Derek, to the bat cave!
Thanks to Derek Coleman and members of the London Bat Group, I was able to join them on one of three winter visits that they undertake to count the bat roost that can be found in two disused tunnels right next to Highgate tube station in north London (above). These Victorian brick tunnels were used by steam trains up until the 1950s and are now boarded up and pitch black inside, save for small caged openings at either end. The floor of the tunnels are a medley of old track, corroded metal and shattered stone, a murderous cocktail without a torchlight to guide us through. The walls have been blackened by soot over the years and age has taken its toll on the mortar - nice hidey holes for the mammals to roost in. There were plenty of experts at hand to explain about bat ecology and the history behind this particular roost.
On a mild day the experts prediction was that the count would be 'in the low-to-mid teens' and they were spot on - we found 15 individual bats, 12 Natterer's and 3 Daubenton's. This was the first time that I had visited any kind of bat roost and enjoyed searching for them in the many nooks and crannies the walls provided.
Above is a photo I managed to grab in torchlight of a Natterer's Bat resting in a specially constructed 'bat brick'. Natterer's was also a lifer - the pan-list gets its 2012 lift-off!