Dormice (Family Gliridae) are rodents that appear similar to mice physically, with a major visible difference being a furred tail, rather than the 'scaly' tail of mice or rats. They mainly inhabit Europe, but some species' ranges extend into Western Asia and Africa. Dormice are known for their hibernation habits - they hibernate even in temperate regions up to 6 months of the year, depending on species. Their diet consists largely of nuts and fruits, but they are also known to each insects and other invertebrates. Some species are mostly arboreal - living in trees, as opposed to on the ground like mice.
In the Book series, dormice are mentioned as a food items for the Romans. In fact, historic Romans did eat the Edible Dormouse (Glis glis) as a delicacy for wealthy individuals. Their fat as said to aid with sleep, due to their ability to hibernate. Dormice were in such demand, that Romans would raise dormice in a special terracotta jar with air holes and small shelves on the inside. These were called Glirarium. Dormice were locked into the jar in darkness with food such as dried fruit and nuts which would induce the dormice to fatten up in preparation of hibernation. One recipe calls for fattened dormice doused in honey and coated with poppy seeds.
The Fat Consul is again mentioned eating dormice at the gladiatorial event of Saturn's Day Saturday, this time a "light snack of double reptoburger with tomato-and-dormouse relish and popdragons on the side."