Activity Of Insectivorous Bats Research Articles

More trees and fewer roads: the importance of local and landscape features for insectivorous bats in open urban green spaces

Context Urbanisation poses new challenges for wildlife worldwide, and recent research suggests that urban parks, although highly modified, may act as important refuges. Insectivorous bats can persist in urban landscapes and play an important role in keeping insect populations in balance. Previous research on use of urban landscapes by these bats has often focused on patches of remnant bushland within cities, but their use of highly modified open spaces is not well understood. Aims We aimed to determine the use of open green spaces (e.g. open parks, sports ovals) by insectivorous bats in Melbourne, Australia and to identify landscape factors that influence their presence and activity level. Methods We conducted passive acoustic surveys at 35 sites across greater Melbourne. Once species were identified from the echolocation call data, we modelled species richness, total activity and activity of individual species against landscape and weather variables, using Generalised Linear Mixed Models and Generalised Additive Mixed Models. Key results Across 557 detector nights, we identified at least 11 of the 17 species recorded to occur in Melbourne. Both species richness and activity were greater in areas with more nearby trees and lesser in areas with more roads. There were weaker species-specific relationships between bat activity and both distance to the nearest water source and Normalised Difference Vegetation Index. Species richness and activity levels were lower on nights with a lower temperature at dusk, higher rainfall and stronger wind. Conclusions Our results show that multiple bat species consistently use Melbourne’s open green spaces, highlighting the potential habitat value of these areas, especially those surrounded by high tree densities and fewer roads. Implications Insectivorous bats play important roles within ecosystems and bring benefits to human society. To encourage the diversity and activity of insectivorous bats in urban landscapes, we recommend retaining and increasing indigenous vegetation surrounding open areas in urban parks, as well as more strategic planning of new urban parks that further increases tree density in cities.

Invasion by common reed in peri-urban wetlands does not affect insectivorous bat activity, despite a negative effect on prey abundance

Common reed (Phragmites australis), an exotic invasive plant in North America, alters wetlands and thus affects the abundance, development and behavior of many animal species. We evaluated the effect of common reed invasion on 1) the abundance of nocturnal flying insects, and 2) the activity of one of their predators, insectivorous bats. As bats are highly mobile, they can be affected by parameters at a broad scale. Therefore, we considered 3) the effect of habitats and roads around invaded and non-invaded sites on bat activity. We selected 28 paired sites located in wetlands in southwestern Quebec: 14 control sites and 14 common reed-dominated sites. Nocturnal flying insects were collected in some sites, using light traps. The activity of bats was measured in all sites using acoustic detectors. Habitats and high-traffic roads around the sampled sites were characterized over several spatial scales, using ArcGISPro. Our results showed that the number of nocturnal flying insects was reduced by 53% in common reed-dominated sites, but there was no influence on the overall activity of insectivorous bats. Instead, a larger relative area of aquatic and woodland habitats, within a respective radius of 1 and 2 km in the vicinity of our study sites, favoured the overall activity of bats. Moreover, bat activity decreased with an increase in the length of high-traffic roads within a radius of 200 m around the studied wetland sites. Our results suggest that invasive plants despite reducing insect prey may not represent a major threat to insectivorous bats. They also highlight the importance of protecting forests and aquatic habitats, as well as the need to implement road mitigation measures for the conservation of insectivorous bats.

Providing water sources to insectivorous bats for conservation biological control in arid date plantations

Balance between the high demand for agricultural production and the negative environmental impact of intensive agriculture requires the development of sustainable agricultural approaches. One such approach is conservation biological control (CBC), which aims at enhancing pest suppression by using natural enemies, such as predators and parasites. Insectivorous bats are considered as potential natural enemies for CBC of insect agricultural pests. Bats drink from open water sources and forage above them, hence we hypothesized that supplementation of artificial water pools adjacent to desert date plantations might promote the activity and species richness of insectivorous bats in this habitat, thereby contributing to pest suppression. We predicted that bats will be more attracted to the pools during summer, when other water sources are scarce, than during spring. In addition, we explored the effect of water supplements on the desert bat community structure. Eight pools were installed in a date plantation in the hyper-arid Arava valley, Israel. Bats were acoustically monitored during three experimental stages: 1) before filling the pools with water; 2) while the pools held water and 3) after emptying them. The lesser date moth (Batrachedra amydraula), a major date pest, was monitored using pheromone traps in parallel with the experimental stages. We found that the pools increased bat activity in summer, but not in spring, while species richness was not affected in either season. The local bat community structure was significantly altered while the pools held water, but not due to increased activity of synanthropic Mediterranean species at the expense of local desert species. The number of individuals of the lesser date moth near the pools decreased with the increase in bat activity. Our results support the idea that seasonal water supplementation enhances bat activity in arid farmlands with potential contribution to pest control and the actual contribution to pest suppression should be further quantified. We suggest that the integration of small artificial pools to promote agricultural pest predation by bats may help reduce crop loss and potentially contribute to the conservation of desert bat communities by adding water sources.

