Just back from my Winter Yellowstone tour and here is one way the bison cope with the stress of winter. By using existing trails and following one another in a line they minimize energy use.
Camera Model Canon EOS 7D
Shooting Mode Aperture-Priority AE
Tv( Shutter Speed ) 1/800
Av( Aperture Value ) 8.0
Metering Mode Evaluative Metering
Exposure Compensation +2/3
ISO Speed 400
Lens EF600mm f/4L IS USM