Data for: Summer declines of cave-dwelling Tricolored Bats
Data files
May 15, 2024 version files 94.50 KB
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README.md
4.69 KB
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TCB_CountData_20230123.xlsx
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Abstract
Several bat species experienced rapid population declines in the northern United States and Canada in response to the white-nose syndrome (WNS) epizootic. The pathogen has since spread across the United States, including the southeast, where relatively warm temperatures may change host–pathogen interactions. In the cave-rich Tennessee-Alabama-Georgia (TAG) region, we examined the impacts of WNS and forest cover on the Tricolored Bat (Perimyotis subflavus) metapopulation using a long-term dataset of 832 cave surveys conducted in summer and winter from 2004–2022. Most bat colonies were small (<30 individuals), and bats were more likely to be present and abundant in caves surrounded by high percent forest cover, reiterating the importance of forest management for bat conservation. When comparing the years before and after the pathogen arrived in 2010–2012, bat presence and abundance during winter hibernation did not change. This stability contrasts significant declines in other studies, suggesting that Tricolored Bat populations respond differently to WNS in small colonies in the TAG region. Fewer Tricolored Bats used caves in the summer than during hibernation, but across all years, we observed 1021 Tricolored Bats in 121 caves during summer surveys. Unlike stable winter trends, bat presence and abundance declined in the post-WNS period in summer, when cave use is optional. This first broad geographical analysis of summer cave use highlights a potentially important change in bat behavior. Disease surveillance and conservation efforts that target caves with relatively small Tricolored Bat colonies in winter and/or summer may be important for regional population persistence of this threatened species.
README: Summer declines of cave-dwelling Tricolored Bats
https://doi.org/10.5061/dryad.c2fqz61j1
This metadata file describes one dataset and one R script file to repeat the analyses for the paper, “Tri-colored Bats persist during winter in caves in the southeastern United States, but summer cave use has declined in response to white nose syndrome”. We conducted all analyses using R version 4.0.0 and RStudio Version 1.3.1073.
*Authors: **Tessa Costley1, Skylar R. Hopkins2, Sophie Meng2, Zachary Gajewski2, and Matthew L. Niemiller1
Affiliations
1 Department of Biological Sciences, The University of Alabama in Huntsville, 301 Sparkman Drive NW, Huntsville, AL 35899
2 Department of Applied Ecology, North Carolina State University, Raleigh, NC 27695
*Corresponding author: Matthew L. Niemiller; e-mail: mn0039@uah.edu
R Script File: TriColoredBat_Analysis.R
This R script loads one data file: TriColoredBat_CountData.csv (see below). These data are used to quantify how Tri Colored Bat presence and abundance changed from before to after the WNS epizootic in summer and winter. It also quantifies how forest cover data affected bat presence and abundance. The script is used to make all the figures from the paper.
Dataset: TriColoredBat_CountData.csv
Overview: This CSV file contains data from cave surveys in Tennessee, Alabama, and Georgia before and after the fungus that causes white nose syndrome invaded the region. Each row in the dataset represents a survey of a particular cave; some caves were surveyed more than once and are thus represented by multiple rows in the dataset. The columns in the dataset describe the caves that were sampled (e.g., ecoregion, elevation), the specific survey (e.g., date), and the number of bats observed during the survey.
Description of columns:
Cave_no: A unique identification number given for each cave. Due to the sensitive nature of cave data, our dataset refers to caves only by cave number and county. Individual descriptions, maps, and locations of cave systems are maintained by the Tennessee Cave Survey (TCS; http://www.subworks.com/tcs/), Alabama Cave Survey (ACS; http://www.alabamacavesurvey.org/), and Georgia Speleological Survey (GSS; https://caves.org/survey/gss/GSSWebsite/Home.html).
TCB_obs: The number of Tri Colored Bats observed during the cave survey.
sur_length: The total length in meters of the cave passage that was surveyed. This variable was used to correct for sampling effort (and to create a bat density variable), because caves vary in size and some areas within caves are not accessible to researchers (units = meters).
Date: The date of the survey.
WNS: Whether the survey took place before the fungus that causes WNS was present in the region (PRE) or after the fungus that causes WNS was present in the region (POST).
State: The state where the cave was located: AL, GA, or TN.
County: The county where the cave was located.
Grey Bats: Whether endangered Grey Bats were present in the cave during the survey.
Elevation: The elevation in meters of the cave entrance.
Geol_Formation: The geological formation where the cave was located.
L4_Ecoregion: The Level 4 Ecoregion where the cave was located.
L3_Ecoregion: The Level 3 Ecoregion where the cave was located.
season: Whether the cave was surveyed during the 16 October to 14 April hibernation season (“Winter”) or outside of the hibernation season (“Summer”).
wyear: The working year during which the survey occurred. Because winters cross two years (e.g., Fall 2019 and Spring 2020), winters are numbered by the year during the spring survey (e.g., Fall 2019 surveys occurred in wyear 2020).
closest_year: The closest year to the survey date where forest cover data were available. The USGS Global Forest Cover Change image collection only contains satellite imagery data for 2000, 2005, 2010, and 2015. So, for example, surveys from 2014 used forest cover data from 2015.
closest_tcc_1500: Within a 1500 m (radius) buffer around the cave, the percent of pixels in 30x30m units that were designated as woody vegetation above 5 meters in height by the USGS Global Forest Cover Change image collection (units = % pixels).
closest_tcc_11400: Within a 11400 m (radius) buffer around the cave, the percent of pixels in 30x30m units that were designated as woody vegetation above 5 meters in height by the USGS Global Forest Cover Change image collection (units = % pixels).
Methods
A total of 466 caves and 832 visual surveys were conducted throughout Tennessee, Alabama, and Georgia. These caves varied across five level III ecoregions, latitude, and elevation. Caves were not selected based on previous WNS data, but on having little to no previous biological data or were associated with other focal taxa. Comprehensive visual surveys from the cave entrance to the farthest explorable area by the research team were conducted year-round. When encountered, all bats were identified visually by an individual on the team with bat identification experience. During the surveys, the survey length was recorded as a linear measurement from the cave entrance to the survey stopping point. Forest cover around the cave was collected using satellite imagery from the USGS Global Forest Cover Change image collection. The proportion of forest cover was defined as the percentage of pixels in 30x30 m units designated as woody vegetation >5 m in height within a circular buffer from the cave entrance used for the survey. This was done for two different buffer zones around the cave entrance, 1500m and 11,400m. The image collected ran from 2000-2015 and had images every five years, therefore, the closest image to the survey date was used to quantify percent forest cover.