Before the development of the Treasure Valley, deer would migrate into the valley from the higher elevations during the winter months to rest and save vital energy (this is how Deer Flat got its name). Now, with development blocking access to the valley, they must try to winter in the Boise Foothills, generally a much tougher place to live. They are most abundant in the area around Lucky Peak (the mountain) above Barber Flats. Which comprises the Boise Front Segment of the Boise River Wildlife Management Area.
Deer have limited fat supply and have a tough time adding to it during these critical months. Every time they must move because people or pets disturb them, they take a step closer to death. If they make it to Spring prior to their energy being used up, they survive. If not, they die. It's as simple as that.
We all must be respectful of this natural process and stay away from these areas during the January to April time period. Even in areas that may not be closed it is still important to keep your pets under control.