From Wildlife.org:
Lower snow levels in Minnesota winters means fewer vulnerable deer for packs to prey on
The first sign that Thomas Gable and his colleagues were approaching a kill site was the calls of crows and eagles cutting through the winter silence in northern Minnesota.
The ecologist in the Voyageurs Wolf Project at the University of Minnesota was surveying wolf predation last winter when snowfall was particularly low. He and his colleagues had GPS collars on wolves in two packs near Voyageurs National Park. When data were relayed back to Gable and his team’s computer, they looked for the telltale cluster of location points that indicated a potential kill.