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