Development of the Captive Breeding Programme for the Re-introduction of Hazel dormice (Muscardinus avellanarius) in the United Kingdom, 1982-1994

In 1981 the lead author wished to instigate a breeding programme for an indigenous and endangered British mammal species that was known to have suffered a significant decline in numbers. Captive breeding to provide individuals for potential re-introductions was considered the most appropriate approach to helping the re-establishment of wild populations from where they had previously been lost or declined. The selected species needed to be harmless to the environment and small so that expensive techniques were not required. The intention was to generate a sufficiently large and genetically diverse captive population which would supply a formal re-introduction programme into appropriate sites. Having addressed the reasons for previous declines of local extinction, released dormice would provide the basis for new populations. Given the resources available, the Common or Hazel dormouse, Muscardinus avellanarius was considered to be a suitable species for this programme. Successful captive breeding had not been achieved previously. The Mammal Society Dormouse Survey 1975–79 demonstrated it had been lost from seven counties in the UK during the previous 100 years [1]. A nocturnal and secretive species little was known about the detailed dietary requirements or behaviour of the common dormouse. The establishment and development of the breeding colony enabled observations of their nocturnal activity in captivity. This was observed at very close quarters and behaviour related to feeding, mating, juvenile development and other seasonal changes in activity was noted. Initially there were numerous juvenile deaths within the colony, usually in spring and autumn but with changes to the temperature regime immediately prior to and post hibernation, this mortality reduced. By 1992 the numbers in the captive breeding colony grew to 33 individuals, sufficient for the first trial re-introduction of 11 individuals to take place in Hertfordshire following the IUCN guidelines [4]. Following further breeding and survival success, further re-introductions were supported and by 1995 the colony had risen to 97 individuals. In that year the Common Dormouse Captive Breeders Group was formed and currently six dormouse breeders in the group donate individuals each year to re-introduction projects, supervised by The People's Trust for Endangered Species.