Bat Community Responses to Structural Habitat Complexity Resulting from Management Practices Within Different Land Use Types — A Case Study from North-Eastern Germany

Unexpected bat community changes along an urban-rural gradient in the Berlin-Brandenburg metropolitan area

Urbanization gradients are increasingly used in ecological studies to discover responses of species communities to different intensities of human-induced habitat transformation. Here, we investigated patterns of bat communities against the background of different urbanization levels using a priori defined urbanization categories based on distance classes (5 km intervals) along a linear transect from the urban core of the city of Berlin westwards into the rural outskirts of the state of Brandenburg. Using linear-mixed effects models, we found that "distance class", as a proxy for urbanization level, is a meaningful and suitable predictor of bat species richness and diversity. We observed an unexpectedly sudden increase in bat species richness and diversity and changes in species-specific activity levels relatively close to the urban center at the transition between urban and peri-urban areas. This change suggests a relevant influence of the peri-urban areas as a "buffer zone" for specific bat species not able to adapt to the heavily modified inner core of the metropolitan area. Although we could demonstrate that anthropogenic noise and artificial light have the potential to predict the variability of bat species activity along the urban-rural gradient, the actual influence on observed shifts in the bat community needs further research.

Structurally rich dry grasslands – Potential stepping stones for bats in open farmland

Agricultural intensification has caused decrease and fragmentation of European semi-natural dry grasslands. While a high biodiversity value of dry grasslands is acknowledged for plants and insects, locally and on landscape level, their relevance for mobile species, such as bats, is unknown. Here we investigate the use of dry grassland fragments by bats in an agriculturally intensified region in Germany and evaluate local and landscape factors influencing bat activity and assemblages. Specifically, we predicted that a combination of local dry grassland structural richness and landscape features as well as their interactions affect bat activity and foraging above dry grasslands. We also expected that these features influence compositions of local bat assemblages. We repeatedly sampled at 12 dry grassland plots with acoustic monitoring and assessed activity and foraging of bat species/sonotypes, which we grouped into guilds known for foraging in open land, at vegetation edges and in narrow spaces. We determined structural richness of the dry grassland plots in field and derived landscape features from digital landscape data. A relatively high proportion of bat species/sonotypes used dry grasslands regularly. The edge space foragers responded positively to higher local structural richness. Their dry grassland use increased when surrounding forests and woody features were less available, but they foraged more on dry grasslands closer to water bodies. Narrow space bat activity on dry grasslands decreased with less landscape connectivity. Open and narrow space foragers responded to local structural richness only in landscape context. For all bat guilds we found increased use of structurally richer dry grasslands when there was more open farmland in the surroundings. This was also the case for edge space foragers, when landscapes were more homogeneous. Lastly, with increasing structural richness, bat assemblages were more dominated by edge space foragers. We show the importance of European dry grassland fragments for the highly mobile group of bats under certain local structural and landscape compositional conditions. Our results underline the value of heterogeneous dry grassland fragments as potential stepping stones in intensively used farmland areas and contribute to evidence based decision making in dry grassland management and bat conservation.

Bats adjust echolocation and social call design as a response to urban environments

Behavioral traits play a major role in the successful adaptation of wildlife to urban conditions. We investigated and compared the acoustic behavior of free ranging bats in rural (Havelland, Brandenburg) and urban (Berlin city center) green areas (n = 6 sites) to assess possible effects of urbanization on bat vocalizations using automated real-time recordings from May to October 2020 and 2021. We show that foraging and social call activity of commonly occurring bat species was lower in urban areas compared to rural areas. We present data on rural-urban variation in acoustic parameters of echolocation and Type D social calls (produced during flight) using the example of the common pipistrelle Pipistrellus pipistrellus. Calls from urban sites revealed significantly higher end and peak frequencies compared to rural site calls. In addition, urban social calls present a higher degree of complexity as they structurally differed from rural social calls with regard to assemblage and number of call components. Moreover, urban social calls were emitted in a presumably different context than rural calls: antagonistic social calls in urban areas were detected throughout the year and in the acoustic absence of conspecifics and heterospecifics. Our results provide evidence for the ability of P. pipistrellus to modulate temporal and spectral features of echolocation and social calls, as well as patterns of social call production, in order to compensate for constraints imposed by the urban acoustic environment. We suggest that this acoustic behavioral plasticity plays a major role in the degree of adaptation of insectivorous bats to urban habitats.

Using Forest Compensation Funds to Reverse Biodiversity Loss: A Case Study of Turin–Lyon High-Speed Railway Line

Megaprojects radically change the landscape due to their large-scale and high investments. Forests are often one of the most affected habitats, as they are frequently included in megaproject construction sites. These habitats support rich animal communities that the new settlement may threaten. Among all species present in any construction site, those listed in the Habitats Directive (92/43/CEE) deserve particular attention as they are protected throughout Europe. Here, we present a case study related to the expansion of an industrial site, part of the megaproject Turin–Lyon high-speed railway, where forest compensations were used to reverse biodiversity loss. The site expansion scheduled for 2020 included mature forests and clearings that used to host a butterfly species and at least 15 bat species protected by the Habitats Directive and other taxa of conservation concern. Forest compensations are usually used to finance tree plantations and forest improvements. In this case study, for the first time, we used them to maintain local biodiversity, which otherwise would have been severely compromised by the site expansion. Indeed, our approach has made it possible to allocate forest compensation funding to restore or improve habitats to favor biodiversity. This approach may be exported to other megaprojects to support local biodiversity.

