Lutra 52(1)_Haarsma & van Alphen_2009

Tubing, an effective technique for capturing pond bats above water

Several bat species, including the pond bat (Myotis dasycneme), long-fingered bat (M. capaccinii) and Daubenton’s bat (M. daubentonii) hunt primarily above water and predominantly use waterways as commuting routes. Researchers capturing such bats for scientific purposes frequently rely on a mistnet placed under a bridge, which is hoisted after each capture. However, capture rates using the hoisting technique tend to be poor, because many bats escape the mistnet while it is being lifted or pass the hoisted mistnet without being captured. Furthermore hoisting raises some bat welfare issues, such as the low visibility of the captured bats and the length of time between capture and release. Our concern for the welfare of the bats and our aim to make capture more effective has led us to design a new technique called ‘tubing’. Tubing consists of a combination of traditional techniques, including hoisting. This article describes the tubing technique and the materials used. It compares the results of the hoisting and tubing techniques during a three year study, involving 134 trapping nights at 154 locations. 868 pond bats of the estimated 1775 flying on these routes were captured during the sessions. The results show a significant difference in capture rate between the two capture techniques, with the tubing technique resulting in a higher proportion of bats being captured than the hoisting technique. This difference was not reduced by the size of the bridge, time of the year, type of waterway or lake. Thus, we argue that tubing represents a more efficient and more ethical technique than hoisting. Other techniques for disentangling bats from a net stretched above water such as using a boat, a chest-wader or trip lines, are also discussed. These are compared with tubing and evaluated for suitability in different environmental conditions, the number of personnel needed and the welfare of bats.