At least 31 pilot whales have died after a mass stranding at a New Zealand beach known to be a notorious spot for whale deaths.

Wildlife officials said the pod was first spotted on Thursday, beached across several kilometres of Farwell Spit on the South Island.

On Friday, rescuers managed to refloat five whales who had survived the night.

This just the latest in mass strandings at Farewell Spit, the northernmost tip of New Zealand's South Island.

"While this event is unfortunate, whale strandings are a natural phenomenon," a representative from the Department of Conservation told the BBC.

Earlier, officials had warned: "This is a stressful time for the whales after their time spent stranded yesterday and this morning."

It is not fully understood why whales became stranded but pilot whales are known to be more prone to getting beached. They are not considered endangered, although exact population numbers are not known.

Image source, DEPARTMENT OF CONSERVATION

Image caption,

Farewell Spit has been dubbed a 'death trap' for whales in the area

Farewell Spit, a 26km (16 mile) hook of sand that protrudes into the sea, has been a frequent site of strandings, although scientists are unclear why.One theory is that the spit creates a shallow seabed in the bay which then confuses the whales' sonar navigation systems.

The Department of Conservation said the cause of the most recent stranding "is not known" but noting that the spit forms extensive, kilometres-wide sand flats.

Image source, DEPARTMENT OF CONSERVATION

Image caption,

A rescuer pouring water over a whale in a bid to keep it alive

Last year, rescuers were able to save 28 long-finned pilot whales of a pod of about 50 who had stranded on the beach, but the rest died.

The worst stranding occurred in February 2017, when almost 700 whales beached, resulting in 250 deaths. The area has seen at least 11 pilot whale strandings in the past 15 years.

Media caption,

Volunteers helped push 28 whales back into the water at a similar stranding in 2021 at Farewell Spit