Insectivorous bats in Indian rice fields respond to moonlight, temperature, and insect activity

ContextRice, India’s most widely grown crop, suffers substantial and increasing yield loss to insect pests. Insectivorous bats are known suppressors of insect pests, providing significant economic value to agricultural systems worldwide, yet their ecology in Indian agricultural landscapes is poorly understood.ObjectivesWe assess the influence of key biotic and abiotic factors on the activity of insectivorous bats over the growing season and within a night in a rice cultivation landscape.MethodsPassive acoustic recorders were used to track bat activity in a rice field in the Sonitpur district of Assam, India. We used generalised linear mixed models to analyse the effect of temperature, insect activity, and moonlight intensity on the activity of six bat sonotypes. We also used a multimodal analysis to describe the within-night activity patterns of these sonotypes.ResultsMinimum nightly temperature and moonlight intensity had a positive and negative influence, respectively, on the activity of six bat sonotypes, while the activity of four bat sonotypes increased with insect activity. Within-night activity showed one of two patterns: three sonotypes displayed a dusk peak in activity, while the three other sonotypes were active through the night.ConclusionThe potential to maximise natural pest control in agricultural landscapes can only be realised through understanding the ecology of natural enemies in these landscapes. Our findings suggest that bats in rice fields are tracking insects over a season and within a night, pointing to a valuable ecosystem service in Indian agriculture that is yet to be quantified.

Landscape features drive insectivorous bat activity in Indian rice fields

ContextInsectivorous bats have been shown to control a number of agricultural insect pests. As bats exhibit species-specific responses to the surrounding landscape, tied closely to their morphology and foraging mode, the activity and distribution patterns of bats, and consequently the ecosystem services they provide, are influenced by the landscape characteristics.ObjectivesThis study aims to determine which features in the landscape surrounding rice fields influence the activity levels of insectivorous bats, and at what scales they are most influential.MethodsWe collected acoustic recordings to determine activity levels of seven bat sonotypes in rice fields surrounded by a variety of land-cover types in the Nagaon district of Assam, India. Using this, we determined the most important set of features in the surrounding landscape, and the scales at which had the strongest impact, for each sonotype.ResultsOur results suggest that tree cover variables are the most important predictors of bat activity in rice fields. Distance to nearest forest, area of forest within 1 km, distance to nearest forest edge, and landscape heterogeneity influenced all five of the analysed bat sonotypes. Also important were the amount of urban land within 1 km, which exerted a negative effect on the activity of one sonotype, and moonlight activity, which negatively influenced the activity levels of one sonotype.ConclusionOur results demonstrate that when flying over rice fields, bat activity is most influenced by presence and proximity of trees. Therefore, increasing tree cover in agricultural landscapes will increase bat activity and likely the level of pest control.

