NABat: A top-down, bottom-up solution to collaborative continental-scale monitoring

Abstract

Collaborative monitoring over broad scales and levels of ecological organization can inform conservation efforts necessary to address the contemporary biodiversity crisis. An important challenge to collaborative monitoring is motivating local engagement with enough buy-in from stakeholders while providing adequate top-down direction for scientific rigor, quality control, and coordination. Collaborative monitoring must reconcile this inherent tension between top-down control and bottom-up engagement. Highly mobile and cryptic taxa, such as bats, present a particularly acute challenge. Given their scale of movement, complex life histories, and rapidly expanding threats, understanding population trends of bats requires coordinated broad-scale collaborative monitoring. The North American Bat Monitoring Program (NABat) reconciles top-down, bottom-up tension with a hierarchical master sample survey design, integrated data analysis, dynamic data curation, regional monitoring hubs, and knowledge delivery through web-based infrastructure. NABat supports collaborative monitoring across spatial and organizational scales and the full annual lifecycle of bats.

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

“…acoustic recorders for birds, camera traps for terrestrial mammals), maximize coverage and provide stronger inference about stressor impacts on ecoregion biodiversity (Rich et al., 2019). 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).…”

Audible bats provide opportunities for citizen scientists

“…We also listened for and encountered on one occasion the social calls of the pallid bat, Antrozous pallidus , suggesting that with additional effort this species could also be effectively surveyed using our method. We embedded our survey within the random master sample survey design and analytical framework of NABat (Loeb et al, 2015; Reichert et al, 2021), which added scientific validity and makes our approach scalable across western North America where these and other audible species (e.g., Eumops perotis ; Best et al, 1996) occur.…”

“…Third, sample size, including in both the temporal (replicated within seasons) and spatial dimensions must be large and geographically extensive (e.g., in our case grid cell sample units ideally exceed n = 100 across the broader region of interest, see Banner, Irvine, Rodhouse, Donner, & Litt, 2019) in order to support analytical flexibility and desired inferences (e.g., richer observation process models supported by many within‐season replicates to estimate both false‐negative and false‐positive error). Fourth, multiple coordinating teams (e.g., bat hubs; Reichert et al, 2021) need to collaborate and introduce incentives for public participation in order to establish regional or range‐wide inferential extents and contribute meaningfully to broad‐scale bat ecology and conservation (Callaghan, Rowley, Cornwell, Poore, & Major, 2019; Dickinson et al, 2010). Fifth, clearly‐communicated coordination and data management is essential, and likely requires funding dedicated staff in the coordinating organization (Tulloch et al, 2013).…”

“…We used a portion of central Oregon, U.S., encompassed by two national forest administrative boundaries, to focus our efforts, and overlaid the NABat grid‐based master sample frame (Talbert & Reichert, 2018) with the target region in a Geographic Information System to establish the survey design (Figure 2). The master sample (Larsen, Olsen, & Stevens Jr., 2008; Reichert et al, 2021) provided a spatially‐balanced randomization (Reichert et al, 2021; Stevens & Olsen, 2004) of all grid cell sample units within our study area. Our target sample size was 30 cells, following the master sample randomized rank order to ensure representativeness of the sample (e.g., mean and SD of cliff and canyon grid cell % cover for the sample was similar to the entire 244 grid cell region, 0.075 ± 0.24 vs. 0.084 ± 0.24).…”

Estimating the movements of terrestrial animal populations using broad-scale occurrence data

“…Differences in camera trap survey designs, including baited versus unbaited stations, have been found to have significant consequences for occurrence frequency and detection rates [ 102 , 103 ]. However, there are several examples of such arrays that have been used to infer population movement—acoustic recordings for bat occupancy trends across space and through time [ 104 ], camera traps for raptor prevalence and migration [ 46 ] and migration timing and speed of caribou and ptarmigan [ 105 ]. Although acoustic monitoring is most frequently used to observe species within a local area or during non-movement periods, it has also been used to detect bird populations during migration [ 106 ] or to “catch” the short flight calls that birds emit during migration [ 107 ].…”