Climate change forces reindeer to resort to eating seaweed

In the face of climate change, reindeer are resorting to eating kelp seaweed, according to new research. The creatures in question are Svalbard reindeer (Rangifer tarandus platyrhynchus), a sub-species of wild reindeer. As their name suggests, they're native to Svalbard, an archipelago about halfway between Norway and the North Pole. Historically, seaweed was not part of the diets of these reindeer.

The researchers' suspicions were first aroused when they saw reindeer feeding at the shore. Reindeer in the region have since been pictured eating seaweed, but the research hangs on more substantial evidence: reindeer poo, gathered from habitats both near the shore and farther inland. Isotopes of carbon, nitrogen and sulphur found in the waste confirm that seaweed has become a fixture of the reindeers' diet.

The researchers think that the change could be caused by rain associated with increasingly-frequent warmer winters. By Svalbard's standards, "warmer" is relative, of course – average winter temperatures in some parts can be as low as -20 degrees C (-4 degrees F).

The rain freezes as a layer of ice on top of the packed snow, blocking access to the reindeer's ordinary diet of moss, lichens, grass and small plants. This ground is is the same phenomenon causing the weight loss in reindeer recorded in separate research reported by New Atlas in 2016.

Svalbard reindeer are well-adapted to extremely cold conditions (Photo: Erik Ropstad)

These "ice-locked pastures," as they're called in the research, are known to cause population fluctuation in wild reindeer and caribou populations more generally. The formation of this temporary ground ice, or basal ice, should not be confused with the permanent and significant decrease of Arctic sea ice which is caused by climate change.

By combining this data GPS collar readings, recorded visual sightings and annual date on ground ice thickness, the researchers have determined that, when ground ice is thicker, reindeer make for the coast. Conversely, they don't eat kelp when they don't have to.

The reindeer don't totally switch diet, though. "It seems they can't sustain themselves on seaweed," biologist Brage Hansen explains in a press release. "They do move back and forth between the shore and the few ice-free vegetation patches every day, so it is obvious that they have to combine it with normal food, whatever they can find."

Despite this, the seaweed is taking a toll on the reindeer: diarrhea, which is thought to be caused by the salt content. If there's a silver lining, it may be the reindeer's adaptability in the face of adversity. Not all species are as fortunate.

"Although we sometimes observe that populations crash during extremely icy winters, the reindeer are surprisingly adaptive," Hansen adds. "They have different solutions for new problems like rapid climate change, they have a variety of strategies, and most are able to survive surprisingly hard conditions."

That said, the researchers are yet to examine the effect of the change in diet on the reindeer's nutritional intake.

There are some 20,000 Svalbard reindeer – the most northerly reindeer population in the world. Their portlier frame is better suited to extreme cold. They are well adapted to eating large quantities of moss, to make up for its low nutritional value.

The research was carried out by a team from the University of Alaska, the University of Aarhus in Denmark and The University Centre in Svalbard. Their research is published in the journal Ecosphere and available to read online.

The Arctic is the scene of the most rapid climate change on Earth, but the adaptability of life in the region is poorly understood. More research of this kind is needed to begin to understand the impact of climate change on biodiversity in the Arctic – and beyond.

Sources: Ecosphere, Norwegian University of Science and Technology and SINTEF