Biotic and abiotic factors shaping bat activity in Maryland soybean fields

AbstractBats are important pest control agents in agriculture. Yet, the underlying fine‐scale biotic and abiotic mechanisms that drive their foraging behaviors and responses to insect outbreaks are unclear. Herbivore‐induced plant volatiles (HIPVs) can attract both invertebrate and vertebrate natural enemies that use the chemical plant cues to locate insect prey. The ability of HIPVs to attract multiple species raises the question of whether they may also be a biotic factor influencing insectivorous bat activity. Additionally, abiotic factors, such as weather conditions, can affect bat activity in agricultural settings, but little is known about how bats respond to shifting environmental conditions on short timescales in this landscape context. Using a model crop system, soybean (Glycine max), our study asked three questions: (1) Which bat species are active in eastern Maryland soybean fields? (2) Is insectivorous bat activity affected by naturally occurring soybean HIPVs and/or synthetic soybean HIPVs (indole or farnesene)? (3) How is insectivorous bat activity affected by hourly weather conditions in this landscape? In soybean fields in eastern Maryland, we created paired treatment plots: HIPV plots (damaged plants or synthetic HIPV dispensers) and control plots (undamaged plants or empty dispensers). We measured bat activity using ultrasonic recorders, summarizing hourly and nightly activity, and detected 10 total species. The most abundant species were big brown/silver‐haired bats (Eptesicus fuscus/Lasionycteris noctivagans). Bat activity did not significantly differ between control and HIPV plots in any of the three experiments. Thus, our results do not support our expectation that bats in eastern Maryland use soybean HIPVs to locate insect prey. However, bat activity did increase with increasing average hourly temperature and wind speed. This initial study of bats and HIPVs, as well as the fine‐scale examination of weather conditions on bat activity, may serve as a guide for future research on bat–plant interactions that can support the development of new strategies for sustainable pest management.

Foraging guild modulates insectivorous bat responses to habitat loss and insular fragmentation in peninsular Malaysia

Despite mounting evidence on the ecological impacts of damming for biodiversity, little is known regarding its consequences in the hyper-diverse Southeast Asian tropical forests. Here we assess the effects of habitat loss and fragmentation on the diversity and activity of insectivorous bats within the hydroelectric Kenyir Lake in peninsular Malaysia. We surveyed bat assemblages on 26 islands and two mainland continuous forest sites using passive acoustic monitoring. Echolocation calls were classified into sonotypes, each corresponding to either one or multiple species, and grouped into foraging guilds. We then examined bat overall assemblage (sonotype richness, activity, and composition), guild- and sonotype-specific activity. From 9360 h of recordings, we identified 16 bat sonotypes, including 10 forest (2854 bat passes), three edge (13703) and three open-space foragers (3651). Sonotype richness increased towards denser canopy structures, as indicated by higher Normalized Difference Vegetation Index values (NDVI). Sonotype composition varied across the gradient of forest area. Forest foragers were positively affected by NDVI and negatively affected by distance to the closest neighbour, whereas edge foragers' activity increased in smaller islands. Of the six sonotypes analysed, the activity of one forest sonotype increased with forest area, while that of one edge sonotype decreased. Ensuring habitat quality within insular forest remnants, in addition to their functional connectivity, maximises bat diversity, including the persistence of forest foraging species. Future hydropower development should therefore avoid the creation of a myriad of small, isolated, and habitat-degraded islands further characterised by altered levels of bat diversity and guild-level activity.

A light-exploiting insectivorous bat shows no melatonin disruption under lights with different spectra.

Natural light-dark cycles synchronize an animal's internal clock with environmental conditions. The introduction of artificial light into the night-time environment masks natural light cues and has the potential to disrupt this well-established biological rhythm. Nocturnal animal species, such as bats, are adapted to low light conditions and are therefore among the most vulnerable to the impacts of artificial light at night (ALAN). The behaviour and activity of insectivorous bats is disrupted by short-wavelength artificial light at night, while long-wavelength light is less disruptive. However, the physiological consequences of this lighting have not been investigated. Here, we examine the effect of LEDs with different spectra on urinary melatonin in an insectivorous bat. We collected voluntarily voided urine samples from Gould's wattled bats (Chalinolobus gouldii) and measured melatonin-sulfate under ambient night-time conditions (baseline) and under red (λP 630 nm), amber (λP 601 nm), filtered warm white (λP 586 nm) and cool white (λP 457 nm) LEDs. We found no effect of light treatment on melatonin-sulfate irrespective of spectra. Our findings suggest that short-term exposure to LEDs at night do not disrupt circadian physiology in the light-exploiting Gould's wattled bat.

Insect Pest Pheromone Lures May Enhance the Activity of Insectivorous Bats in Mediterranean Vineyards and Apple Orchards

