NATURE COLUMN: Bill Cawley

I AM told that the urgent and badly needed repair to the roof of the Big Mill has been delayed because bats have been discovered in the upper rooms of the listed building. The developer has now to get a bat licence to remove the tiny mammals before the work can be continued.

I do not know whether the bats are pipistrelle or larger species as bats can be difficult to identify, appearing on the edge of sight as a flickering, darting presence. The larger bats that fly as high as swifts on summer evening are probably noctules and the small fast flying ones are pipistrelle even though since the late 1990s this commonest of bats is now split into two distinct types based on the frequency of their calls. This diminutive creature is voracious and can consume up to 3,000 insects mostly small flies and midges in one night. In country areas it is well named as the “flitter mouse”.

The building work at the Big Mill may have a secondary effect as Dave, who attends the same gym as I do, and lives in Mill Street, told me of the increase in bats flying around his garden almost certainly displaced from the landmark building close by.

Bats use sound to locate their prey which is why they can feed in complete darkness. To determine what bat is you require a detector which converts the high pitched squeals into sound that humans can hear.

In Leek there are a few species that exist in area. One early autumn evening in 1997 I participated in a bat walk around Brough Park. It was a warm early September night and all the local types were present. Pipistrelle, those impish creatures of the dusk, with their jerky flight were the most visible. Noctules appearing as the light faded were noticeable by their steep plunging dives as they hunted and the horse shoe bats with their large ears sensitive to artificial light were flying low to catch insects on the ground or on low vegetation.

In the winter time pipistrelle do not sleep continually, but emerge on hunting forays on close evenings in search of insects.

The larger bats hibernate through the winter hanging by curved claws in the draughty holes of trees or semi- derelict buildings unprotected except by their wings which are wrapped around their bodies for warmth.

In anticipation of a long winter the bat gorges well in the preceding months to build up stores of fat. In the darkness of the season the vital organs close down to a minimum, the heart beat slows down and life is reduced to a flicker.