How reindeer on an Arctic island survived thousands of years through inbreeding

Among their many adaptations to life on the Svalbard, reindeer have developed the ability to digest moss instead of lichen. (Bart Peeters)

Researchers are trying to understand how a subspecies of reindeer living off an Arctic archipelago have managed to quickly adapt to an environment they've only been in for less than 10,000 years and survive near-extinction.

In a new study published Tuesday by the Norwegian University of Science and Technology (NTNU), researchers analyzed the DNA of Svalbard reindeer, a subspecies that migrated from Russia to the Norwegian islands roughly 7,000 to 8,000 years ago.

Throughout their time in Svalbard these reindeer have managed to evolve quickly, adapting to digest plants native to the islands, have shorter legs in comparison to other subspecies and change their behavioral patterns to fit the environment's extreme cold. In the early 1900s the species was nearly extinct due to over-hunting, but today the population is at a stable 20,000, according to the study.

By evolution's standards however, researchers say, these reindeer were destined to fail, since many species that are secluded to a single area with few others are likely to inbreed which can lead to diseases, genetic mutations and poor biological fitness, also known as inbreeding depression.

Despite this, the Svalbard reindeer have managed to avoid harmful mutations through a phenomenon called genetic purging, where the healthy animals born out of inbreeding are the most likely to reproduce since the reindeer with health complications are likely to die before they get the chance to reproduce, or if they reproduce, they usually have less offspring, according to the study.

Similar studies have also explored genetic purging in an effort to save vulnerable species, like the cuvier's gazelle and dama gazelle. A 2021 study published in Heredity looked at the benefits of inbreeding to help the animal's low population that have been impacted by habitat destruction, desertification and over-hunting in their native region of North Africa.

Researchers acknowledged the unlikely survival of the reindeer in a news release, saying they're now looking into how long ago harmful mutations were ruled out among the subspecies.

"Paradoxically, in the long run, inbreeding can be beneficial," postdoctoral researcher Nicholas Dussex said.

"We will continue to work on this, using DNA samples collected from bone remains and antlers of animals that lived several thousand years ago. This way, we can see whether these mutations have disappeared quickly over a few centuries or if it has happened gradually over several thousand years,” Dusses continued.

REINDEER DNA MAY NOT BE ABLE TO KEEP UP WITH CLIMATE CHANGE

Despite the reindeer's quick-adapting genetics, study authors are concerned there may be one thing their DNA may not be able to overcome; climate change.

While every corner of the world is feeling the effects of global warming, the Arctic region, particularly Svalbard, is experiencing warming at a much faster rate; with temperatures in the Norwegian archipelago rising six times faster than the rest of the world.

During the summer months, Svalbard can experience temperatures between 5 C and 8 C, however, in July of 2020 the island recorded its hottest day on record at 21.7 C.

With melting sea ice, permafrost and rising water levels the researchers say they're concerned if the Svalbard reindeer have evolved enough to adapt to a dramatically changing environment.

"Even though our results show that the Svalbard reindeer managed to adapt relatively quickly to a completely new environment after they colonized the islands, they might have trouble adapting to today's rapid warming. They may have simply lost too much genetic variation," professor of Conservation Biology at NTNU Brage Bremset Hansen said in a news release.

With files from Michael Lee.