The Hazel Dormouse (Muscardinus avellanarius) became extinct in half its former range in the UK during the 20^th century. Captive breeding of dormice began in 1987. The Common Dormouse Captive Breeders Group was set up in 1995 to coordinate breeding for reintroduction into their former range. A national studbook records all dormice held in captivity since 1987; more than 1500 individuals and 214 litters to date. Studbook data were analysed, to examine the relationship between age of breeding female (dam) and various reproductive parameters, to aid captive breeders in maximising production of young, despite limited resources. Maximum recorded lifespan within the captive population is nine years and two months, compared with five years recorded in the wild in the UK. Maximum breeding age of captive dams is five years. Captive dormice produced up to four successive litters in a season. Litter size ranged from 1-9 with four being the most frequent. A dam may be paired with a male for several successive years. There was a decline in both mean and maximum litter size with dam age, and significant variation in the number of young born between sequential litters. The highest mortality rates of young before 30 days of age occurred in those born to five year old dams. To maximise captive breeding potential it is recommended that resources are focussed on breeding using younger dams. More precise and detailed record keeping by breeders for input into the studbook database would aid future analysis.

Captive breeding, dormouse, age, litter size, reproduction

Hazel Joanne Ryan

11th International Dormouse Conference (May 9-13, 2022)