Spatial Behavior and Habitat Use of Two Sympatric Bat Species

Simple Summary

Few studies refer to ecological differences of genetically close and morphologically almost identical insectivorous bat species. However, this information is indispensable for effective and sustainable nature conservation strategies. This study aims at investigating differences in the spatial ecology of the long-eared bat species Plecotus auritus and Plecotus austriacus in a typical cultural landscape of Brandenburg, where the two species occur sympatrically. The reconstruction of the prey spectrum revealed that P. auritus and P. austriacus strongly overlapped in their diet. Our results suggest that resource partitioning is based on using different foraging habitats. While radio-tracked females of P. auritus were strongly associated with woodland patches resulting in small-scale activity areas of only few square kilometers, activity areas of P. austriacus encompassed a large-scale matrix of grassland habitats in the magnitude of a small town. Based on these results, we identify priority conservation needs for the two species to ensure that these differences in the spatial behavior and habitat use can be adequately taken into account for future nature conservation efforts.

Abstract

Movement behavior and habitat use of the long-eared bat species Plecotus auritus and Plecotus austriacus were studied in the Havelland region in Brandenburg (Germany). Data collection included mist-netting, radiotelemetry, reconstruction of prey items, and monitoring of roosting sites. Body measurements confirm a high degree of phenotypic similarity between the two species. Total activity areas (100% Minimum Convex Polygons, MCPS) of Plecotus austriacus (2828.3 ± 1269.43 ha) were up to five-fold larger compared to Plecotus auritus (544.54 ± 295.89 ha). The activity areas of Plecotus austriacus contained up to 11 distinct core areas, and their mean total size (149.7 ± 0.07 ha) was approximately three-fold larger compared to core areas of Plecotus auritus (49.2 ± 25.6 ha). The mean distance between consecutive fixes per night was 12.72 ± 3.7 km for Plecotus austriacus and 4.23 ± 2.8 km for Plecotus auritus. While Plecotus austriacus was located most frequently over pastures (>40%) and meadows (>20%), P. auritus was located mostly within deciduous (>50%) and mixed forests (>30%) in close vicinity to its roosts. Roost site monitoring indicates that the activity of P. austriacus is delayed relative to P. auritus in spring and declined earlier in autumn. These phenological differences are probably related to the species’ respective diets. Levins’ measure of trophic niche breadth suggests that the prey spectrum for P. auritus is more diverse during spring (B = 2.86) and autumn (B = 2.82) compared to P. austriacus (spring: B = 1.7; autumn: B = 2.1). Our results give reason to consider these interspecific ecological variations and species-specific requirements of P. auritus and P. austriacus to develop adapted and improved conservation measures.

Landscape Transformation Influences Responses of Terrestrial Small Mammals to Land Use Intensity in North-Central Namibia

In this study, we investigate and compare the response patterns of small mammal communities to increasing land use intensity in two study areas: private farmland at the southern boundary of Etosha National Park and smallholder farmland in Tsumeb agricultural area. Species richness, community composition and a standardized capture index (RCI) are compared between sites of (a) increasing grazing pressure of ungulates (Etosha) and (b) increasing conversion of bushland to arable land (Tsumeb). Within each study area, we found clear response patterns towards increasing land use intensity. However, patterns differ significantly between the two areas. Within the less-transformed area (Etosha), high land use intensity results in a decrease in the RCI but not species richness. Small mammal communities remain relatively stable, but ecosystem functions (e.g., bioturbation, seed dispersal) are weakened. Within the more-transformed area (Tsumeb), high land use intensity leads to a decrease in species richness and increasing RCIs of two common pest species. The disappearance of a balanced community and the dramatic increase in a few pest species has the potential to threaten human livelihoods (e.g., crop damage, disease vectors). Our comparative approach clearly indicates that Gerbilliscus leucogaster is a possible candidate for an ecological indicator of ecosystem integrity. Mastomys natalensis has the potential to become an important pest species when bushland is transformed into irrigated arable land. Our results support the importance of area-specific conservation and management measures in savanna ecosystems.

Decrease in Bat Diversity Points towards a Potential Threshold Density for Black Cherry Management: A Case Study from Germany

In times of land use changes towards more close-to-nature forestry, the application of bioindicators becomes an interesting tool for effective land-use management schemes. Forest managers are increasingly confronted by alien tree species. Therefore, this case study aimed to investigate the influence of the invasive black cherry (Prunus serotina) on bats (Chiroptera: Verpertilionidae) in pine (Pinus sylvestris) forest ecosystems, in order to identify the potential of bats as bioindicators for a black cherry invasion. In three pre-classified succession stages of the black cherry, the diversity and relative abundance of bats were bioacoustically monitored for a period of 60 nights. From the bat call recordings made during the study period, eight bat species could be identified to species level. Within the succession stages of pine monoculture and light black cherry forest, a comparable bat diversity of eight bat species and three sonotypes with a similar relative abundance were observed. In dense black cherry forest, only four species and one sonotype were detected. Compared to the pine monoculture and light black cherry forest, the overall abundance of the bat community was significantly lower in the dense black cherry forest. Upon evaluation, those bat species associated with the edge and narrow space forager guilds were found to have a high sensitivity to a dense black cherry understory within naturally monocultural pine stands. Their activity patterns indicate that the transition from light to dense black cherry understory can be considered as a potential threshold value for a close-to-nature black cherry understory density in high canopy pine forest stands.