Insectivorous bats may play a significant role in regulating populations of agricultural pests. Currently, few methods are available to enhance the activity of bats in agroecosystems. We asked whether synthetic sex pheromones, used in integrated pest management (IPM) to impede the mating success of major moth pests in vineyards and apple orchards, could also enhance the activity and richness of insectivorous bats, their natural enemies. We hypothesized that applying concentrated sex pheromones of pest moths will alter the movement patterns of male moths, indirectly affecting bat richness and activity. We compared the effect of sex pheromones on bats under two different agricultural management systems: conventional farming and IPM. We used synthetic sex pheromones of Lobesia botrana or Cydia pomonella; both are among the most destructive moth pests in vineyards and apple orchards, respectively. Using passive acoustic monitoring, we compared species richness and bat activity in plots without and with additional pheromones. In both IPM vineyards and IPM apple orchards, total bat activity and species richness significantly increased after applying the pheromone treatment, with a positive correlation between total bat activity and the numbers of moth pests in the vineyards. In conventional vineyards, bat species richness increased significantly, but not total bat activity. IPM vineyards had significantly higher species richness than conventional vineyards, both before and after the pheromone treatment. Our study shows that moth pheromone lures, commonly used as a pest control method, may also attract insectivorous bats, which in turn may further suppress the pests. These findings highlight the potential of insectivorous bats as pest control agents and call for further research directed at integrating them in IPM practices.

How different farming practices influence the activity of insectivorous Neotropical bats

Recent bioacoustic studies have shown different responses of insectivorous bats to native habitat loss. We examined the activity and species/sonotypes composition of aerial insectivorous bats present in a human-modified karst landscape in Southeast Brazil, characterized by the presence of semideciduous forest, pastures and Eucalyptus globulus monocultures. Using ultrasonic detectors, we investigated activity and identified bat species and/or sonotypes in the three habitat types. We compared the activity (as a surrogate for abundance) and composition of species/sonotypes present and used Generalized Linear Models to investigated whether canopy density, understory density and food availability influence the response of bats in these habitat types. Our main results demonstrate that the variables general passes and species/sonotype richness did not differ significantly between forest and pasture, however, both variables in these two environments differed significantly from the values ​​found for eucalyptus. We conclude that, in the studied agropastoral landscape, pastures interspersed with forest areas can be used by aerial insectivorous bats during foraging. However, we also found evidence that eucalyptus monocultures, not yet mature and without an understory, have a negative impact on the species/sonotype richness and activity of Neotropical aerial insectivorous bats.

Insectivorous Bats in Eastern Mediterranean Planted Pine Forests—Effects of Forest Structure on Foraging Activity, Diversity, and Implications for Management Practices

Bats are primarily forest mammals and forest structure may affect their communities through the level of vegetation clutter. Pine plantations are typically even-aged managed forests that lack structural complexity. However, an understory layer can enhance the heterogeneity of these forests, making them suitable for several animal taxa. We hypothesized that species composition, richness, and foraging activity of insectivorous bats in pine plantations vary according to forest structure, specifically with the density of the understory. We measured pine density, Diameter at Breast Height (DBH), canopy closure, and vegetation cover of 29 pine (Pinus halepensis) plantations of the Judean Lowlands, Israel, and collected acoustic data on resident bats. We found that bat species richness and total activity increased in forests with large tree DBH and dense shrubs. Cluttered-habitat species foraged preferentially in forests with large tree DBH and high pine density, while open-habitat species preferred forests with well-developed canopies and dense shrubs. Pipistrellus pipistrellus and Eptesicus serotinus foraged in mature forests with well-developed bushes and these species are endangered in Israel. We conclude that mature planted pine forests with a well-developed under-canopy are suitable foraging grounds for insectivorous bats. Management plans for planted pine forests should consider our findings to support bat populations, including rare and endangered species.

How do we sleep while our beds are burning? Impacts of the 2019–20 mega-fires on a rainforest dependent species – the Golden-tipped Bat Phoniscus papuensis

ABSTRACT The Australian summer of 2019/20 was impacted by megafires of a magnitude and severity never previously recorded. Whilst low severity fire has positive benefits for increased insectivorous bat activity and diversity, little information is available on the impact on rainforest specialised clutter dependant species such as the Golden-tipped Bat Phoniscus papuensis. Our aims were to assess the effects of fire on occupancy of habitat across the geographic range of P. papuensis in NSW, to determine the smaller scale effects of fire on use of diurnal roosts in rainforest through radio tracking and to trial the use of artificial structures to temporarily increase roost availability in burnt habitat. We observed that widespread fire encroaching on rainforest has a negative association with occupancy by P. papuensis, with this metric ~78% lower than in unburnt forest. In burnt areas, P. papuensis preferentially used unburnt refugia for their roosting sites in suspended bird nests and the loss of these habitat structures likely contributes to the disappearance of P. papuensis from the landscape. Artificial roosts were not used in the short-term (< 2 years post fire) and do not appear to be a feasible management tool. With the increasing frequency and extent of wildfires the most important factor for P. papuensis to persist in the landscape into the future is the protection of its habitat through ensuring sensitive management of large tracts of connected rainforest to help buffer against the encroachment of future mega-fires.

