An Index of Winter Weather Severity for Northern Deer

Abstract

The relative severity of winter climate for white-tailed deer (Odocoileus virginianus) can be determined by using rather simple and inexpensive equipment to measure the principal stressors, air chill and snow hazard. A rating for air chill is derived with a specially designed chillometer described in this report. Depth of the snow pack and its supporting quality, obtained with a compaction gauge, yield the snow''s hazard rating. Respective air chill and snow hazard ratings are summed to compute a weekly severity index. The cumulative total of these values constitutes the seasonal score. Trials with this system in Michigan''s Upper Peninsula indicate that it provides a reliable means for judging the physical welfare of yarded deer; hence, their probable mortality rate can be predicted through inspection of collected data as winter progresses. Moderate to heavy deer losses occurred during winters in which the season''s severity index exceeded a value of 100 among the various stations across the peninsula.