A meeting with strangers at a gateway on a footpath generates nervous conversations. Ours consisted of tame jokes about batmobiles and accomplices called Robin. We were waiting for the "bat man" who was to be guide on our night-time walk. The objective was to encounter Britain's flying mammals in the company of someone who knew something about them. When Batman arrived he was carrying a box, like an oversized personal stereo, which (he explained) would enable us to hear the bats and identify what and where they were.
I last heard bat noises when, as a small boy from London, I took a twilight walk with my parents during a holiday in the country. The ultrasounds bats use for echo-location may be just about audible to a child, but are well above the range that adult hearing can perceive. Our Batman used simple technology to slow the sounds down to an audible range. The first hint of activity came in the form of regular single bleeps that became more frequent as the creature focused on obstacles of prey. It was a Noctule, Britain's largest bat and generally the earliest riser - appearing as twilight gives way to darkness. "Largest" in this context does not mean very big, because all our bats are tiny creatures. The biggest Noctules have a head and body length no greater than 82mm (3 ¼").
Our most common bats are the Pipistrelles (actually 2 species) with head and body length of up to 45mm (1 ¾") and small enough to fit into a matchbox. Their sounds were the next to excite Batman's machine, which now emitted streams of rapid high-frequency noises that rose and fell as the bats wheeled around us. The accuracy of their echo-location guarantees that they would never collide with us, but a few of our number kept ducking to make sure! It is a strange experience 'watching' wildlife through sound pictures, but the occasional sighting enhanced the picture as one of the bats wheeled in the direction of the now-retreated sun and became silhouetted against the not-quite-dark sky.
Our walk took us through the local housing estate, with not a single belfry in sight. That was another preconception destroyed as Batman explained that bats prefer to nest in trees or modern lofts, rather than the dusty roofs of ancient churches. They are common in modern houses, with the owners often completely unaware of their presence. A few crumbly droppings within the roof space might give their presence away, but they are unlikely to be visible as their tiny bodies can squeeze into the smallest crevices. In any case, their domestic residence generally only covers their brief summer brooding period and winter hibernation is more likely to take place in hollow trees.
Our third bat encounter that night was heralded by a regular sound pitched midway between the sonorous (in bat terms) Noctule and the Pipistrelle descant. The source of the sounds was over the lake, flitting low above the water to catch its favourite water-loving insects. This was Daubenton's bat, a little larger that the Pipistrelle and somewhat less common. Batman explained that we have sixteen native species of bat in Britain, though some of them have become extremely rare.
Rarity is an increasing problem for bats as our environment-changing lives have diminished their habitats and reduced their supply of insects to feed on. All of Britain's bat species live on insects, as do three-quarters of the 1,000 bat species that inhabit the rest of the world. Nectar, pollen and fruit figure as important food sources to many other bat species and a notorious few feed on blood (but, hey, what do you suppose puts the redness into the red-meat humans eat?). Bat conservation groups seek to preserve Britain's remaining bats, which are legally protected in this country.
The Batman jokes had ceased by the time we wandered back along the dark paths to the gateway where we had assembled. Unlike other rambles I have been on, I will not remember the faces of the people I walked with that night. But I recall the absorbed excitement in their voices as the mysteries of these creatures of the night were recounted as they flitted around us. They don't have the visual brilliance of butterflies or the singing abilities of birds, but bats are interesting enough to merit the occasional late night walk.