Polar bears aren't the only creatures feeling the effects of climate change up at the top of the world. Scientists tracking the wellbeing of reindeers in the Arctic have uncovered a concerning trend, with warming temperatures in the region actually freezing access to food and leading to a 12 percent decrease in average body mass over just 16 years.

Temperatures across the globe are on the rise, but scientists are particularly concerned with the Arctic where sea ice levels are decreasing by a rate of 13.3 percent a decade. While ice may be on the decline in the sea, it is on the rise on Svalbard, and that is bad news for the hungry reindeer that inhabit this archipelago between Norway and the North Pole.

For the last 20 years, collaborating scientists from Scotland's James Hutton Institute, the Norwegian Institute for Nature Research and the Norwegian University of Life Sciences have monitored the health of the reindeer in the area. Every winter, they capture, measure and mark 10-month-old reindeer calves, and then return the following year to see how they are getting on.

The scientists found that in the 16 years between 1994 and 2010, the average weight of adult reindeers decreased from 55 to 48 kg (121 to 105 lb). The team says that this is because as the winters have grown warmer, they have brought more rain which freezes after falling onto the snow, thus making the ice-sealed food below inaccessible.

This is something of a double-edged sword for the reindeer, because during the two months in which grass is accessible, it is now more nourishing than it was before as a result of 1.5 °C (2.7 °F) increase in summer temperatures. This means female reindeer actually gain more weight before autumn rolls around and conceive more calves, only to then starve in the winter and either abort the calves or give birth to much lighter babies.

Reindeer populations on Svalbard have doubled over the last 20 years, and this may also be a contributing factor by causing more competition for resources in the winter time. The researchers say these forces combined may cause higher amounts of smaller reindeer in the Arctic in the decades to come, but they may be at risk of catastrophic die-offs because of ever-limited access to food.

The researchers are presenting their findings at the British Ecological Society annual meeting in Liverpool today.