13 Jan 2021

Blue whale study finds special New Zealand connection

From Summer Times, 11:30 am on 13 January 2021

A new study tracking the movement of the world's largest mammal has found a special New Zealand connection.

A blue whale mother-calf pair surfaces off the South Taranaki bight.

 A blue whale mother-calf pair surfaces off the South Taranaki bight. Photo: Supplied/ Kristin Hodge

By using hydrophones, underwater microphones to you and me, researchers from Auckland University and NIWA pooled international resources to understand how Antarctic Blue Whales move around the Pacific Ocean.

One of the researchers tracking these giants was Associate Professor Rochelle Constantine. She tells Summer Times they laid hydrophones throughout central New Zealand, including the Cook Strait with the idea to record all sounds in that space.

“Within the study, we collected data on all different kinds of whales, but this particular study focused on the blue whales that pass through New Zealand waters.”

The hydrophones were deployed for around six months each with the hope of capturing pygmy blue whales and Antarctic blue whales.

“It really blew our mind what we found.”

Constantine says New Zealand makes a great migration path for whales because we’re a long and slim country. She says that until commercial whaling decimated their numbers, blue whales were regularly sited in New Zealand waters.

“It’s exciting to get a handle on how they’re coming back, migrating through our waters.”

She says there have been comprehensive studies on the pygmy blue whales, but Antarctic blue whales – which are the largest whale on Earth – are much more elusive.

“They’re more of an enigma, we virtually never see them. But, in this study, we hear them. We mainly hear them during the Winter months when they’re migrating north – heading from their Antarctic feeding grounds up to breeding grounds unknown in the tropics.”

They suspect the Antarctic blue whales breed somewhere in the waters off Tonga and Samoa.

“Then we hear them again later in Spring as they’re swimming south again back down to feed in the Antarctic.”

Constantine says Antarctic blue whales, which are one of the most critically endangered whales, almost never come near shores and are rarely spotted.

“We rely quite heavily on whale watch companies and oil and gas explorations telling us what they see. So, we rarely ever see them, but here they are in our waters. It’s an exciting thing.”

Antarctic blue whales were hunted so severely it reduced their numbers down to less than 1 percent of their former population.

“Today, after 55 years of protection, our estimate is that they’ve recovered to about 3 percent of their pre-exploitation numbers. The estimate is around 10,000 whales in the whole of the Southern Ocean.”

They found that the whales move up the east coast of New Zealand through Taranaki where there is a lot of oil and gas exploration. While there has already been talk of protecting the pygmy whales in the area, Constantine says there’s now the most critically endangered whale to worry about.

“I think there’s a role for New Zealand to play in ocean protection. There’s nothing more magnificent than watching an Antarctic blue whale, it’s like watching an island swim through the water.”