Other than making it easier to track and see how many deer are in an area, and making it easier to spot deer, light snow won't cause a great change in deer behavior. When it gets deep enough to start covering their food sources, then you will see changes in their activity and where they congregate. For one thing, they will be more active as they search out food. And if there is a good food source that is still available, more deer will congregate in the area. They will also feed longer to get their bellies full. That makes them more susceptible to hunting.