North Island.