Our Changing World: Dissecting The World's Rarest Whale

Scoop

22-05-2025

Article – RNZ
It made international headlines last year. What does a scientific dissection of the world's rarest whale involve?
, for Our Changing World
The spade-toothed whale: deep diving, rare, and largely unknown to science – until now.
The elusive species, part of the beaked whale family, grabbed worldwide headlines in 2024: first when it washed ashore 30 minutes south of Dunedin in July, then again five months later when it was dissected.
In December 2024, Our Changing World joined the research team during their week-long scientific dissection efforts to find out what secrets the whale holds.
Rare and elusive
Beaked whales are some of the most elusive marine mammals on the planet because they are so incredibly well adapted to their long-deep-diving lifestyle.
Satellite tagging studies of Cuvier's (or goose-beaked) whales have revealed extraordinary feats of physiology. This includes one dive that lasted a mindboggling 222 minutes – that's longer than the runtime of The Return of the King, the third (and longest) Lord of the Rings movie.
Another dive reached a depth of almost three kilometres. Average dives lasted about one hour – impressive breath-holding for an air-breathing mammal.
As for the spade-toothed whale's diving prowess – well, nobody knows. It's never been seen alive in the wild.
'I can't tell you how extraordinary it is for me personally'
Anton van Helden helped give the whale its common name – spade-toothed – because the single tusk-like tooth erupting from the lower jaw of males looks like a whaling tool called a spade.
Anton, senior science advisor in the marine species team at the Department of Conservation, had described the outer appearance of the whale from photographs taken of a mother and calf that washed up in the Bay of Plenty in 2010. They were originally mis-identified and buried, before DNA analysis confirmed that they were spade-toothed whales, after which their partial skeletons were exhumed.
This meant that when Anton was sent some snaps of the whale that washed up in Otago in July 2024 he knew exactly what he was looking at, and what a rare find it was.
The 2024 specimen is only the seventh ever found (with all but one from New Zealand).
Hence the hum of excitement in the concrete room at AgResearch's Invermay campus in Mosgiel, just south of Dunedin. For the first time ever, scientists got the chance to dissect an intact spade-toothed whale.
New finds: nine stomachs and tiny teeth
The week begins with photographs and whole-body measurements, followed by cutting into and peeling back the thick layer of blubber.
Once the blubber is removed, individual muscles are identified and documented. The massive backstrap muscle across the length of the body is then removed, exposing the organs below. These are photographed, examined and weighed.
Each beaked whale species seems to have a unique stomach plan. This dissection revealed that the spade-toothed whale has nine stomachs. Squid beaks and eye lenses were found inside, along with some parasites that are now at the University of Otago, awaiting identification.
During the week the intact head was removed and brought to the onsite CT scanner.
The tens of thousands of images that come out of the scan, along with the subsequent head dissection, will help the researchers dig into some of the many questions they have around the whale's evolution, how they make and use sound, and how they feed.
For example, tiny vestigial teeth were found in the jawbone of this whale – a throwback to their early evolutionary days when they had more teeth. Now they have evolved to be suction feeders, using sound to echolocate their prey and then employing their piston-like tongue to alter the water pressure and suck them in.
While the focus was scientific dissection, rather than autopsy, the team did find bruising around the neck and head, and a broken jawbone, indicating that the whale had suffered some head trauma that was likely the cause of death.
A collaborative effort, and a reconnection
A large team participated in the whale's recovery and dissection: Te Rūnanga o Ōtākou hapū members and rangatahi, staff from Tūhura Otago Museum, local and international whale scientists, University of Otago staff and scientists, Māori whale experts (tohunga), and staff from the Department of Conservation.
Experts from both knowledge systems – mātauranga Māori and western science – worked alongside each other, with learning going both ways, says Tumai Cassidy from Te Rūnanga o Ōtākou. He was excited to learn from Ngātiwai tohunga Hori Parata and his son Te Kaurinui who answered Te Rūnanga o Ōtākou's call to assist with the dissection.
The whale was named Ōnumia by the rūnanga, after the te reo Māori name for the native reserve stretch of coastline it was found on. The whale's skeleton has been gifted to Tūhura Otago Museum, but it will be a while before it will go on display.
Right now, the bones are in Lyttelton in the care of Judith Streat. Three months in bacteria-filled baths have stripped the bones of flesh, but there is a lot of oil in deep-diving whales, so the process will take several more years.
The kauae, or jawbone, will stay with Te Rūnanga o Ōtākou, says Rachel Wesley.
'Being able to claim the kauae, you know, as mana whenua, under our rakatirataka and in line with old practices from the past has been a huge step forward from what our hapū has been able to do in the past.'
A 3D-printed version of the jawbone will complete the skeleton in the museum.