Whale stranding ‘like a plane crash’

False killer whales like this pod are not a well-known species as they live mainly in deep waters. Videos of a recent stranding of false killer whales at Māhia show they were confused and racing to the beach. Māhia has been described as “a whale trap”.Picture supplied

How a pod of false killer whales ended up stranded on a beach near Māhia this summer may never be known, marine scientist Jochen Zaeschmar says.

A pod of 44 false killer whales and one bottle-nose dolphin stranded last month at Taylor’s Bay.

Once refloated, the mammals restranded further south on a reef and had to be euthanised.

Mr Zaeschmar is a conservation biologist who started the Far Out Ocean Research Collective after initiating the New Zealand false killer whale research programme in 2005.

Far Out provides a platform for open ocean research and marine conservation and Mr Zaeschmar owns its main research vessel, the Manawanui.

“We will never fully understand why it happened,” he said of the recent pod stranding.

“The picture emerging is like a plane crash — more than one thing has to go wrong and two or three factors have to happen.”

What is known is that Māhia is “a whale trap”.

“Eighty percent of mass whale strandings in New Zealand happen at the same 10 beaches and Māhia is one of them.

“At Māhia, you have a gradually shelving soft sand beach.

“That means two things — the soft sand absorbs sonar signals sent by the whales and the low angle incline deflects rather than reflects the sonar.

“It is like when you are on a boat and the radar does not pick up a sandbar; the whales think they are swimming in deep water.

“The cliffs give off a big echo and the beach does not.”

Not much is known about false killer whales, which are often mistaken for pilot whales.

“They have a matriarchal society like other oceanic species, with strong family structures similar to pilot whales and sperm whales.

“Videos of the stranding show they were confused and racing to the beach. It could have been a distress call.

“They all stranded tightly and were super-protective, with the younger mammals in the middle — just  as an interesting observation.”

Mr Zaeschmar said he had not seen this pod before and it was not one of the pods he had studied.

“These were open ocean whales. We could tell by the fins that we did not know the individuals.”

It was not uncommon to see them at this time of year in waters of 10 metres or less, hunting for snapper, kahawai and kingfish, he said.

A video of a pod back in 2018 showed they used the area for feeding — coming in with the warm water like game fish such as marlin and tuna.

“Locals I spoke with were saying they saw lots of kingfish in the area and that may have drawn them in.”

Department of Conservation Tairāwhiti operations manager Matt Tong said the reason for euthanising the animals was their welfare and the heightened risk of them restranding.