Context

Conservation for the Indiana bat (Myotis sodalis), a federally endangered species in the United States of America, is typically focused on local maternity sites; however, the species is a regional migrant, interacting with the environment at multiple spatial scales. Hierarchical levels of management may be necessary, but we have limited knowledge of landscape-level ecology, distribution, and connectivity of suitable areas in complex landscapes.

Objectives

We sought to 1) identify factors influencing M. sodalis maternity colony distribution in a mosaic landscape, 2) map suitable maternity habitat, and 3) quantify connectivity importance of patches.

Methods

Using 3 decades of occurrence data, we tested a priori, hypothesis-driven habitat suitability models. We mapped suitable areas and quantified connectivity importance of habitat patches with probabilistic habitat availability metrics.

Results

Factors improving landscape-scale suitability included limited agriculture, more forest cover, forest edge, proximity to medium-sized water bodies, lower elevations, and limited urban development. Areas closer to hibernacula and rivers were suitable. Binary maps showed that thirty percent of the study area was suitable for M. sodalis and 29% was important for connectivity. Most suitable patches were important for intra-patch connectivity and far fewer contributed to inter-patch connectivity.

Conclusions

While simple models may be effective for small, homogenous landscapes, complex models are needed to explain habitat suitability in large, mixed landscapes. Suitability modeling identified factors that made sites attractive as maternity areas. Connectivity analysis improved our understanding of important areas for bats, identified suitable patches that may be isolated from the habitat network, and prioritized areas to target restoration.

Cable_et_al_env_data.gdb

Land cover environmental data (e.g., total area of forest in 500-m radius) were derived from the "Land cover of Illinois 1999-2000" (IDNR 1999). The original dataset was resampled from 30-m to 100-m resolution. The classes were simplified into major (forest, water, urban, agriculture, grassland, and other) and minor classes (bottomland forest, coniferous forest, and deciduous forest). Total area, total edge, and the number of patches were computed in FRAGSTATS using moving window analyses (100-m, 500-m, and 1-km window sizes).

Distance to water was calculated in ArcMap 10.6.1 (ESRI) using the water area shape files from the National Hydrography Dataset (USGS 2018). Distance to major roads was calculated using the Illinois Department of Transportation road data (IDOT 2017). We calculated the distance from roads that receive an average daily traffic rate of >2 cars/minute.

Original data citations:

Illinois Department of Natural Resources, Illinois Natural History Survey, Illinois State Geological Survey, Illinois Department of Agriculture, United States    Department of Agriculture National Agricultural Statistics Service (1999) 1:100,000 Scale. Land Cover of Illinois 1999-2000, Raster Digital Data, Version 2.0, September 2003 https://clearinghouse.isgs.illinois.edu/data/land-cover/land-cover-illinois-1999-2000-data Accessed 4 October 2018

Illinois Department of Transportation (2018) Illinois roads, shape file data https://apps.dot.illinois.gov/gist2/ Accessed 4 October 2018

U.S. Geological Survey (2018) National hydrography dataset https://www.usgs.gov/core-science-systems/ngp/national-hydrography/national-hydrography-dataset?qt-science_support_page_related_con=0#qt-science_support_page_related_con Accessed 4 October 2018

Cable_et_al_outputs.gdb

We created suitability maps by modeling Myotis sodalis maternity habitat in MaxEnt. We binarized models based on the 10% suitability threshold in our training occurrence data. We used the Raster to Shapefile tool in ArcMap 10.6.1 to generate the suitable areas shapefile.

We calculated patch importance for habitat connectivity for each suitable area polygon in Conefor Sensinode 2.6. The isolated suitable areas shapefile represents suitable areas that are only important for intra-patch connectivity and not inter-patch connectivity. These methods are explained in detail in "Habitat suitability and connectivity modeling reveal priority areas for Indiana bat (Myotis sodalis) conservation in a complex habitat mosaic."

We created the priority restoration areas shapefile by buffering Myotis sodalis hibernation sites by 125 meters and buffering suitable habitat patches by 10.1 km. We intersected the two buffers to create the layer. Myotis sodalis occurrence locations cannot be shared due to federal restrictions.

Cable_et_al_env_data.gdb

Variable naming:

ta = total area

te = total edge

np = number of patches

dist = distance to a feature

100 = 100-m radius

500 = 500-m radius

1 = 1-km radius

for = forest

wat = water

bot/bottomland = bottomland forest

conif = coniferous forest

ccd = closed-canopy deciduous forest

ag = agriculture

urb = urban

(e.g., ta_for_100 is total area of forest in a 100-m radius; np_wat_1 is number of water patches in a 1-km radius)

null is a raster with values 1-100 randomly distributed across the landscape

Resolution:

100-m x 100-m cells

Coordinate System:

NAD_1983_UTM_Zone_16N

Datum:

NAD_1983

Other:

ASCII format

3415 columns, 6190 rows

Cable_et_al_outputs.gdb

Suitable_areas are polygons that are suitable as determined by our MaxEnt habitat suitability models

Conefor_patch_metrics is a table of the connectivity importance values for each suitable patch. One could join the table to the shapefile for visualization.

Isolated_suit_areas are polygons that are only important for intra-patch connectivity, thus are more isolated from the Myotis sodalis maternity habitat network

Priority_restoration_areas are areas that are within 125 km from a known hibernaculum and also within 10.1 km of a suitable area for Myotis sodalis