A plan for the North American Bat Monitoring Program (NABat)

Loeb, Susan C.; Rodhouse, Thomas J.; Ellison, Laura E.; Lausen, Cori L.; Reichard, Jonathan D.; Irvine, Kathryn M.; Ingersoll, Thomas E.; Coleman, Jeremy T. H.; Thogmartin, Wayne E.; Sauer, John R.; Francis, Charles M.; Bayless, Mylea L.; Stanley, Thomas R.; Johnson, Douglas H.

doi:10.2737/srs-gtr-208

Cited by 108 publications

(99 citation statements)

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“…This study reinforces the value of broad‐scale acoustic monitoring efforts and their ability to detect change at broad spatial scales between years (Barlow et al., 2015; Loeb et al., 2015; Neece et al., 2018; Rodhouse et al., 2019). Although our study was at a large scale relative to other agriculture studies, we were confined to a highly modified agricultural region, and the effects of agriculture on bats need to be investigated at broader spatial scales, inclusive of a broader variety of habitat types.…”

Section: Discussionsupporting

confidence: 81%

“…Continuous monitoring would allow wildlife agencies to measure population trends and employ a dynamic occupancy modelling framework to determine extinction and colonization probabilities (Neece et al., 2018; Rodhouse et al., 2015). The grid we deployed was substantially smaller than recent broad‐scale bat monitoring efforts (Barlow et al., 2015; Loeb et al., 2015; Neece et al., 2018; Rodhouse et al., 2012); however, we found limited evidence of spatial autocorrelation. Our finer grid allowed us to integrate our data collection with other sensor‐based survey methods (e.g.…”

Section: Discussionmentioning

confidence: 58%

“…We recommend that researchers weigh their specific data collection needs during the study design phase (Reichert et al., 2021), but acknowledge that broad‐scale deployments (e.g. NABat grid‐based master sample) may reduce spatial autocorrelation caused by bat movement and allow for a more robust interpretation of occupancy (Loeb et al., 2015).…”

Section: Discussionmentioning

confidence: 99%

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Insectivorous bat occupancy is mediated by drought and agricultural land use in a highly modified ecoregion

Smith

Furnas

Nelson

et al. 2021

Diversity and Distributions

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Aim California's Central Valley, one of the most productive agricultural regions worldwide, is home to a high number of at‐risk species due to habitat conversion. Amplifying the issue, the Central Valley faces severe droughts, creating water scarcity in surrounding natural areas. At least 14 insectivorous bat species live in this region, and prior studies show mixed results regarding the impact of agriculture and drought on bats. The aim of this study was to investigate how bats use agricultural areas during drought. Location Central Valley, California, United States. Methods We deployed ultrasonic acoustic detectors at 274 sites from March through July of 2016, the final year of an extreme drought, and 2017, one of the wettest years on record. We identified bats to species, used single‐species occupancy models including biologically relevant covariates and created spatial projections of ecoregion‐wide occupancy for each species. Results We modelled occupancy for eight bat species. Long‐distance migrants in the study area contracted their geographic range during the drought, while resident species did not. Five of the eight bats in this analysis were more likely to occupy areas with orchard crop cover. Lastly, arid‐adapted bats used cultivated landscapes during the drought but retracted their range after the drought ended. Main conclusions Migratory bats appeared to shift occupancy more during drought than resident bats, possibly because of lower roost fidelity. Additionally, the effects of drought on some bat species in the Central Valley may be buffered by agricultural landscapes acting as drought refugia. Overall, this study demonstrates the benefits of broad‐scale acoustic studies which can serve as a tool to track changing bat distributions on the landscape and provide baseline occupancy for acoustically detectable species.

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 58%

Section: Discussionmentioning

confidence: 99%

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Insectivorous bat occupancy is mediated by drought and agricultural land use in a highly modified ecoregion

Smith

Furnas

Nelson

et al. 2021

Diversity and Distributions

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“…This work has important implications for how we survey bat populations-namely that partial-night surveys may not capture a representative sample of the local bat assemblage. It is a common practice in mist-net and driving transect surveys to exclusively sample the first 1-5 hr following sunset (Loeb et al, 2015;U.S. Fish & Wildlife Service, 2020).…”

