Natural History

a: beluga skull b. “narluga hybrid” c. male narwhal skull.

In the 1980s, an Inuit subsistence hunter in Greenland killed three gray whales that looked suspiciously like belugas at first. However, they were oddly gray. The fins resembled a beluga’s, while the tail looked like that of a narwhal.

The hunter kept one of the skulls, eventually donating it to science, where became the property of the Greenland Fisheries Research Institute. A scientist working for that institute, Mads Peter Heide-Jørgensen,hypothesized that this skull came from a hybrid between a narwhal and a beluga.

It was only today that a study was released in the journal Nature that revealed that this whale was indeed a hybrid. The DNA analysis revealed that male beluga mated with a female narwhal to produce the creature.

The skull was quite strange. Belugas have 40 homodont teeth. Narwhals are toothless, except males. The males have one really long canine tooth that sticks out as a tusk. Sometimes, they have two, but most have only one true tooth. It is spiraled like what is expected form the mythical unicorn. They do have only a few vestigial teeth.

The hybrid had 18 teeth, many of which were pointed out horizontally and spiraled like the vestigial teeth of the narwhal.

Isotopic analysis also revealed that the hybrid had a different diet from either parent species, both of which catch fish or squid in the open water. The beluga hunts fish at depths of up to 500 meters, while the narwhal hunts fish or squid at depths exceeding 800 meters. The isotopic analysis revealed that the narluga was eating mostly benthic prey, which means it was eating mostly shellfish from the sea floor.

So this study raises so many questions. Analysis of the narwhal genome revealed that gene flow between the two species stopped between 1.25 and 1.65 million years ago. The initial split happened around 4 million years ago, and that study thought that an viable hybrids would be unable to reproduce. However, the authors of the study cautioned that a larger sample size of individual narwhal and beluga genomes from across their range might reveal more recent dates on when gene flow stopped (if it did at all).

So it is not entirely clear that this hybrid would have been sterile, but we also have no further evidence of hybrids anywhere else.  It is quite possible that these hybrids could be fertile, and if they are, climate change could cause the eventual genetic extinction of the narwhal.

The morphology and feeding behavior this odd whale might point to the origins of the narwhal. Perhaps the ancestral narwhal was a benthic feeding whale that later lost its teeth to become a whale that hunts squid and fish at great depths with an almost toothless mouth.

Having teeth like the hybrid is a great adaptation for this particular diet, because the forward pointing teeth can poke around and dislodge shellfish more easily.

If these hybrids are fertile, then one could see the eventual development of a hybrid whale species that has its own niche as a benthic feeder in the arctic.

It is an amazing find, and chances are there will be more discovered. Further, as scientists examine genomes from belugas and narwhals from a wide geographic distribution, we might see evidence of some hybridization.

Hybridization could also increase genetic diversity in narwhals, but if these hybrids must eat a fundamentally different diet than narwhals do, it might become difficult for these hybrids to add their genes to narwhal populations. They just cannot hang out for extensive periods of time, before they have to split off and engage in divergent feeding behavior.

So this discovery does generate lots of speculation and raises several important questions that need to be addressed.

Pretty cool.