Contrasting Effects of Chronic Anthropogenic Disturbance on Activity and Species Richness of Insectivorous Bats in Neotropical Dry Forest

For prioritizing conservation actions, it is vital to understand how ecologically diverse species respond to environmental change caused by human activity. This is particularly necessary considering that chronic human disturbance is a threat to biodiversity worldwide. Depending on how species tolerate and adapt to such disturbance, ecological integrity and ecosystem services will be more or less affected. Bats are a species-rich and functionally diverse group, with important roles in ecosystems, and are therefore recognized as a good model group for assessing the impact of environmental change. Their populations have decreased in several regions, especially in the tropics, and are threatened by increasing human disturbance. Using passive acoustic monitoring, we assessed how the species-rich aerial insectivorous bats—essential for insect suppression services—respond to chronic human disturbance in the Caatinga dry forests of Brazil, an area potentially harboring ca. 100 bat species (nearly 50% are insectivorous), but with > 60% its area composed of anthropogenic ecosystems under chronic pressure. Acoustic data for bat activity was collected at research sites with varying amounts of chronic human disturbance (e.g., livestock grazing and firewood gathering). The intensity of the disturbance is indicated by the global multi-metric CAD index (GMDI). Using Animal Sound Identifier (ASI) software, we identified 18 different bat taxon units. Using Hierarchical Modeling of Species Communities (HMSC), we found trends in the association of the disturbance gradient with species richness and bat activity: species richness was higher at sites with higher human disturbance, whereas bat activity decreased with increasing human disturbance. Additionally, we observed taxon-specific responses to human disturbance. We conclude that the effects of chronic anthropogenic disturbance on the insectivorous bat fauna in the Caatinga are not homogeneous and a species-specific approach is necessary when assessing the responses of local bats to human disturbances in tropical dry forests, and in other biomes under human pressure.

Stretching the Habitat Envelope: Insectivorous Bat Guilds Can Use Rubber Plantations, but Need Understorey Vegetation and Forest Buffers

Effects of land-cover change on insectivorous bat activity can be negative, neutral or positive, depending on foraging strategies of bats. In tropical agroforestry systems with high bat diversity, these effects can be complex to assess. We investigated foraging habitat use by three insectivorous bat guilds in forests and rubber plantations in the southern Western Ghats of India. Specifically, we monitored acoustic activity of bats in relation to (1) land-cover types and vegetation structure, and (2) plantation management practices. We hypothesized that activity of open-space aerial (OSA) and edge-space aerial (ESA) bat guilds would not differ; but narrow-space, flutter-detecting (NSFD) bat guild activity would be higher, in structurally heterogeneous forest habitats than monoculture rubber plantations. We found that bat activity of all guilds was highest in areas with high forest cover and lowest in rubber plantations. Higher bat activity was associated with understorey vegetation in forests and plantations, which was expected for NSFD bats, but was a surprise finding for OSA and ESA bats. Within land-cover types, open areas and edge-habitats had higher OSA and ESA activity respectively, while NSFD bats completely avoided open habitats. In terms of management practices, intensively managed rubber plantations with regular removal of understorey vegetation had the lowest bat activity for all guilds. Intensive management can undermine potential ecosystem services of insectivorous bats (e.g., insect pest-control in rubber plantations and surrounding agro-ecosystems), and magnify threats to bats from human disturbances. Low-intensity management and maintenance of forest buffers around plantations can enable persistence of insectivorous bats in tropical forest-plantation landscapes.

