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 A good crowd of members gathered at the Methodist Church on April 22nd for a talk given by John Puckett, chairman of the Kent Bat Group. John began by explaining that there were 17 species of bat native to Britain. They are long-lived (a serotine specimen in Kent was known to have lived for 16years) are social animals, and the only mammals that fly. Bats are warm-blooded, and flying consumes much energy, so bats tend to cluster together to conserve warmth. Females group together in maternity roosts, where the young are born, naked, around June. They are fed on milk until they are able to fly. All bats in Britain eat insects, and all therefore need to echo-locate. The sound-processing area of a bat’s brain is enlarged: the creatures clearly hear a detailed ‘sound picture’ that we humans cannot even imagine. As winter approaches, bats build up their fat reserves. There are few insects about in the cold season, so they hibernate. A humid, sheltered location that is not freezing is needed, and several species seek out caves for this. Culverts, ice-houses, bridges, quarries and old air raid shelters are also used. Research has shown that a bat’s heart rate can drop from 800 to 15 beats per minute, and the metabolism just ‘ticks over’ during hibernation. Water loss is a potential problem, so a spot with a suitably high atmospheric humidity is also sought.
Dene holes – vertical shafts with side-galleries once used for extracting chalk – are common in Kent, and favoured by several bat species. Studies at one in Dadmans Shaw in our parish, have shown that the air temperature near the ceiling in the deep galleries remains at 8 degrees C throughout the year: ideal for a winter snooze! This particular dene hole ranks as one of the most important in Kent for several species of bat.
Work in association with the University of Leeds, involving analyses of the DNA from fur, combined with radio-tracking, demonstrates that bats can travel up to 60km per night. Such studies are revealing more about bat behaviour, and may shed light on the serious problem of why numbers are declining. But the reason why some species regularly ‘swarm’ in the autumn, remains a mystery for now.
John completed a fascinating, well illustrated, talk by describing some of the challenges of studying bats as they roost in inaccessible places, and creating new roosts for them. In a final flourish, he showed members a tiny live pipistrelle that was ‘in care’ and recovering from a damaged wing.
Bob Baxter
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