The average weight of adult reindeer on Svalbard, a chain of islands north of Norway, fell from 55kg (121lb) to 48kg (106lb) in the 1990s as part of sweeping changes to Arctic life while temperatures rose, they said.
“Warmer summers are great for reindeer but winters are getting increasingly tough,” Professor Steve Albon, an ecologist at the James Hutton Institute in Scotland who led the study with Norwegian researchers, said.
Less-chilly winters mean that once-reliable snows fall more often as rain that can freeze into a sheet of ice, making it harder for the herbivores to reach plant food. Some reindeer starve and females often give birth to stunted young.
In summer, however, plants flourish in a food bonanza that ensures healthy females more likely to conceive in autumn. The wild herd studied had expanded to about 1,400 animals from 800 since the 1990s.
“So far we have more but smaller reindeer,” Albon said of the animals on Svalbard, about 1,300km (800 miles) from the north pole. The rising population also means more competition for scarce food in winter.
Arctic temperatures are rising faster than the world average amid a build-up of greenhouse gases in the atmosphere.
Most studies of global warming around Svalbard have focused on polar bears that hunt seals at sea, rather than year-round land residents such as reindeer, Arctic foxes and Svalbard rock ptarmigan birds.
Arctic fox numbers have risen slightly because they thrive in severe ice winters by scavenging dead reindeer, said Eva Fuglei, a researcher at the Norwegian Polar Institute and the Fram Centre who was not involved in the reindeer study.
“All the weak reindeer die – the sick, the elderly and calves,” she said. But that meant foxes struggled to feed the next winter because only the fittest adult reindeer have survived.
This article was first published by The Guardian on 12 Dec 2016.