The dormouse, a little rodent species you'll find in Britain, hibernate in the winter in nests they hide on the ground. The dormouse spends up to one-third of its life in hibernation, and typically begin that winter "sleep" when the first frost hits, and their food sources are gone.
More on the project's mission here. My first ever theatrical role was as a dormouse in a kiddie production of Alice in Wonderland. I hope my parents have burned all photographs of me in the costume.