Narwhals and belugas are the only two toothed whales native to the Arctic, and they're often seen in one another's company. You've therefore gotta wonder – could they interbreed? Danish scientists now say the answer is yes, and they've got a hybrid "Narluga" skull to prove it.

The story begins in the 1980s, when a Greenlandic hunter shot an odd-looking whale.

Intrigued by the creature, he kept its skull, which was noticed during a 1990 visit by the Greenland Institute of Natural Resources' Prof. Mads Peter Heide-Jørgensen. He proceeded to send it to the Natural History Museum of Denmark, where it has sat in storage ever since. Based on its morphology, scientists suspected that it may have belonged to a narwhal/beluga hybrid.

In order to find out if that was indeed the case, scientists from the University of Copenhagen recently extracted DNA from the skull, then compared it to DNA from eight narwhals and eight beluga whales. It turned out the deceased whale was in fact the hybrid male offspring of a female narwhal and male beluga.

Its teeth are quite interesting, as they illustrate its dual nature. Narwhals only have two real teeth, one of which spirals out horizontally to form the whale's distinctive unicorn-horn-like tusk. Belugas, on the other hand, have a mouth full of straight conical teeth. The hybrid splits the difference, with long-ish teeth that spiral forward out of its mouth.

Additionally, by performing isotope analysis on the skull, the scientists determined that the whale's diet was different than those of its parents.

"It ate food that would be at the bottom of the sea floor," U Copenhagen evolutionary biologist Eline Lorenzen tells us. "In contrast, both the narwhal and beluga have a diet of fish and squid which are up in the water column, they are not bottom feeders. The carbon signature of the hybrid was equivalent to both walrus and bearded sealed, so although we do not know exactly what it ate, it would have had a similar foraging strategy to those two species."

The researchers have so far not uncovered any other evidence of narwhals and belugas interbreeding within the past 1.25 million years, so they believe that it's either a very rare or new occurrence.

A paper on the study was recently published in the journal Scientific Reports.

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