Yes, if you're planing to breed them they need to hibernate. About 2 months on 40-50F is sufficient (I use refrigerator successfuly) They should have their guts emptied before you start to lower the temperature (stop feeding them 3-5 days before). Place them in plastic boxes with an inch or two of slightly moist peat or peat moss. You might need to spray them lightly every now and then during the hibernation to keep the substrate moist. If you allow it to dry out, lizards will dehydrate rapidly.