Data analysis
We used ArcMap v. 10.3 (ESRI 2014) to construct Minimum Convex Polygons (MCPs) based on all the points we recorded for each individual (i.e., night range; NR hereafter) and for points recorded when we observed the bats singing (i.e., singing range; SR hereafter). We calculated Kernel Density Estimates (KDEs) for NR and SR, as well for points recorded during the early portion of the night (~20:00–23:00; ER hereafter) and the late portion of the night (~0:00-3:00; LR hereafter). We calculated the KDEs using Geospatial Modeling Environment v. 7.4.0 (Beyer 2015) for each individual with greater than 30 points recorded over the course of our surveys (Amelon et al. 2009). Prior to creating our KDEs, we subsampled the times that bats spent at their perches by 2-min intervals because individuals could easily cross the approximate boundaries of their territories within this time period. Finally, we calculated the area of 50% and 95% probability isopleths of each NR, SR, ER, and LR KDE (Millspaugh et al. 2012). We identified the centroids of the 50% KDE and calculated the percent overlap of adjacent 50% KDEs. We compared the size of NR and SR MCPs, and NR, SR, ER, and LR KDEs using matched-pair t-tests and Wilcoxon signed-rank tests. We examined spatial shifts in the areas used by comparing the locations of centroids using Hotelling T2 tests. Finally, we used the intersect tool in ArcMAP to calculate 2-dimensional overlap of KDEs between neighbors.
We calculated the average amount of singing per night for each individual, the time each individual spent singing per hour averaged across nights, and the proportion of time individuals spent singing at each perch. We used repeated-measures ANOVA and post-hoc matched-pair t-tests to test for differences in the mean time bats spent singing per hour and Welch’s ANOVA to singing amounts across individuals. We compared early vs. late night singing, and number of singing vs total perches used with matched pair t-tests. We used Pearson’s r and Spearman’s ρ to examine correlations between mean nightly singing amount and number of perches used, maximum amount of singing per perch, range sizes, and morphometric data.
RESULTS