Capture data
Trapping of bats in woodland adjacent to the caves could only be undertaken on a few nights in each swarming season (to minimise disturbance). To obtain sufficient sample size for each taxon, catches were pooled for analysis across 2013-2018. Given that acoustic analysis (Fig 1a & b) shows that the phenology of swarming shifts between years in terms of calendar date, this tends to broaden the apparent seasonal peak in capture rate when capture data are pooled across years, as in Figure 2. Overall, the calendar order of peak swarming activity for each species follows the same order as individually identifiable species detected acoustically (i.e. Daubenton’s > Bechsteins > Natterer’s). The captured sample of Myotis bats showed a strongly male-biased sex ratio, and this male-bias did not vary significantly between years (Table 3).
Table 1: Sex ratios among Myotis bats captured using mist nets and harp traps. Male : female ratios were compared using Fisher’s exact test for sex-ratio bias (null hypothesis of 1:1), and for differences in sex ratio between 2017 and 2018.