Lutra 52(1)_Haarsma & Tuitert_2009

An overview and evaluation of methodologies for locating the summer roosts of pond bats (Myotis dasycneme) in the Netherlands

During a long-term and intensive study in various parts of the Netherlands we employed five survey methods to find pond bat (Myotis dasycneme) roost sites: church loft inspections, telemetry, tracking back commuting routes, searching for swarming and involving the public through using questionnaires or requests for information about roosts in newspapers. In this paper we aim to help improve the effectiveness of survey methodology by presenting a description of the materials needed for each method, the optimal timing and duration and practical tips. Each of the methods employed provided different results in terms of the effectiveness, selectiveness and efficiency in finding roosts. To review the efficiency of a method, we calculated the number of days of preparation and research needed to find one new roost. On average church loft surveys took 43.5 days to find a new roost, telemetry 7 days; tracking back 7 days; and swarming 9.4 days. Each method has specific requirements; such as experience, specific material and licence. It is always wise to consider the feasibility of a method and the most appropriate method for ones’ goal and the given moment in the bats’ life cycle. This said, all kind of combinations of the methods described can be made.