Hammer-headed bat movement behavior and habitat selection
Abstract
Background: Animals with key ecological roles, such as seed-dispersing fruit bats, rely to varying degrees on habitat structure to indicate the locations of rewards and risks.
Methods: To understand how variation in vegetation structure influences fruit bat selection, we related movement steps of hammer-headed bats (Hypsignathus monstrosus) to attributes of canopy height, vertical and horizontal structure, and habitat type in a mature rainforest of southern Cameroon. Vegetation structural metrics were measured with UAV-LiDAR at 10 m resolution for a 25 km2 study area. Because bats frequently moved outside the study area, we also characterized vegetation height and horizontal complexity over the full extent of bat movement trajectories by upscaling UAV-LiDAR measurements using spaceborne remote sensing, including GEDI LiDAR data.
Results: At the site level, hammer-headed bats preferred areas of intermediate canopy height close to large canopy gaps (≥500 m). Individual bats varied in selection for vertical vegetation complexity, distance to smaller canopy gaps (≥50 m), and plant volume density of intermediate vegetation strata (10-20 m). Over the full extent of movement trajectories, hammer-headed bats consistently preferred intermediate canopy height, and areas closer to canopy gaps. At both spatial extents, bats moved the shortest distances in swamp habitats dominated by Raphia palms. These behaviors indicate use of forest types that vary structurally, with a preference for open airspace during foraging or moving among resources, and for dense swamp vegetation during roosting and foraging periods. In addition, most bats regularly made long flights of up to 17.7 km shortly after sunset and before sunrise and limited their movements to three or fewer destinations throughout the tracking period.
Conclusions: These results highlight the importance of integrating remote sensing and animal tracking data to understand habitat selection of a species whose movements influence viral spillover risk and spatial patterns of seed dispersal.
Nicholas J. Russo
University of California, Los Angeles
nickrusso@ucla.edu
nicholasrusso@g.harvard.edu
This repository contains the data and code necessary to reproduce the results of Russo et al. (DOI: )
Scripts
Russo_et_al_Bat_iSSA_Dryad_Share.R: Script that produces all analyses and figures included in the manuscript, including:- Sample period of each bat (Fig. S1)
- Integrated Step Selection Analyses (iSSAs) and 95% confidence intervals for covariates at both site-level and landscape scales, including:
- Relative Selection Strength for Canopy Height at site level (Fig. 2A) and landscape level (Fig. 2B)
- Selection for all other structural covariates (Fig. 3)
- Population-level GLMMs at site level (Table 1 summary) and landscape level (Table 2 summary)
- Selection for swamp habitat based on movement step length (Fig. 4)
- Recursive movement analyses (Fig. 5)
Russo_et_al_Bat_UHC_Dryad_Share.R: Script that produces all UHC plots included as supplemental materials in the manuscript
Data folder
Bat Data
Bats2022_2023.csv: Hammer-headed bat GPS locations in UTM coordinates ("x", "y"), along with timestamps ("time") and bat ID ("trackId")
Environmental Layers
ch.tif: Canopy Height, 10 m resolution (site level)vc.tif: Vertical Complexity Index, 10 m resolution (site level)d50.tif: Distance to gap of size >= 50 m, 10 m resolution (site level)d500.tif: Distance to gap of size >=500 m, 10 m resolution (site level)swamp_forest.tif: Landscape classified as either swamp (1) or other habitat (0) (site and landscape level)lai.tif: Leaf Area Index, 10 m resolution (site level)pvd_10_15.tif: Plant Volume Density 10-15 m from the ground, 10 m resolution (site level)pvd_15_20.tif: Plant Volume Density 15-20 m from the ground, 10 m resolution (site level)dist2gapT15_30m_Size_500ha.tif: Distance to canopy gap of threshold height 15 m, max size 500 Ha, 30 m resolution (landscape level)RH95_FINAL_SD_1KM_UTM.tif: Canopy height heterogeneity at 1000 m resolution (landscape level)RH95_FINAL_SD_100M_UTM.tif: Canopy height heterogeneity at 100 m resolution (landscape level)RH95_FINAL_UTM.tif: Canopy height, 30 m resolution (landscape level)
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Session Info:
R version 4.3.1 (2023-06-16 ucrt)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 11 x64 (build 22631)
attached base packages:
[1] parallel stats graphics grDevices utils datasets methods
[8] base
other attached packages:
[1] viridis_0.6.4 viridisLite_0.4.2 ggpubr_0.6.0 glmmTMB_1.1.7
[5] recurse_1.1.2 amt_0.2.1.0 move_4.2.4 raster_3.6-23
[9] sp_2.1-4 geosphere_1.5-18 terra_1.7-39 sf_1.0-14
[13] lubridate_1.9.2 forcats_1.0.0 stringr_1.5.0 dplyr_1.1.2
[17] purrr_1.0.1 readr_2.1.4 tidyr_1.3.0 tibble_3.2.1
[21] ggplot2_3.5.1 tidyverse_2.0.0
