Wairarapa coast at Tora. PHOTO/GRACE PRIOR
The biggest animal to ever roam the earth has been discovered using Wairarapa as part of its migration route.
A study led by a University of Auckland scientist found New Zealand waters provided an important migratory route for the Antarctic Blue Whale, which had a heart the size of a small car and outsized any dinosaur – even megalodons.
Hydrophones, or underwater microphones, anchored at the bottom of the ocean around central New Zealand recorded the whales’ low-frequency calls loud enough to be heard across hundreds of kilometres to monitor their locations, an Auckland University release stated.
The study had shown the giant creatures travelled a route that ran through the South Taranaki Bight, an area off the west coast of the North Island and above the South Island.
“Antarctic blue whale detections were greatest in the South Taranaki Bight during winter, when the whales were northbound, heading for warmer waters to breed, before peaking again in spring, when the whales were returning to the Antarctic to feed, the research found.
“Antarctic blue whales were also detected to a lesser extent off the east coast of central New Zealand, offshore from Kaikoura and Wairarapa.”
The study, published in the Frontiers of Marine Science journal, was a joint effort by the University of Auckland and the National Institute of Water and Atmospheric Research, with collaborators from Texas A&M University in the United States and acoustic monitoring firm JASCO Applied Sciences in Australia.
Institute of Marine Science’s Victoria Warren, who led the research, said: “The research shows that New Zealand waters provide an important habitat for these incredible creatures”.
“These animals are critically endangered, and we need to do everything we can to protect them.”
Antarctic blue whales could reach up to 30 metres in length and 200 tonnes in weight, but were hunted to the brink of extinction last century.
The United Nations estimated a population of 3000 in 2018 – compared with a peak of as many as 200,000 whales before commercial whaling, the report said.
The acoustic data pointed to the possibility that Antarctic blue whales may breed in New Zealand waters since their calls were heard during the breeding season of September and October, but the evidence wasn’t conclusive.
New Zealanders may spot an Antarctic blue whale on rare occasion. However, the creatures were notoriously difficult to distinguish – visually, at least – from the somewhat smaller, but still giant, pygmy blue whales, Auckland University said.
To get a clearer picture of both types of blue whale habits, scientists eavesdropped using microphones deployed at depths ranging from 100 to 1500 metres. While identifying the sub-species visually could be difficult, it was straightforward by sound.
The data showed pygmy blue whales seemed to congregate in the South Taranaki Bight, especially from March to May, which supported other research findings and highlighted this area was significant for both types of blue whale.
Underwater microphones were deployed in 2016 at four locations around central New Zealand – the South Taranaki Bight, Cook Strait, and off the coasts of Kaikoura and Wairarapa, and in 2017 at three of those locations.
Over 106.5 days, 20,751 blue whale calls were detected, with both sub-species turning up at all of the locations.
“This research illustrated the value of long-term deployments of underwater microphones, for monitoring rare and hard-to-observe animals such as large migratory whales,” associate professor Rochelle Constantine, one of the co-authors of the paper, said.
Potential threats to whales ranged from collisions with ships to plastic pollution and anthropogenic [human created] noise from sources such as oil and gas exploration, which disrupts their communication.
Warming and changes in acidification levels of the ocean due to climate change had the potential to alter marine ecosystems faster than whales could adapt, the Auckland University statement said.
- Additional reporting by Grace Prior.