This will be our first winter with our outdoor rabbits. Everything I've read said rabbits can endure the cold better than the heat. My questions are, how cold can they handle and should we do anything to winterize the hutches? Another option, would be to put them in smaller cages and keep them in the shed (which is metal and uninsulated, though I could run a heater) or bring them into the basement. Any suggestions would be greatly appreciated. Thank you!