Narwhal tusk Arctic

Scientists use genetics to study how the world’s three narwhal populations are affected by climate shifts

Researchers used DNA testing and habitat modelling to examine past narwhal populations and predict what a warming future will mean for the mysterious sea creature of the Arctic

If you want to learn about your ancestry, you can spit into a test-tube and retrieve your DNA results a month later online. 

Scientists seeking to learn about the genetics of the narwhal had to use more elaborate methods to gather DNA samples of the deep-diving whale that lives in the ice-cold waters of the Arctic. 

Hoping to unravel the demographic history of the narwhal, often called the unicorn of the sea, the scientists collected narwhal tissue samples from Inuit hunters in Canada’s far north and Greenland, and tested narwhal remains from archeological digs in northern Europe and Russia. 

They even got permission to take samples of narwhal tusks from the King of Denmark’s throne chair, made from Norwegian narwhal tusks and guarded by three life-sized silver lions with manes of real gold. 

“They had special access to be able to drill little tiny bits of tusk from that throne,” said Steven Ferguson, an Arctic marine mammal research scientist with Fisheries and Oceans Canada.

Ferguson is one of 15 co-authors of a study, published on April 21 by the Proceedings of the Royal Society B: Biological Sciences, that helps unwind a little bit more of the mystery and mystique surrounding the narwhal, a close relative of the beluga whale. 

Until recently, little was known about the light-coloured cetacean most commonly recognized for its spiralled tusk — a tooth extending through its upper lip. Only in 2017 did scientists discover the narwhal uses its tusk, a sensory device, to smack fish before swallowing them. 

Using a combination of genetics and habitat modelling, Ferguson and other scientists investigated how past climatic shifts affected the distribution of the narwhal, one of the Arctic species most vulnerable to climate change. 

They discovered low levels of genetic diversity among the world’s three narwhal populations, the two largest of which are found in Canada.

The scientists also found that habitat availability has been critical to the success of narwhals over the past tens of thousands of years, raising concerns about the fate of the migratory whale in a rapidly warming Arctic

There are approximately 200,000 narwhals in the world. 

Populations are named for where they summer. The vast majority of narwhals are found in Canada, in two groups known as the Baffin Bay and Hudson’s Bay populations. A third population, numbering about 10,000 animals, is found in Greenland, extending to Svalbard — an island between Norway and the North Pole — and as far as Russia. 

“It’s pretty remarkable that Canada has this resource but it’s also a lot of responsibility,” said Ferguson, who worked with Inuit hunters to gather tissue samples for the study. 

“We are the ones who are going to have to manage and conserve this species going forward into the future.” 

Steve Ferguson NRCan

DFO scientist Steve Ferguson in the field, conducting research on the world’s narwhal populations. Photo: Steve Ferguson

Narwhals appear only to have ever been an Atlantic species, and all three populations are closely related. Researchers found narwhals have one of the lowest genetic diversities of all marine mammals.

“I still don’t think we’ve quite solved that puzzle as to why it is so low,” Ferguson said in an interview. “Maybe there was some kind of bottleneck way back in the past. This history that’s been explained by the genomic study here hasn’t really found a good explanation for that.”

The study found a long-term, low overall population size that increased when suitable habitat expanded following the last Ice Age. Like other polar marine predators, narwhal populations contracted into smaller areas during the last glaciation. 

“It’s a bit of a mystery as to how fragmented they might have been,” Ferguson said. 

The study also looked into the future, forecasting what impact global warming might have on populations.

Researchers estimated a 25 per cent decline in habitat suitability by 2100, with a 1.6 degrees northward shift in habitat availability, suggesting narwhal habitat is likely to contract as sea temperatures rise and sea ice continues to melt.

The genetic ghost hunters

Ferguson said there will be a slight decrease in populations, including in the east Greenland group. 

Narwhal distribution will be further affected in the near future by increased human encroachment, changes in prey availability, new competitors and increased predation by killer whales, according to the study. 

“More open water is good for narwhals to some extent,” Ferguson said. “But they will have competitors and disease and problems coming from the south [and] that’s going to continue to push them further north.”

Much depends on narwhals having access to the habitat they need to thrive, he said. 

“Baffin Bay seems to be a perfect spot for them right now, at least in winter. They’re really deep diving animals, well adapted to diving to extreme depths, up to 2 kilometres. Baffin Bay allows them to do that and has some really good food.”  

All other Arctic marine mammals are circumpolar, meaning they are found around the world. 

“But narwhal are unique,” Ferguson said. “They really seem to have this Atlantic Ocean habitat. So there’s an open question as to what might happen as we continue to lose sea ice.” 

The Arctic is warming at an unprecedented rate. A new study, published in Geophysical Research Letters, predicts summer Arctic sea ice will disappear before 2050, with devastating consequences for the Arctic ecosystem.

Narwhals most vulnerable to increased shipping in Arctic

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