3.4.3 Identifying and counting bats in roosts Identification Bats roost in a wide variety of sites within buildings, so the ease with which the bats can be seen is very variable. The horseshoe bats are probably the easiest to identify because they generally hang inaccessible locations and are readily distinguished by size difference. Long-eared bats sometimes hang in obvious locations, often clinging onto timbers near the apex of the roof. However, many of the vespertilionid bats tend to roost in cracks and crevices, often using narrow spaces under soffits or between roofing felt and slates or weather boarding, and so can be much more difficult to see. Always try to keep disturbance of bats to a minimum and spend as little time inside the roost as possible, especially when females are at the end of pregnancy. Some species are very similar and need to be examined in the hand to be certain of the identification. Bats can be caught by hand during the day or by static nets placed outside the exit holes at sunset. When catching at sunset, it is important that a sample of bats is caught at different times because where mixed species are present they can emerge at different times. For example if noctules and Daubenton’s bats roost together the noctules will emerge at least 30 mins before the Daubenton’s. Although identifying live bats is the most accurate way of determining the species present, it can be disturbing and for some species other methods maybe satisfactory, particularly when the bats are absent or inaccessible. Bat detectors in combination with visual clues can be used to identify species leaving the roost, although confidence in identification is restricted to certain species. Where two or more species are present, species can often be distinguished by size, but there is room for confusion between whiskered and pipistrelle bats and between Daubenton’s and Natterer’s bats. A well-used roost may contain mummified corpses or skeletons in the guano pile and these can be identified from a key such as that of Yalden (Other clues to the identity of the bats come from the size, shape and texture of the droppings and the presence of host-specific ectoparasites. Further information about the use of droppings for identification can be found in Stebbings (1993).