Beluga whale

Image by cibertrip/iStock

Remember Romeo and Juliet? Star-crossed lovers and all that? Now, picture this: Instead of angsty teenagers, they’re whales; a narwhal (the unicorn of the sea) and a beluga (the protagonist of a children’s song). That’s basically the story behind a strange skull that’d been sitting in the Natural History Museum of Denmark for 30 or so years. But scientists were only recently able to unravel it.

The trio of weird-looking whales

In 1990, narwhal scientist Mads Peter Heide-Jørgensen found the aforementioned odd skull at an Inuit hunter’s house in Disko Bay, in Greenland. The skull came from a really weird whale, said the hunter, Jens Larsen. He’d killed it, and two others with it, in the 1980s while hunting for food. All three had the rounded flippers of a beluga but the smooth tail of a narwhal. Their skin was solid gray, unlike a beluga’s brilliant white or a narwhal’s mottled shades.

But perhaps the strangest thing about these whales was their teeth: There were only a few on top and bottom, jutting awkwardly out of the mouth. Compared to a narwhal’s single long tooth and a beluga’s neat rows, this creature was bizarre.

Heide-Jørgensen mused that perhaps this skull came from a beluga-narwhal hybrid (otherwise, perhaps it was a rather unusual beluga whale). But at the time he didn’t really have a way to verify his hypothesis, so the skull remained a mystery.

Time passed, science advanced, and the skull came back out in the open

Fast-forward nearly 30 years, and the skull finds itself being pulled off its shelf by Eline Lorenzen, the collection curator for the Natural History Museum of Denmark. Lorenzen and her team carefully retrieved the creature’s DNA from its teeth and bones (since the skull was first collected, scientists had gotten much better at analyzing small amounts of DNA from old bones). Now, they could unravel the bizarre whale’s secrets.

And they found the skull did belong to a hybrid: His mother was a narwhal and his father was a beluga, making him a first-generation hybrid — a narluga.

“It’s like if you took 50-percent beluga and 50-percent narwhal and shoved their teeth in a blender, that’s what would come out,” Lorenzen told The New York Times.

Curious about this unusual whale, Lorenzen and her team analyzed the carbon and nitrogen in its skull to get a better understanding of what it ate. They found its diet was closer to that of a walrus (eating things off the seafloor) than either a beluga or narwhal. Its odd teeth may have forced it to figure out a different way of eating, but it must have worked, since the narluga survived into its adult years.

It’s unclear why the narwhal and beluga mated. What scientists do know is that they are the only toothed whales in the Arctic and their breeding seasons overlap. As far as species go, they are closely related, but they began evolving separately some 5 million years ago. Additionally, their genomes show no interbreeding for the last million years at least, suggesting that hybridization is rare.

But occasionally, the two species will mix and mingle. In Canada’s Saint Lawrence River, a young male narwhal lives with a pod of male belugas. They play together, just like any two belugas would. It’s unclear how the narwhal found his unlikely family. However, when young whales are separated from members of their own species, they tend to wander to strange waters, attempting to befriend humans, boats, and other types of whales. Perhaps that’s how this odd couple came together?

Beluga whale narwhal hybrid animal skullBeluga whale narwhal hybrid animal skull
Image by A. Thorburn/Wikimedia Commons

Hybridization between species isn’t unheard of

People have long believed hybridization is a very rare occurrence between different species. However, it seems to be more common than originally thought. Many humans, for instance, have genes from our dead cousins the Neanderthals and Denisovans.

And there are twisting tales of hybrids that make you wonder — what on Earth led them to mate? Like, take pizzly bears, for instance. Scientists thought the polar bear-grizzly hybrids were becoming more common due to climate change, but once they dug into their DNA, they found a much stranger story: a small, incestuous family. But how exactly that came about remains a mystery.

The same mystery shrouds the narluga. Considering whales usually only have one baby at a time, one can’t help but wonder how there were (potentially) three narlugas together. And, can the narlugas have offspring themselves? Many hybrids are infertile, after all.

Hybridization has actually played a substantial role in several species’ evolutionary histories: The various bear species have adopted parts of one another’s genomes into their own. Jaguars got some of their optic nerve genes from lions. In fact, once upon a time, all five big cats of genus Panthera were interbreeding.

But while hybridization has influenced many species’ pasts, some scientists now worry about how it’ll affect their future. It could reduce biodiversity, making certain genes die out and thus making species less resilient to change. Some people believe this problem will be especially potent in the Arctic, due to climate change.

Perhaps “Baby Narluga (in the deep blue sea)” will soon dethrone “Baby Shark” as the next big children’s song.