Variation in regional and landscape effects on occupancy of temperate bats in the southeastern U.S

Habitat Associations of Overwintering Bats in Managed Pine Forest Landscapes

Research Highlights: Seasonal variation in environmental conditions coinciding with reproductive and energetic demands might result in seasonal differences in species-specific habitat use. We studied a winter assemblage of insectivorous bats and found that species acted as habitat generalists during winter compared to expectations based on the summer active season. Background and Objectives: In temperate regions, seasonal fluctuations in resource availability might restructure local bat assemblages. Initially perceived to only hibernate or migrate to avoid adverse winter conditions, temperate insectivorous bats appear to also employ intermediate overwintering strategies, as a growing body of literature suggests that winter activity is quite prevalent and even common in some lower latitude areas. However, to date, most studies have exclusively assessed habitat associations during summer. Because habitat use during summer is strongly influenced by reproduction, we hypothesized that habitat associations might differ during the non-reproductive winter period. We used acoustic monitoring to assess the habitat associations of bats across a managed pine landscape in the southeastern United States. Materials and Methods: During the winters of 2018 and 2019, we deployed acoustic detectors at 72 unique locations to monitor bat activity and characterized vegetation conditions at two scales (microhabitat and landscape). We used linear mixed models to characterize species-specific activity patterns associated with different vegetation conditions. Results: We found little evidence of different activity patterns during winter. The activity of three species (hoary bat: Lasiurus cinereus; southeastern myotis: Myotis austroriparius; and tricolored bat: Perimyotis subflavus) was not related to vegetation variables and only modest relationships were evident for four other species/groups (big brown bat: Eptesicus fuscus; eastern red bat: L. borealis; Seminole bat: L. seminolus; evening bat: Nycticeius humeralis; and Brazilian free-tailed bat: Tadarida brasiliensis). Conclusions: During winter, the bats in our study were active across the landscape in various cover types, suggesting that they do not exhibit the same habitat associations as in summer. Therefore, seasonal differences in distributions and habitat associations of bat populations need to be considered so that effective management strategies can be devised that help conserve bats year round.

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

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.

Mono-specific forest plantations are valuable bat habitats: implications for wind energy development

Near-natural or semi-natural forests such as relatively undisturbed and old deciduous or mixed woodland are considered worth protecting and ecologically valuable habitats for bat conservation. In contrast, mono-specific forest plantations are considered ecologically less valuable; thus, decision-makers recommend these plantations as suitable locations for wind power stations and therefore want to further expand wind turbines in these habitats. This is expected to have a strong negative impact on the landscape because forests would be cleared for wind turbine pads and access roads and wind turbines rise above the trees with adverse impacts for bats. Therefore, we argue that, in light of bat conservation, the suitability of forest plantations for wind energy development is not, per se, warranted and that implications of wind power stations, even in mono-specific forest plantations, should be assessed and evaluated. We conducted long-term bat activity monitoring and recorded bat echolocation calls above the canopies of different forest sites (coniferous monoculture plantations and semi-natural mixed deciduous forests) in Germany and compared different forest types in terms of species richness, total bat activity, activity of the three bat species groups and species composition. Generalised linear models revealed that forest type and the amount of forest biotopes did not enhance bat activity. Ordination showed that species composition was not affected by forest type, location and connectivity. Mono-specific forest plantations can harbour a diverse bat fauna with high species activity and are, therefore, valuable bat habitats just as near-natural or semi-natural woodlands are. Environmental impact assessment and mitigation measures are vital in all forest types before and after planning for wind energy turbines. In particular, future planning and approval processes must consider the importance of mono-specific forest plantations for bat species protection.

The luxury effect beyond cities: bats respond to socioeconomic variation across landscapes

Background

The luxury effect describes the positive relationship between affluence and organism diversity or activity in urban ecosystems. Driven by human activities, the luxury effect can potentially be found at a broader scale across different landscapes. Previously, the luxury effect relationship has been established within a city for two bat species, the red bat (Lasiurus borealis) and the evening bat (Nycticeius humeralis). We examined landscape-scale patterns of bat activity distribution—using empirical data for seven bat species for the luxury effect. We also identified bat-land cover associations for each species. Across North Carolina, USA, we used the mobile transect survey protocol of the North American Monitoring Program to record bat activity at 43 sites from 2015 to 2018. We collected land cover and income data at our transect locations to construct generalized linear mixed models to identify bat-land cover and bat-income relationships.

Results

We found that across landscapes, activity of the red bat and the evening bat was positively correlated to income independent of land cover, consistent with previous single-city results. We found a negative relationship between hoary bat (Lasiurus cinereus) activity and income. All seven species had specific land cover associations. Additionally, we found a positive interaction term between income and evergreen forest for the red bat and a positive interaction term between income and woody wetland for hoary bat.

Conclusions

Our results demonstrated that the luxury effect is an ecological pattern that can be found at a broad spatial scale across different landscapes. We highlight the need for multi-scale ecology studies to identify the mechanism(s) underlying the luxury effect and that the luxury effect could cause inequity in how people receive the ecosystem services provided by bats.

Implementing and Assessing the Efficacy of the North American Bat Monitoring Program

Bats are under threat from habitat loss, energy development, and the disease white-nose syndrome; therefore, an efficient and effective means to monitor bat populations is needed. The North American Bat Monitoring Program (NABat) was initiated in 2015 to provide standardized, large-scale monitoring to benefit bat biologists, managers, and policy makers. Given the recency of this program, our first objective was to determine the efficacy of implementing NABat. Further, because the probability of detecting a bat varies among species and survey conditions, our second objective was to determine factors affecting detection probabilities of bats using NABat acoustic surveys. We conducted surveys across South Carolina from mid-May through July 2015 and 2016. To determine efficacy of NABat, we compared species detections with historical known distributions and predicted distributions based on environmental occupancy models. To determine factors that affected detection probability, we evaluated support for predictive detection models for each species or species grouping. In general, we found that predicted distributions closely matched known distributions. However, we detected some species in ≤50% of cells within their ranges and others outside their ranges, suggesting NABat may also reveal new information about species distributions. Most species had higher detection probabilities at stationary points than mobile transects, but the influence of interrupted surveys, environmental conditions (e.g., temperature, rainfall, and wind) and habitat conditions often varied among species. Overall, our results suggest NABat is an effective and efficient method for monitoring many bat species, but we suggest that future efforts account for species-specific biological and behavioral characteristics influencing detection probability.