Norway's extreme reindeer are eating seaweed to cope with climate change

reindeer eating seaweed
CC BY 4.0 Brage B. Hansen/NTNU

Svalbard's wild reindeer are surviving warmer winters by foraging on, yes, seaweed.

When I think of reindeer – and especially wild Svalbard reindeer, the most northern reindeer population on the globe – I picture them dining on things from the tundra. I imagine them foraging for ferns, mosses, and grasses ... I distinctly do not imagine them eating, of all things, seaweed.

But according to researchers from Norwegian University of Science and Technology's Centre for Biodiversity Dynamics, when the going gets rough, these tough reindeer initiate Plan B: Eat seaweed.

The study begins: "The most rapid climate change occurs in the Arctic, where huge ecological impacts are already evident across terrestrial and aquatic communities. It is now well recognized that gradual loss of sea‐ice, changes in seasonal phenology, and enhanced primary production fueling the ecosystems may alter the abundance and distribution of a multitude of species."

One of the most iconic species of the planet's northernmost climes is the reindeer; and in particular, the Svalbard reindeer, a creature that epitomizes adaptation to the harsh conditions. Living at 79 degrees N latitude, they are built for extremes. Round and robust (and incredibly cute, see photos above and below), they are shorter, smaller, and far more sedentary than their kin on mainland Europe and North America. These traits allow them to survive the extreme frigidity and sparse vegetation of the island archipelago.

With climate change changing the nature of Svalbard's winters, one might think that life would be easier for these stalwart animals – but in fact, warmer weather is making things tougher.

Biologist Brage Bremset Hansen, from the University, and his colleagues have been studying reindeer on Svalbard for decades, and began to notice more and more warmer winters in which rain would fall on the snow and then freeze over, locking in the tundra's treats with a thick layer of ice.

During one especially bad winter (meaning, ironically, warmer) the researchers observed that around a third of the archipelago's 20,000 reindeer were taking to the shore to forage, rather than trying to break the tundra ice to get to the grasses and little plants below.

Hansen said he and his colleagues assumed the reindeer were feeding on seaweed, but, he said, "of course you need more hard-core evidence to show that this was linked to poor conditions, not just coincidence."

So they figured out a way to prove that the creatures were resorting to foraging from the sea, and why. They analyzed scat for isotopes showing the nature of plants being consumed, and combined that with nine years of data for ground ice thickness. According to the University, "they combined this with GPS collar data, and location data from a total of 2199 reindeer observations during those years. They were then able to calculate where the reindeer were with respect to the coastline, and to see if more reindeer went to the coast to feed in years when the ground ice was thicker."

Perhaps it is with little surprise they concluded that indeed, when thick ice prevented access to their preferred food, the reindeer turned to seaweed as a supplementary source of nutrients.

"When conditions are harsh, during bad winters, the reindeer do tend to be more often at the beach, and yes, they eat seaweed, confirming our hypothesis," Hansen said.

Although eating seaweed isn't ideal – it causes diarrhea and doesn't supply all of the nutrients they require – it does prove one thing: The animals are able to adapt, which may bode well for them in an increasingly changing climate.

"The bigger picture is that, although we sometimes observe that populations crash during extremely icy winters, the reindeer are surprisingly adaptive," he said. "They have different solutions for new problems like rapid climate change, they have a variety of strategies, and most are able survive surprisingly hard conditions."

May we all be so lucky...

The research has been published in Ecosphere.

Norway's extreme reindeer are eating seaweed to cope with climate change
Svalbard's wild reindeer are surviving warmer winters by foraging on, yes, seaweed.

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