Because of the changeable weather an ice crust arose on the snow and reindeer could not get food on their own. Reindeer herders fed the main herd with compound feed. The dead reindeer, most likely, have strayed from the main herd.

Climate change is triggering behavior change among animals across the Arctic. In Northern Siberia wild reindeer this summer started migrating almost a month earlier than normal.

Indigenous Nenets reindeer herders say oil and gas operations in the Yamal region - exploration activity that includes hundreds of wells and dozens of trains and tankers - are polluting the environment and harming their animals' health.

In the course of summer, the whole reindeer population of the Nenets tundra will be made immune against the lethal bacteria infection.

Russian officials have said the death of a 12-year-old boy, a member of a reindeer-herding family from the Yamal tundra 1,300 miles north of Moscow, was the first fatality in Siberia linked to the pathogen since 1941. Twenty others have been diagnosed with anthrax.

Animals cannot forage for lichen under the snow crust on the Yamal peninsula.

Sixty-one thousand reindeer starved to death in the northwestern reaches of the Russian tundra in November 2013 in the largest recorded mortality event of its kind.