Section: Discussionmentioning

confidence: 99%

Bats partition activity in space and time in a large, heterogeneous landscape

Beilke

Blakey

O’Keefe

2021

Ecology and Evolution

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Diverse species assemblages theoretically partition along multiple resource axes to maintain niche separation between all species. Temporal partitioning has received less attention than spatial or dietary partitioning but may facilitate niche separation when species overlap along other resource axes. We conducted a broad‐scale acoustic study of the diverse and heterogeneous Great Smoky Mountains National Park in the Appalachian Mountains. Between 2015 and 2016, we deployed acoustic bat detectors at 50 sites (for a total of 322 survey nights). We examined spatiotemporal patterns of bat activity (by phonic group: Low, Mid, and Myotis ) to test the hypothesis that bats partition both space and time. Myotis and Low bats were the most spatially and temporally dissimilar, while Mid bats were more general in their resource use. Low bats were active in early successional openings or low‐elevation forests, near water, and early in the evening. Mid bats were similarly active in all land cover classes, regardless of distance from water, throughout the night. Myotis avoided early successional openings and were active in forested land cover classes, near water, and throughout the night. Myotis and Mid bats did not alter their spatial activity patterns from 2015 to 2016, while Low bats did. We observed disparate temporal activity peaks between phonic groups that varied between years and by land cover class. The temporal separation between phonic groups relaxed from 2015 to 2016, possibly related to changes in the relative abundance of bats or changes in insect abundance or diversity. Temporal separation was more pronounced in the land cover classes that saw greater overall bat activity. These findings support the hypothesis that niche separation in diverse assemblages may occur along multiple resource axes and adds to the growing body of evidence that bats partition their temporal activity.

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“…Balancing trade‐offs is a challenge in monitoring design, especially for rare species that are found in large and remote landscapes. Recent research has suggested passive survey devices, such as remote cameras or acoustic recorders, can provide multispecies trend information (e.g., Kays et al 2009, Furnas and Callas 2015, Loeb et al 2015, Steenweg et al 2018, Wood et al 2019 a ). We caution that while such methods can be used to obtain detections of different species, it is likely that for each species, each device has a different effective area and therefore effective multispecies trend monitoring becomes much more complicated.…”

Section: Discussionmentioning

confidence: 99%

Effective sampling area is a major driver of power to detect long‐term trends in multispecies occupancy monitoring

et al. 2021

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Occupancy-based monitoring has become an important tool in wildlife conservation and management. Nonetheless, meeting occupancy modeling assumptions and providing biologically accurate information are difficult tasks over long time periods, large areas, or when monitoring multiple species. In occupancy modeling frameworks, derived grids are commonly used to divide landscapes into discrete units. Grid sizes that match the home range size of the species of interest are considered optimal, but this practice is complicated as home range size may vary by sex, habitat quality, or among species. Additionally, studies often assume their survey methods sample an entire grid cell when the actual effective sampling area may be much smaller. The effect of reduced effective sampling area on occupancy estimation has received little attention to date, despite being flagged as a critical issue. In this study, we assessed (1) how the relationship between effective area, home range size, and grid size affects power to detect trends in occupancy; (2) how varying the sampling design factors of effective area, duration, detection probability, and resurvey interval influence monitoring efficiency; and (3) determine whether a single sampling design can simultaneously detect declines in two species with different home range sizes. We used a spatially explicit simulation framework to create biologically realistic declining populations over 10 yr and assessed statistical power to detect known declines using occupancy modeling. We found that effective area and detection probability had the greatest influence on statistical power. We could not reliably detect declines when detection probability was low or when effective sampling area was <1/4 cell. We conclude that failing to account for effective area less than the cell size will result in overestimation of statistical power. Our simulations suggest occupancy models can detect declines for two species with different home range sizes using the same grid cell size under certain conditions, for instance, surveying >25% of the landscape, ≥25% effective area, and fixed sampling locations. Further, increasing resampling interval greatly increased monitoring efficiency. Our results show monitoring planning requires explicit consideration of effective sampling area and methods with sufficient detectability to detect population declines.

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A plan for the North American Bat Monitoring Program (NABat)

Cited by 108 publications

References 0 publications

Insectivorous bat occupancy is mediated by drought and agricultural land use in a highly modified ecoregion

Insectivorous bat occupancy is mediated by drought and agricultural land use in a highly modified ecoregion

Bats partition activity in space and time in a large, heterogeneous landscape

Effective sampling area is a major driver of power to detect long‐term trends in multispecies occupancy monitoring

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