Influence of biological and environmental conditions on winter mortality risk of a northern ungulate: evidence for a late-winter survival bottleneck

1. A relationship between winter weather and survival of northern ungulates has long been established, yet the possible roles of biological (e.g., nutritional status) and environmental (e.g., weather) conditions make it important to determine which potential limiting factors are most influential.

2. Our objective was to examine the potential effects of individual (body mass and age) and extrinsic (winter severity and snow melt conditions) factors on the magnitude and timing of mortality for adult (>2.5 years old) female white-tailed deer (Odocoileus virginianus [Zimmerman, 1780] during February–May in the Upper Peninsula of Michigan, USA.

3. One hundred and fifty deer were captured and monitored during 2009–2015 in two areas with varying snowfall. February–May survival ranged from 0.24–0.89 (mean = 0.69) across years. Mortality risk increased 1.9% with each unit increase of cumulative winter severity index, decreased 8.2% with each cumulative snow free day, and decreased 4.3% w...