The sperm whales washed up on Ripiro Beach
© DoC
The sperm whales washed up on Ripiro Beach and were currently being harvested by local iwi. Photo / DoC
Three male sperm whales stranded on a Northland beach have all died.

The Department of Conservation today said the whales stranded on Ripiro Beach on the Poutu Peninsula near Dargaville on Monday night.

Spokeswoman Abigail Monteith said a member of the public found the whales and notified the department.

Staff monitored them overnight but they died on Tuesday morning.

Local iwi were now in the process of flensing - or harvesting - the bones. They would then be buried.

The Department of Conservation's Kauri Coast acting operations manager Stephanie Hayes asked the public to stay away from the site until the burial is complete.

"We are working in collaboration with Waikaretu Marae and Te Uri o Hau environs. Our main focus now is ensuring the safety of the public and the burial of the whales."

Te Uri o Hau Waikaretu Marae spokesman kaitiaki Colin French said: "We are starting a flensing process working with our whānaunga Ngāti Wai and Te Roroa."

The cause of death of the three whales is unknown.

Meanwhile, Monteith said the stranding wasn't unusual for either the place or time of year; there were approximately 85 strandings annually.

One of the dead sperm whales on Ripiro Beach, near Dargaville.
© DoC
One of the dead sperm whales on Ripiro Beach, near Dargaville.
Massey University professor Karen Stockin said the whales likely formed "part of a bachelor pod" of whales.

They measured in length from 14m to 17m and based on international data were categorised as adult males.

Iwi, DoC and Massey researchers were taking tissue samples and data.

Stockin said there had been more than 270 sperm whale strandings in New Zealand.

That included more than 250 single whales and 24 mass strandings, including Monday night's, ranging from 2 to 72 individuals.

Mass strandings have been recorded on mainland as well as offshore islands including the Kermadecs and Chathams since 1870s.

Most involved male whales although female pods had also been reported, predominantly in the North Island.

As for timings of the strandings, Stockin said they had been through all season however there was a "slight bias" to cold months.

"The most recent largest mass stranding was in 2018 when 13 male sperm whales stranded in end of May in the South Taranaki Bight," she said.

A review of sperm whale mass strandings in NZ by Massey researchers is currently being peer reviewed.