What time of year do hedgehogs hibernate?

They hibernate during the winter. In most cases the males enter hibernation first (and arouse first during the spring), with the females following shortly afterwards. Most hedgehogs will have started hibernation by Christmas, although it varies from place-to-place and can be heavily influenced by the weather/climate and by any supplemental food available to them. In warmer climates, such as those in New Zealand, hedgehogs may forego hibernation altogether and remain active all year.