IVth International Conference on Dormice (Rodentia, Gliridae)13 - 16 September 1999 EDÝRNE - TURKEY |
STUDIES OF THE EDIBLE DORMOUSE, GlIS GLIS, IN ENGLAND.
Morris, P. A.
School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX UK, e-mail: p.morris@rhbnc.ac.uk
This paper describes recent developments in a long-term study of Glis ecology. Nest boxes have proved attractive to the animals and allow monthly monitoring of dormice throughout the summer. Wooden nest boxes are costly, so an inexpensive plastic “nest tube” has also been used successfully. Nest boxes and nest tubes provide data on Glis numbers and breeding. No young were found earlier than August, suggesting that only one litter can be reared successfully each year. Litter size varied from 1-10 young, but numbers were related to body mass, implying loss of individuals from larger litters. The smallest independent young weighed 67g. No litters of more than 5 babies exceeded 60g mean weight per individual, suggesting that females may normally only rear 4-5 young to independence.
In 1997, animals were abundant in nest boxes in September and October, several even as late as November. Yet in 1998 there were no animals present in October and only one in November. Many nestlings were found in nest boxes in 1997, but only 2 in 1998 and none in 1996. This suggests major inter-annual variation, particularly in production of young, which was also reported from Germany during 1996.
Animals larger than about 90g were individually marked with PIT tags to monitor individuals throughout their life. Using a protocol based on body weight, a likely birth year was assigned to each of the 134 animals marked so far. At least 65% of young survived into their second year, 25% to their third year and a few lived more than 5 years. Actual survival may be considerably longer as this study only began in 1995, and there has been insufficient time for animals to live to a very old age. However, these calculations are crucially affected by the arbitrarily selected body weights used to assign animals to birth years.
The size frequency distribution in October (ie at the end of the breeding season) is clearly bimodal. The largest apparent young of the year weigh 120g, but is it possible to achieve this weight by October when young appear not to be born before August? Following the growth of 11 known individual nestlings for up to 24 days shows a mean growth rate of 1.7g per day. A crude estimation suggests that a weight of 50g could be attained in a month, and 120g is possible within the first summer (although probably not more) provided that the season is not curtailed by early hibernation.
In September 1997, nine adults were radio tracked. Home ranges were small (about 0.2ha per night; cumulatively 1-2ha after 12 nights) and overlapping. The hibernacula were located, all underground about 30cm beneath the surface, in firm soil and contained no nesting material. Access was often via rotted-out tree roots. Temperature loggers were installed but failed to record hibernation behaviour. In autumn 1998 two captive animals were induced to hibernate in simulated natural conditions. Three methods of temperature recording were used. Arousals occurred throughout the winter. Hibernation bouts averaged 7.7 days overall, shorter (about 4 days) in early and late winter, associated with more frequent arousals at these times.