Svalbard reindeer thrive as they shift diet towards ‘popsicle-like’ grasses

As the Arctic warms, concern for the plight of Santa’s favorite sleigh pullers is mounting. But in one small corner of the far flung north – Svalbard – Rudolph and his friends are thriving.

Warmer temperatures are boosting plant growth and giving Svalbard reindeer more time to build up fat reserves; they also appear to be shifting their diets towards “popsicle-like” grasses that poke up through the ice and snow, data suggests.

Smaller and plumper than their Lapplandish cousins, yet boasting impressive antlers nonetheless, Svalbard reindeer inhabit almost all non-glaciated areas of the Svalbard archipelago, which sits just 500 miles (800km) from the North Pole.

Like other Arctic regions, Svalbard has experienced thicker snowfall, and more frequent rain-on-snow events – where rain falls on an existing snowpack and freezes – in recent years, making it harder for reindeer to dig for food.

Reports of mass reindeer starvations in Russia, and declining caribou populations in Canada and Alaska, have also prompted concern for Svalbard’s reindeer. Yet, in the most productive parts of the archipelago, reindeer populations have flourished in recent decades.

To investigate what might be driving the population increase, Tamara Hiltunen, a doctoral student at the University of Oulu in Finland, and her colleagues turned to annual blood samples collected in late winter as part of a long-term monitoring study. By comparing the proportion of carbon and nitrogen isotopes in these samples, they could infer what kinds of plants the reindeer had been eating in preceding weeks.

The research, published in Global Change Biology, suggested that between 1995 and 2012 – a period marked by the normalization of rain-on-snow events, increased summer temperatures and a growing reindeer population – there was a dietary shift away from low-growing mosses and towards grass-like “graminoid” plants.