Bat activity response to fire regime depends on species, vegetation conditions, and behavior

Disturbances such as fire play an important role in shaping forests and the wildlife they support. As such, forest managers employ prescribed fire to restore ecosystem function, promote forest biodiversity, and maintain wildlife habitat. To better understand how bats respond to variation in fire regime, we used acoustic recorders to quantify bat activity in forests maintained by frequent fire in southern Florida, USA and modelled this variation as a function of both fire regime and vegetation characteristics. Next, to better understand the mechanisms underlying these responses, we quantified variation in bat foraging efficiency and activity during the important early evening period. We found that even in regions historically maintained by frequent fire, bat activity was more closely associated with vegetation conditions, such as canopy cover and woody understory volume, than fire regime. When vegetation and fire frequency were considered together, the bat activity response was nuanced. Activity across the bat community was greater in forests that had burned more frequently in the previous two decades, but bats appeared more likely to encounter prey in forests that burned less frequently. Species-specific responses added additional complexity, potentially related to size and wing morphology, with larger bats responding more strongly to fire, whereas activity of smaller bats was primarily related to vegetation characteristics. Similarly, activity during the early-evening shifted as a function of fire frequency, but in different directions for different species. Our results suggest that investigations of occurrence or overall bat activity may provide an incomplete understanding of the complex responses to fire regimes that become more apparent when activity is partitioned into more refined metrics. These nuances have implications for management of fire-maintained forests. Though frequent burning may best promote the ecosystem services associated with insectivorous bat activity, a more heterogenous approach to fire management that considers bat species diversity, bat behavior, and vegetation conditions may provide additional benefits to bats.

Habitat disturbance trumps moonlight effects on the activity of tropical insectivorous bats

AbstractChanges in moonlight intensity can affect predation risk and induce changes in habitat use and activity of nocturnal species. However, the effect of moonlight on animal activity is rarely evaluated in human‐modified landscapes and can be of vital importance to understand possible changes in ecosystem services provided by light‐sensitive taxa, such as insectivorous bats. Fragmentation changes forest structure and affects light penetration across the landscape. In this case, the effects of fragmentation on bat activity can be modulated by cyclical variations of moonlight intensity. We acoustically quantified the activity of nine aerial insectivorous bat species in relation to moonlight at the Biological Dynamics of Forest Fragments Project, Central Amazonia. We aimed to understand species‐level variation in activity across habitats (continuous forest, fragments and secondary forest) at different temporal scales: lunar cycle, dark vs. bright nights and within nights. Amazonian aerial insectivorous bats responded more to habitat type than to moonlight, with two and six species showing reduced activity in fragments and secondary forest, respectively, compared to continuous forest. The lower activity in secondary forest suggests that despite c. 30 years of secondary forest regeneration, it is still less attractive as foraging habitat. An interactive effect of habitat type and moonlight on bat activity was most evident when contrasting dark and bright nights. Our results indicate that fragments have reduced bat activity on extremely bright nights, probably due to higher predation risk in small fragments. Species that emit constant‐frequency calls (Pteronotus spp.) were the ones that most modulated their responses to habitat disturbance and moonlight. Otherwise, moonlight had little effect on hourly activity levels, irrespective of habitat type. Moonlight is capable of modulating the responses of some bat species in disturbed habitats, particularly in fragments.

Temporal and spatial activity of insectivorous bats in arid riparian woodland

Insectivorous bats make a significant contribution to mammalian diversity in central Australia, with 12 known extant species; however, little is known about their habitat preferences and how these interact with temporal patterns in their abundance and activity. Although most species forage widely and in a variety of habitats, we expected that woodlands associated with ephemeral rivers would constitute high-value habitat for bats because they provide tree hollows, suitable structural habitat for foraging, and canopies rich in invertebrate biomass. The aim of this research was to establish whether riparian woodlands were a focus of bat activity and to identify patterns in habitat use and whether these changed through time. We investigated the activity of bats in riparian woodlands and neighbouring vegetation over 2 years. Bat activity was higher in riparian woodland than in nearby vegetation, and this difference was most significant during a hot and dry summer. At the species level, body size and foraging guild were important factors explaining differences in activity, with larger ‘open space’ species more active in riparian woodland than adjacent habitat. In contrast, we did not detect significant differences in the activity of smaller vespertilionid species between habitats. Coinciding with patterns in invertebrate activity, bat activity was highest in summer and lowest in winter. Within river channels, canopy cover was important in explaining patterns in bat activity. There was also a significant location effect, with bat activity in some river systems much higher than in others. We propose that this is related to both regional variability in rainfall and productivity, in addition to topography. Our findings demonstrate the importance of riparian woodlands to bats in an arid environment, particularly during low-resource periods, and suggest that bats may be affected by future climate changes and degradation from fire impacts.

