Reindeer, in fiction and real life, are known for their ability to forge through tough conditions. But extreme weather events tied to Arctic sea ice loss have resulted in the deaths of tens of thousands of reindeer, new research finds.

Reindeer (Rangifer tarandus, also called caribou in Alaska and Canada) aren't the only ones affected. The die off poses risks for nomadic herders, such as the Yamal-Nenets Autonomous Okrug of West Siberia. The oral histories of these people over recent years were incorporated into the new study, which is published in the journal Biology Letters.

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"The private herders who lost all their animals were hardest hit because, for them, it is really a subsistence economy," lead author Bruce Forbes, a research professor at the University of Lapland's Arctic Center, told Seeker. "The private herders have had to become full-time subsistence fishermen to support their families while they rebuild their herds with breeding stock borrowed from their neighbors and relatives."

He and his team conducted the study after noting that two extreme weather events in 2006 and 2013 caused widespread starvation among the Arctic reindeer herds. In 2013 alone, at least 61,000 reindeer died, representing 22 percent of the estimated 275,000 reindeer on the Yamal Peninsula.

Forbes explained that in a typical year, autumn snow falls on vegetation that the reindeer eat. Occasional rains can lead to crusted snow or ice patches that the deer can either push through or eat around.

"Normally stronger bulls would work to break through the ice crust so that females - many of them pregnant - and yearling calves can access the fodder beneath," Forbes said. "The best condition is powder dry snow, which is easy to dig through to the ground layer of lichens and other vegetation beneath."

Rain on snow doesn't cause problems in spring, when it's warmer overall, but it can be catastrophic for reindeer in the fall when it turns into a thick ice crust that can prevent the animals from accessing food.

The scientists combed through climate data from years when mass extinctions occurred, and found they corresponded with thinning of ice in the Barents and Kara Seas. Usually sea ice there increases rapidly in November, but it has been decreasing during some years, likely due to climate change.

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"Open ice or jumbled ice packed together allows more moisture to accumulate in the atmosphere over the sea at a time when the air should be quite dry," Forbes explained. "If the moisture, measured by NASA satellite sensors as specific humidity in the atmosphere, builds up in association with onshore winds, then rain can fall over the adjoining mainland."

The scientists interviewed 60 herders and administrators in the area between March 2014 and April 2016, asking about their observations. The herders, who must manage semi-domesticated reindeer over large tracts of land, recalled extreme weather events that would hurt their herds, but said they're happening more frequently now.

The situation is so bad that mobile slaughterhouses may be deployed in the future, if the sea ice starts to collapse noticeably again. This would d allow the herders to slaughter at-risk animals humanely, Forbes said, rather than letting them starve, which would also be a monetary loss for the herders.