The deaths of 200 whales in mass strandings in New Zealand over the last week has not alarmed whale experts.
Fifty-one pilot whales died in the Chatham Islands on Thursday night, less than a week after a stranding on Stewart Island, which left 145 dead and another in Northland, in which five pygmy sperm whales had to be euthanised.
Associate Professor Rochelle Constantine from Auckland University said this was "a blip" but nothing out of the ordinary.
"We've got a little cluster of them at the moment, but we do have a lot of strandings in New Zealand, upward of 80 or 90 a year and sometimes more."
New Zealand had a lot of whale strandings because it was "a global hotspot" for whales and dolphins, with half the known species found in its waters, Dr Constantine said.
The Chathams was a particularly bad area for strandings, she said, with piles of whale bones on many beaches evidence that strandings had been happening for hundreds of years.
Whales became stranded for many different reasons: sometimes they were sick or disorientated, or got caught by the turning tide.