The Limpopo River Exerts a Powerful but Spatially Limited Effect on Bat Communities in a Semi-Arid Region of South Africa

Although the Limpopo River is not perennial in its upper stretches in South Africa, the presence of a narrow riparian forest zone is expected to enhance bat diversity by promoting a wider range of foraging types, but the scale at which this effect may operate is not known. A recent, fine-scale model of bat diversity in Africa suggested that rivers may enhance species richness of bats, but that strong gradients in richness would occur next to rivers especially in savanna areas. We tested this idea by conducting acoustic surveys with bat detectors around six water bodies at distances from 0–12 km from the Limpopo River in two adjacent protected areas, the Mapungubwe National Park and the Venetia Limpopo Nature Reserve. We used a paired design, with each water body having detectors placed at and just away (500–750 m) from it. We found enhanced species richness, diversity and activity at MNP sites closer to the Limpopo (0–5 km) compared with VNR sites located 9–12 km from the Limpopo. Moreover, at VNR but not MNP, the bat community was dominated (32% of calls) by an arid-adapted generalist species, the Cape serotine (Neoromica capensis). Consistent with the proximity of structurally complex riparian vegetation, slow flying, clutter-feeding horseshoe bats (Rhinolophus spp.) were relatively more abundant (12% of calls) at MNP compared with VNR (0.7% of calls). This effect was highly accentuated when correcting for detectability of different species to bat detectors. Proximity to small, natural and artificial water bodies significantly enhanced both species richness and activity, but this effect was much more pronounced at sites > 5 km from the Limpopo compared with sites < 2 km from the Limpopo. We conclude that while major rivers with riparian zones can exert a significant impact on species richness, diversity, activity and community structure of insectivorous bats, this effect may only extend a few kilometres from the river. Protection of riparian zones along rivers in savannas is therefore critical to conserving intact and diverse bat communities.

Species-specific effects of moonlight on insectivorous bat activity in central Chile

Abstract Moonlight intensity influences the activity patterns of bats. Some bat species reduce their activity levels during brighter nights, a phenomenon known as “lunar phobia.” While lunar phobia of bats has been extensively studied in tropical regions, the same is not the case of bats in temperate regions. By using acoustic detectors, we examined differences in the activity of insectivorous bats on nights with different moonlight intensity in an agricultural landscape of central Chile. We also examined the hourly activity patterns throughout the night and how these varied between full and new moon nights. All bat species modified their activity based on the moonlight intensity; however, their effects were species-specific. The activity of Lasiurus varius, L. villosissimus, Myotis chiloensis, and Histiotus montanus was lower during bright nights, while Tadarida brasiliensis was the only species whose activity was higher during bright nights. Hourly activity throughout the night differed between full moon nights and new moon nights in most bat species. During full moon, bats concentrated their activities in the early hours of the nights; a more homogeneous activity pattern was exhibited during new moon night. Our study demonstrates that moonlight affects the activity of bats in Chile, a factor that should be considered when studying bats.

No room to move: bat response to rainforest expansion into long-unburnt eucalypt forest

The expansion of rainforest trees into long-unburnt open forests is widespread globally, including in high-rainfall regions of eastern Australia. Increased tree density can reduce insectivorous bat activity and species richness by constraining echolocation and foraging success. Yet it is unknown whether sclerophyll and rainforest trees differ in their effects on open forest bat communities. We sampled insectivorous bats and nocturnal flying insects at two heights (understorey, canopy) in dry sclerophyll forest of eastern Australia with contrasting fire histories and levels of rainforest pioneer invasion. We found that both time since fire and functional identity of midstorey trees influenced the local bat community, whereas insect biomass had little effect. Long-unburnt forests with a rainforest pioneer midstorey had lower bat activity (63% lower) and species richness (35% lower) than recently burnt forests with a more open midstorey. Bat species richness also declined beneath the dense sclerophyll midstorey in long-unburnt forests, although was unaffected in the canopy above. Strong negative correlations between rainforest tree density and bat community activity and richness indicate that rainforest trees, in contrast with sclerophyll trees, exert additional negative control over open forest bat communities. Our results show that habitat suitability for clutter-intolerant bats declined well before the often-recommended maximum fire-intervals for dry open forest, providing evidence of an upper threshold for fauna conservation in rainforest-invaded open forests. To conserve bat communities in dry open forests vulnerable to rainforest invasion, fire should occur with sufficient frequency to prevent rainforest pioneers developing a dense midstorey that displaces clutter-intolerant bats.