CRITICAL MASS
Winter often arrives early on Northern range, sometimes with devastating consequences. Even a few inches of snow can cause deer to switch from eating highly nutritious herbaceous plants to consuming woody browse, forcing them on to a negative energy balance. This curtails the physical development and fattening among fawns and can set the stage for excessive fawn mortality during the harsh winter season.
Prospects for survival are especially precarious for fawns, due to their small stature and limited fat reserves. Not only do fawns have shorter legs than adults, which hinders their travel through deep snow, they also lose more body heat from each square meter of surface area than do larger deer. The critical body weight for Northern fawns is between 77 and 88 pounds. Animals weighing less than this lose much more body heat from cold exposure and are more likely to die from malnutrition during long, cold winters.
Therefore, it is essential that Northern fawns are born on schedule and have good nutrition during summer and autumn, so they achieve their full growth potential and accumulate maximum fat reserves as soon as possible.
