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.