Sorry for this generic answer but it is the truth.
When the snow gets deep enough to cover their feed up high to where they can''t get to it. It might start in October or December, it just depends on the year. I know of a herd in Utah that winters at 9500' + just because the wind blows the snow off of the high ridge that they live on and there is feed all winter long.
Like this last winter for example. Where I live here the winter was so mild I never saw any elk come down as usual. In general there are several hundred not far from the house by December/January but they never made it all this year.
I have done everything possible to get my kids involved in hunting. Every time out whether it be scouting, camping or during the actual hunt, I will challenge them to find their way back without using any electronics (GPS). Also without a compass. They know by now that I am going to challenge one of them, so right off the bat when leaving our vehicle or camp they will start picking out land marks to help them out. Makes me and them feel confident that if we were to somehow separate that they...