Data from: Male long-distance migrant turned sedentary; The West European pond bat (Myotis dasycneme) alters their migration and hibernation behaviour

Winter survey data, temperature data and mark recapture data of Myotis dasycneme. This study aimed to better understand the migration, mating and hibernation choices of the pond bat. The study area covered the whole of the Netherlands, Belgium and East Frisia (northwest Germany). We defined two study periods, data collected between 1930 and 1980 (Sluiter and van Heerdt) and data between 1980 and 2015 (Haarsma). All available mark and recovery data (ringing) of both the historical and recent migration research were digitized. Observations include location and date of capture, species, sex and ring number. The latest observations in the recent dataset (Haarsma) also include biometric measurements (forearm length, body mass) and information about age and reproductive status. These biometric measurements show that male pond bats are on average smaller and lighter than females (body mass (g)/ forearm length (mm) females: 18.9/47.1, males: 16.4/46.4). The dataset shows changes in the fat mass of both sexes during a year. This study also compares migration data with winter monitoring survey data. We selected winter roosts with three or more records of three or more pond bats in one or both of the study periods. Only data from sites with long-term data series (from the hibernacula in the Dutch provinces of Zuid-Holland, Gelderland and Limburg) were used to analyse trends and annual abundance. Our selection included 59 limestone mines in the province of Limburg and 16 WOII bunkers in Gelderland and 38 in Zuid-Holland. We divided the sites into 'core' and 'satellite' sites depending on the timing of first colonization. Bunker limestone mine microclimate Radiation temperature: radiation temperature of the wall, measured with a non-contact infrared thermometer How many bats: the group size of each bat/ group of bats observed, categorized as alone and group. Where: the hanging location of the observed bat, categorized as hidden (in crevice) or free (free on ceiling or wall) Date: date of the observation Xy-coord: The coordinates of the entrance of the bunker or limestone mine. The RD (Rijks-Driehoek) system is the coordinate system used by the Dutch geographical service. Type: Bunker or limestone Location description: description of the name of the site Bunker monitoring core and satellite Date: date Winter: the period between September and April is defined as the winter of the year starting in January. Location description: description of the name of the site N of pon