DOI: 10.5061/dryad.1ns1rn901
title: Data for: Drivers affecting habitat use in Afrotropical hipposiderid and pteropodid bats

description: Assessing how bats respond to habitat attributes requires an integrative
 approach to reliably predict direct community-level effects. We focused on
 hipposiderid and pteropodid bats because of their diverse resource use
 patterns, body size ranges, and dispersal abilities. We combined an array
 of bat species-level characteristics with key rainforest stand
 characteristics that may covary with habitat use. Twelve stations were
 sampled in the Lomami and Yangambi landscapes in the Democratic Republic
 of the Congo. We investigated whether the species-level flight ability of
 bats and rainforest stand characteristics can affect bat commuting flights
 and community-level estimates of both species detection and habitat
 occupancy. We captured bats for 108 trap-nights. Three sampling events
 (early evening, middle of the night, and early morning) were replicated
 for each survey night. Hipposiderids showed an early evening flight peak,
 while flight activity of pteropodids was constant throughout the night,
 but increased around the middle of the night. Species capture probability
 decreased with higher wing loading in hipposiderids and was negatively
 correlated with higher wing aspect ratio in pteropodids. Forest occupancy
 of hipposiderids increased along the gradient towards waterways, while
 pteropodid occurrence was not directly linked to measured forest stand
 variables. This suggests a consequence of habitat patterns at larger
 spatial scales, which would need clarifying through additional data
 collection. We discuss these findings in terms of resource-use strategies
 of clutter-tolerant and clutter-intolerant species. We argue that the
 occurrence of specific bat species and their habitat use patterns can
 serve as surrogate measures of ecosystem health.
description: The study design tested the status of bats as mobile link
 organisms that can facilitate within-community variation in
 species-specific traits such as mobility, home range, and rainforest
 habitat requirements. This study focused on two bat families,
 Hipposideridae and Pteropodidae. We used a stratified sampling design to
 account for bat community composition, including replication of sites
 across the Lomami and Yangambi landscapes in the Democratic Republic of
 the Congo. We selected two sites per landscape. To capture local
 variation, rainforest stand descriptions and bat surveys were conducted
 using a nested plot design established along transect segments following
 slopes. This design was based on a set of six (20 × 5 m) sampling points,
 hereafter “station”, comparable to a forest stand as a sampling unit. At
 each sampling point, we recorded forest clutter indicators. We recorded
 stem density, including lianas with diameter at breast height (dbh) ≥ 5
 cm, and basal area of woody stems with dbh ≥ 10 cm. We determined the
 Euclidean distance between each sample point and the nearest
 waterways. Bats were captured in Lomami (October
 2018-January 2019) and in Yangambi (October 2019-January 2020). We used
 one set of six traps per station simultaneously. To reduce the effects of
 night time, observer, and trap shyness, we used a rotating survey scheme
 between stations within the site. To fully standardize the trapping
 effort, surveys were repeated at the same station seven days apart during
 different time periods. We used temporal sampling occasions, henceforth
 “event”, as part of the night replication. We fixed the sampling time for
 the fly-out period so that the sampling duration (a 4-h period corresponds
 to one event) was the same for all events per site:  early evening
 (1800-2200 h), middle of the night (2200-0200 h), and early morning
 (0200-0600 h) in Central Africa Time (UTC+0200 h). The total bat survey
 effort was 108 trap-nights (i.e., 3 trap events × 3 replicate nights × 12
 stations). Captured bats were morphometrically measured and released
 unharmed. Recorded data on bats and rainforest stand
 characteristics were pooled at the station level. Bat records from three
 events were combined into a single-season dataset for statistical
 robustness. We built two matrices based on 108 trap-nights for each bat
 family. We evaluated relationships between within-community variation in
 species-specific traits (aspect ratio, wing loading, and potential
 commuting time slots) and capture, separately for hipposiderid and
 pteropodid records (i.e., all 1s for captures and all 0s for no captures).
 Because aspect ratio and wing loading were continuous variables, time
 slots were treated as rank variables with values of 1 (early evening), 2
 (middle of the night), and 3 (early morning). We used wing loading as a
 key determinant of hipposiderid flight behavior and aspect ratio as a
 parameter of pteropodid flight performance to infer commuting flight
 patterns. We simultaneously examined predictors with Bayesian multivariate
 binary logistic regression. We used the <em>wald.test</em>
 function in the <em>aod</em> R package to test for the overall
 effect of time slots on bat captures. We modeled bat capture probability
 distributions over three events with response variables of 1 and
 0. We analyzed repeated presence/absence data from a
 collection of spatial units (stations) over time (events). The model was
 based on the assumption that non-detection (or non-capture) can be
 distinguished from absence through repeated sampling, and that using
 pooled data for all species observed during sampling can improve
 species-specific occupancy estimates. The models built included two
 sub-models, namely an occupancy sub-model and a detection sub-model to
 estimate detection probability to account for imperfect species detection
 and sparse recording. Since this modeling approach requires a fixed list
 of possible species, we generated a species occurrence matrix containing
 the “true” observation state at each station. We included previous
 unpublished data from both Lomami and Yangambi in the analyses to control
 for potential false-negative detections. Species observed at least once
 were assigned an encounter history of 1, otherwise 0 for unobserved but
 previously recorded, to control for false-positive errors in the
 estimates. We created separate matrices for bat species characteristics
 and habitat descriptors. Species-specific covariates were rescaled using
 <em>z</em>-score normalization before running the models to
 facilitate model convergence. Values were back-transformed into their
 original units when discussing model predictions. We fit single-season
 occupancy models with multi-species data (hipposiderids and pteropodids
 separately) using the <em>RPresence</em> package. We included
 species covariates for detection probability and habitat covariates for
 occupancy probability. We estimated the probability of occupancy at a
 given station and the probability of detection (or capture) for each
 species. We selected the most parsimonious model with a change in the
 corrected Akaike information criterion score (i.e.,
 ΔAIC<sub>c</sub> &lt; 2) from a set of candidate models
 with the lowest AIC<sub>c</sub>. Species richness estimates
 were derived from occupancy probabilities.
description: Please see the README document and the accompanying published
 article: Mande C, Van Cakenberghe V, Kirkpatrick L, Laudisoit A, De Bruyn
 L, Gembu G-C, Verheyen E. Drivers affecting habitat use in Afrotropical
 hipposiderid and pteropodid bats. Biotropica, Accepted.
 doi:10.1111/btp.13242