A narwhal is still swimming with a pod of belugas in the St. Lawrence. Is this the year a narluga will be conceived?

During a routine observation of the St. Lawrence River beluga whales in 2016, marine biologist Robert Michaud noticed the pod had acquired a peculiar straggler.

Swimming with the belugas was a male narwhal: a spiral-tusked, 2,000-pound mammal whose kind is seldom seen wandering this far south of the Arctic Ocean. To Mr. Michaud, the president and scientific director at the Group for Research and Education on Marine Mammals, the visitor clearly stood out from the pack for his obvious tusk, mottled grey complexion and deeper vocalizations.

Despite those differences, Mr. Michaud is seeing signs that the newcomer, approximately 12 years old, is showing interest in mating with a beluga. Such an event would produce an ultra-rare cross-breed that occurred only once before in recorded history: a narluga.

“There are too many question marks to say that a narluga will happen for sure, but if it does, it would be one of the coolest things I’ve seen in my 30 years doing this,” he said in an interview.

Cross-breeding in waters happens semi-frequently between species of close descent. A 2016 study of hybridization of marine animals, for example, recorded the existence of nearly 20 whale and dolphin hybrids. Belugas and narwhals, two siblings of the Monodontidae family who are roughly the same size and live mainly in arctic waters, appear well-suited to reproduce.

But Mr. Michaud said narlugas are rare because the genomes of both parent species indicate that their last common ancestor lived approximately five million years ago. That’s enough time for each to develop distinct vocal ranges and morphology, which could make the acts of communication and sex difficult – perhaps even impossible.

Yet, he wonders if the greatest hurdle to reproduction for the lone narwhal will be social acceptance. Human societies have sociological taboos – such as marrying family members – and Michaud says these animals should be thought of as living with similar kinds of social rules.

“The question becomes: is the narwhal integrating well enough socially to reproduce? Who knows if in societies of belugas there is a sentiment of ‘A narwhal? Nope. We shouldn’t do that.’”

Marine observation is a challenging discipline. Even with the help of underwater drones, Mr. Michaud’s team relies on just minutes of yearly footage to make behaviour-based observations about the sea mammals. In last year’s videos, Michaud noticed that the narwhal was copying the belugas and performing pelvic thrusts on other males, a telltale sign that a male beluga is ready to reproduce with a female.

“If our analysis of what these movements mean are correct, we should at least be on the lookout for offspring in these next few years.”

If a narluga were to be born in the St. Lawrence waters, it would join scant company. The first and only documented case of a narluga dates back to 1990: An Inuk sustenance hunter had killed three whales off the shore of West Greenland, and their strange skulls with jagged teeth caught the attention of Mads-Peter Heide Jorgensen, a Copenhagen-based marine researcher.

Dr. Heide-Jorgensen brought one of the unusual skulls into his lab for testing. By 2019, with the advent of more sophisticated DNA sequencing technology, he confirmed that the skull he had borrowed from the hunter had in fact once belonged to the offspring of a female narwhal and male beluga.

He and his team deduced that the narluga had been much bigger than both his parents, and had approximately 18 teeth – more than a narwhal’s two, but fewer than a beluga’s usual 30 to 40 – that twisted left like little tusks. The marine researcher said that, while there was no way of knowing for sure, he doubted the hybrid had been fertile.

“That skull was definitely the weirdest thing I’d ever seen … still now,” Dr. Heide-Jorgensen said. He came across another strange-looking whale in 2001, when a similar creature with tusks for teeth was hunted and brought ashore – this one on the coast of West Greenland, too. He said the animal looked like a narluga, but he never collected DNA samples to confirm its ancestry.

Belugas and narwhals live in close proximity around the West Greenland shoreline, which could make them more likely to reproduce. The similar bunching of marine animals is a scenario we will probably see in Canada’s Arctic waters over the next decades because of greenhouse gas emissions, according to a 2020 study from Dalhousie University climate impact researcher Andrea Bryndum-Buchholz.

The research predicts that, by 2099, the number of marine animals will decrease by a quarter in the Atlantic and Pacific waters surrounding Canada, while increasing in the Arctic by roughly as much, if the change in GHG emissions remains stable. Various species living in closer quarters from each other could potentially increase the chance for hybrid reproduction, but only if biology permits, according to Dr. Bryndum-Buchholz.

“We can expect to see animals displaced and move north more and more, living closer to one another,” she said in an interview. “But narwhals and belugas already live far up – eventually, they can’t move north anymore.”

Dr. Bryndum-Buchholz said it was perhaps the hunt for food that instead led the St. Lawrence narwhal downstream.

“Either that,” she said, “or he was just really lost.”

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