As the temperatures drop the deer all go into a survival mode and begin to conserve as much energy as possible. They bed as close to the food source as possible, minimize their movements and focus on woody fiber. The bucks also go into this mode and they are trying to rebuild the body mass they lost during the rut. This conservation can trigger them to stop producing testosterone and signals the end of breeding season. Bucks will only producing testosterone while they have hard antlers and therefore they will drop the now unneeded antlers.
The antlers may be hitting the ground but we should not be chasing after them just yet. We know the antlers are likely dropped where the bucks spend most of their time. To invade these areas right now when the deer are all conserving energy can add huge amounts of stress to your local herd. The snow and cold likely will have the squirrels and porcupines bottled up as well so there is no reason to rush in just yet. Wait for the snow to settle and the temperatures to rise. The deer will thank you with bigger antlers next fall!