Ligers, and tigons, and grolar bears, oh my! Hybrid animals have long been a source of public and scientific fascination. These sort of combination species aren't limited to land animals, though.
Beluga whales and narwhals have known to mate to produce narlugas.
In addition to being fun to say, narlugas are pretty interesting animals. According to Vox, the skull of an unfamiliar whale was discovered in Greenland in the '80s that bore similarities to the beluga and narwhal — but wasn't distinctly either. It appears that narluga mashup wasn't even a one-time occurrence, though.
Vox said hunters have reportedly spotted this hybrid whale swimming in the Arctic.
The narluga stands out from a beluga or a narwhal for a couple of reasons. Smithsonian magazine reported that it has a large head, "its snout and lower jaw were particularly burly, and its teeth shared some similarities with both narwhals and belugas." It doesn't, however, have the narwhal's tusk, according to a LiveScience report on a Nature study.
It's this tusk feature that highlights a potential issue with cross-species breeding like this. Although, initially babies born to narwhal and beluga parents may be stronger than those that are the result of in-species breeding, hybrid animals don't have evolutionary survival traits.
"This change is happening so rapidly that it doesn't bode well for adaptive responses," ecologist Brendan Kelly, who authored the Nature study, said. The narwhal tusk "contributes to breeding success," per LiveScience.
It can also be used for hunting, which is something narlugas wouldn't be able to do.
And, LiveScience notes that scientists are concerned that Arctic hybrid animals are occurring because of environmental factors — further evidence that something is wrong in our natural world.
For example, LiveScience reported that melting polar ice could be to blame for hybrid species of Arctic animals, with barriers between species disappearing and warming temperatures allowing animals to co-exist that may not previously have been able to.
Of course, it is possible that narwhals and belugas always have or would have mated. The skull from the '80s shows that this has been happening for decades and both species are from the same whale family and occupy the same Arctic waters.
Still, could sustained interbreeding lead to the decline of the parent species? Conceivably, yes.
Ultimately, LiveScience reported that the study from Nature on narlugas and other hybrid species seeks to "[push] policy-makers to incorporate hybrids into their management and protection plans."
As LiveScience noted, the Endangered Species Act doesn't currently protect hybrids. Raising awareness that this is happening, and looking into why, is important to ensure the survival of all hybrid species and their parent species.