PHENOLOGY OF HIBERNATING BATS
1
THE PHENOLOGY OF HIBERNATING BATS IN CHALK MINES IN WEST SUFFOLK OVER 76 YEARS WITH COMMENTS ON SURVIVAL OF THE DIFFERENT SPECIES ROBERT E STEBBINGS Background In the period following the Second World War, a group of undergraduates, mostly studying at Cambridge University, decided to initiate a study of bats hibernating in two series of derelict chalk mines at Bury St. Edmunds. At that time, there were five chalk pits in Bury with tunnels radiating from the cliffs created in the pits. Their study involved occasional winter visits where the locations of animals were marked on hand drawn plans and soon involved putting numbered aluminium bird rings on the bats’ wings. The first bats were ringed in the 1947/48 winter and continued each following winter. By 1951 the students had dispersed but a local resident of Bury was Owen Gilbert, first a student at Manchester and then Bangor Universities. Because Owen lived away from Bury and became a soil scientist at the then newly formed Nature Conservancy based in Grange-over-Sands, Cumbria, he looked for someone to continue the study. My first visit was on 2 January 1952. At those early times there were few reliable publications detailing knowledge about bats. Those which helped focussed thoughts on what was known and what was unknown, and the evident lack of knowledge helped direct initial studies. Michael Blackmore (1948) and Harrison Matthews (1952) helped by giving advice in person and through their books. At that time there were four known species traditionally visiting the mines for hibernation, Daubenton’s, Myotis daubentonii, Natterer’s, M. nattereri, Whiskered, M. mystacinus and Brown long-eared, Plecotus auritus. I was taught how to distinguish between these. In addition, I was shown how to find, catch and handle the animals and then to apply rings safely. Owen had produced new rings manufactured by Hughes, also bird-style rings with the inscription UCNW Bangor with number (University College of North Wales). East Anglia: Origin of mines in chalk East Anglia is not generally known for its mines. But looking around Suffolk and Norfolk it is obvious many buildings were constructed up to the early twentieth century largely from flint and lime mortar with some brick on corners and around windows and doors. Many of the mediaeval churches, and a few castles, were constructed in this way often with expensive stone sourced from far away, which was used for facing but with a core of flint and mortar in-fill. Walking around the ruins of the Abbey at Bury St Edmunds immediately impresses the fact a large amount of mortar was used in its construction. Thus, there had been local sources for lime which would have been made locally in kilns and transported by horse and cart. Amongst the main areas in Suffolk where chalk out-crops is the north-west of the county including around Bury St Edmunds. It was deposited in warm seas of the early Cretaceous era, roughly around 90–100 million years ago. Traditionally, the chalk was subdivided into three broad units: Lower, Middle and Upper Chalk, with the boundaries marked by hard beds that formed distinctive features in the landscape. Trans. Suffolk Nat. Soc. 59 (2023)