Advanced survey effort required to obtain bat assemblage data in temperate woodlands (Chiroptera)

Abstract

There is a lack of precise guidelines concerning the survey effort required for advanced bat surveys in temperate European woodlands, resulting in a lack of standardisation in survey methods. In this study we assess catch data from 56 bat trapping surveys at 11 UK woodland sites in order to provide recommendations for mist net survey effort required to gain meaningful bat assemblage data in temperate woodlands. Species accumulation curves were produced and were used to develop two novel values for survey effort: the minimum survey threshold (MST), whereby surveyors are more likely than not to encounter less dominant species; and the known species threshold (KST), the point where a given percentage (in our case, 75%) of the known species assemblage for a site is likely to be reached and beyond which there are diminishing returns for survey effort. For our data, the mean of MST was 17.4 net hours, and for KST, the mean was 29.8 net hours. The MST and KST values were reached during the second and third surveys, respectively. These proposed values are adaptable based on location and known species assemblage and may be used for planning advanced bat surveys in temperate woodlands not only to maximise survey efficacy and use of limited resources but to ensure ethical viability of undertaking advanced surveys in the first place.