The dormouse Muscardinus avellanarius has disappeared from a large part of its range in England, probably because of habitat fragmentation and deterioration. Reintroductions, mainly using captive-bred animals, have been generally successful at re-establishing populations within this lost part of the species’ range, with only 2, perhaps 3, out of 15 known to have failed. However, the establishment of new isolated populations is not seen as an end point to the project and attention is now focused on improving habitat connectivity around the reintroduction sites, to enable the founder populations to spread to nearby woods.