The reason why 13 whales died off the South Taranaki coast is a mystery that may never be solved, but scientists are learning about how they lived.
Marine ecologist Dr Karen Stockin is collaborating with other scientists in studies that may indicate how many of the whales there are, where they roamed and if they ate plastic.
With growing concerns about global warming and plastification of the world’s oceans, this was important research, she said.
What caused these sperm whales’ deaths was not known, although it was likely they were still alive when they stranded, not washed up dead.
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The first eight sperm whales were found along a stretch of coast at Kaupokonui on the morning of May 24 after a very stormy night.
The number escalated to 12 as others washed up in the next few days.
A 13th whale that washed up on a beach near Hāwera last weekend was thought to be from the same pod.
Veterinary pathologists arrived from Massey University in Palmerston North to examine the whales the day after the first ones were found.
A necropsy was not done because due to the state of the animals, it would have been unlikely to show why they died, Stockin, who is the director of the Coastal Marine Research Group at Massey University in Auckland, said.
However, skin and blubber samples were taken from the whales with the permission of iwi and the Department of Conservation.
All the whales appeared to be from a bachelor pod – a group of males travelling together.
Twelve of the dead whales had been identified as male, with Stockin suspecting the one thought to be female would turn out to be another male on DNA examination.
“I’m sceptical that that one is actually female, it’s pretty unlikely a lone female would have been in a bachelor pod.”
By studying the DNA in the whales’ skin samples, Stockin and colleagues at Massey will determine if they are related, or not.
It’s not clear how many sperm whales live around New Zealand, she said.
“We would not necessarily expect them to be related. As bachelors they have orginated from different clans but if they do prove to be related in some manner, that could be insightful about the NZ population size,” she said
Isotopic signatures contained in the blubber samples are being studied by Stockin and colleagues at NIWA to determine the whales’ foraging behaviour and what they ate.
“We know that squid is a part of the diet, but how this relates to the broader tropic positioning of sperm versus pilot whales remains unclear for both species in NZ”
Stockin has also made a request to the hapu involved for a tooth from each whale they are studying, so she can learn about the historical diets.
“If the iwi agree to us having a tooth from each animal we can age each whale and also see how their diet may have changed throughout the whale’s lifetime.”
Another part of the study was looking for toxins within the tissues recovered from each whale
“They have a nasty habit of ingesting things they shouldn’t, including plastics,” she said.
Stockin who is currently collaborating with NASA climate scientists on the satellite tracking of pilot whales during stranding events, said she has requested sate data and imagery over the Taranaki region days prior to the recent stranding.
She hopes they can find out where these whales were before the stranding.
“If we access the satellite imagery for the times around the stranding, we may if visibility permits, gain a better idea of their movements and total number prior to the stranding.” she said.