Our Changing World: Dissecting the world's rarest whale
It's only the seventh time a spade-toothed whale has been documented worldwide, and the first time a complete specimen has been recovered in good condition for examination.
Photo:
RNZ / Tess Brunton
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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.
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.
Cuvier's beaked whales are renowned for their deep and long dives, stretching for more than three hours.
Photo:
Laurent Bouveret / CC BY-SA 4.0 via Wikimedia
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.
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.
DOC rangers assess a washed up whale, thought to be a spade-toothed whale, on the beach at Taieri Mouth.
Photo:
Supplied/Department of Conservation
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).
Spade-toothed Whale
Photo:
Ōnumia CC BY 4.0 DOC
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.
The week begins with photographs and whole-body measurements, followed by cutting into and peeling back the thick layer of blubber.
Scientists are starting the examination in Mosgiel, which is expected to take several days.
Photo:
RNZ / Tess Brunton
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.
The whale head is lifted into the CT scanner.
Photo:
Claire Concannon / RNZ
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 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.
With the blubber removed, the team start investigating the muscles below.
Photo:
Claire Concannon / RNZ
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.
Tumai Cassidy from Te Rūnanga o Ōtākou says the whale was found on their native reserve land on the Taieri.
Photo:
RNZ / Tess Brunton
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.
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