Bat Assemblages Research Articles

Response of phyllostomid bat diversity to tree cover types in North-western Ecuador

Agricultural activities affect tropical forest biodiversity; however, some bat species can survive under these anthropogenic changes. We described the characteristics of phyllostomid bat assemblages in tree covers located in 48 plots among four agricultural landscapes of North-western Ecuador. Bats were captured with mist nets installed at a ground level reaching three meters’ height. For each of the plots, we installed a mist net in four types of tree cover (polyspecific live fences, monospecific live fences, cacao plantations, and isolated trees in pastures). We captured 250 phyllostomid bats belonging to 16 species with a trapping effort of 19,200 m2 of net coverage. Polyspecific live fences showed significant differences in relative abundance, richness, and diversity of phyllostomid bats compared to the other three. Frugivorous and nectarivorous guilds were the most abundant, and also exhibited the highest richness among other guilds present in agricultural landscapes. In addition, frugivorous, and nectarivorous guilds increase their abundance and richness in agricultural landscapes, while the animalivorous guild is negatively affected. We recommend installing polyspecific live fences in tropical production systems to support the conservation of phyllostomid bats. We conclude that living fences composed of various plant species favour the abundance, richness, and diversity of phyllostomid bats.

The role of landscape context in shaping bat assemblages in African cacao plantations

Cacao production is mostly concentrated in Africa, with this continent exporting an impressive 68.4 % of the world's cacao. The increasing demand for cacao from the Global North has already led to massive deforestation in Ghana and Ivory Coast and cacao-driven deforestation is likely to continue changing landscapes in Sub-Saharan Africa. Bats are affected by these landscape changes due to their dependence on multiple resources spread at a large spatial scale. Although bats can save cacao farmers millions of euros through pest suppression, no study has investigated how landscape context affects bat communities in African cacao plantations. Here for the first time, we studied how abundance and richness of insectivorous, frugivorous and nectarivorous bats within cacao landscapes could be affected by cover type and the distance between these habitats and each cacao plantation. We sampled bats using mist-nets in 38 cacao plantations spread throughout southern Cameroon from 2017 to 2020. We found that guilds responded differently to the distance and amount of cover of each of the land cover types, with the scale of response being habitat-dependent. Overall, insectivorous bats were associated positively with high cover of natural habitats (e.g., tree cover, rangeland, and flooded vegetation), and negatively with nearby anthropogenic disturbance (e.g., logging and intensive agriculture). Frugivorous and nectarivorous bats were associated to the presence of natural habitats with water and of nearby anthropogenic habitats (e.g., human settlements, community forests and unpaved roads), probably due to the presence of more fruiting and flowering trees. Considering the associations found between the landscape metrics and bats, we propose three different conceptual designs to manage cacao landscapes: one for insectivores, one for frugivores/nectarivores and a third design that maximises the trade-offs between these three guilds. By safeguarding the diversity of these three guilds farmers can maintain pest suppression services within their plantations and guarantee healthy and long-lasting sustainable cacao landscapes through bats' pollination and seed dispersal.

Rabies virus circulation in a highly diverse bat assemblage from a high-risk area for zoonoses outbreaks in the Brazilian Amazon

Bats are the second most diverse order of mammals and play a central role in ecosystem dynamics. They are also important reservoirs of potentially zoonotic microorganisms, of which rabies virus is the most lethal among the bat-transmitted zoonotic pathogens. Importantly, recent outbreaks of human rabies have been reported from the Brazilian Amazon. Here we present a survey of bat species and rabies virus (RABV) circulation in a bat assemblage in the Marajó region, northern Brazil. Using data from mist-net captures and bioacoustic sampling, 56 bat species were recorded along the Jacundá River basin over a 10-day expedition in November 2022. For the investigation of RABV, we used the direct fluorescent antibody test (DFAT) and the rapid fluorescent focus inhibition test (RFFIT). In total, 159 bat individuals from 22 species were investigated for RABV. Five adults of the common vampire bat, Desmodus rotundus, showed RABV-specific antibodies in serum samples. Additionally, we report on local residents with injuries caused by D. rotundus bites and the occurrence of colonies of non-hematophagous bats from different species roosting inside human residences. This scenario raises concerns about the risks of new cases of human rabies and other zoonotic diseases associated with bats in the region and highlights the need for epidemiological surveillance and mitigation measures to prevent outbreaks of emerging infectious diseases.

Functional diversity and trait-environment relationships of bat assemblages in an Amazonian forest-savannah mosaic

Functional diversity and trait-environment relationships of bat assemblages in an Amazonian forest-savannah mosaic

The Quaternary record of fossil bats in the Iberian Peninsula and the Balearic Islands: Palaeobiogeographical changes and palaeoenvironmental implications

Bats are a highly diversified order of mammals found all over the world; however, their population size and distribution are decreasing rapidly in Europe nowadays. The study of ancient bat populations by means of their fossil record is a valuable source of contextual information for modern bat conservation studies. This paper is a comprehensive review of published bat records in the Iberian Peninsula and the Balearic Islands through Quaternary times, representing the first attempt to update and standardize the knowledge of chiropters in southwestern Europe during this time period. The main goal is to identify changes in bat assemblages that might be correlatable to palaeoclimate and palaeoenvironmental changes. Our data show that the Quaternary record of bats in the area is fragmentary and strongly dependent on the presence of karstic cavities. Thus, a strong preservation bias towards colonial cave-dwelling bats exists, and species with alternative ecological requirements are under-represented. Nevertheless, this work reveals that most of the bats inhabiting the area today were already present in the region from at least the Middle Pleistocene. Interestingly, we observe a frequent association between certain cave-dwelling bats (i.e., Rhinolophus ferrumequinum, Miniopterus schreibersii, Myotis myotis and M. blythii) that is still observed in many caves today; this reflects a stable ecology that has remained undisturbed despite past climatic changes. Within the well-documented periods at the end of the Late Pleistocene and the Holocene, a reduction in some common components of Quaternary assemblages (Rhinolophus species and M. schreibersii) is observed, coinciding with the Late Glacial Maximum and the Northgrippian Neoglacial (a cooling event in the Holocene). Finally, the Balearic record shows interesting palaeobiogeographical characteristics, including some eastern taxa absent in the Iberian Peninsula (Rhinolophus variabilis and R. cf. blasii) as well as an unusual abundance of Rhinolophus hipposideros.

Bat species assemblage predicts coronavirus prevalence

Anthropogenic disturbances and the subsequent loss of biodiversity are altering species abundances and communities. Since species vary in their pathogen competence, spatio-temporal changes in host assemblages may lead to changes in disease dynamics. We explore how longitudinal changes in bat species assemblages affect the disease dynamics of coronaviruses (CoVs) in more than 2300 cave-dwelling bats captured over two years from five caves in Ghana. This reveals uneven CoV infection patterns between closely related species, with the alpha-CoV 229E-like and SARS-related beta-CoV 2b emerging as multi-host pathogens. Prevalence and infection likelihood for both phylogenetically distinct CoVs is influenced by the abundance of competent species and naïve subadults. Broadly, bat species vary in CoV competence, and highly competent species are more common in less diverse communities, leading to increased CoV prevalence in less diverse bat assemblages. In line with the One Health framework, our work supports the notion that biodiversity conservation may be the most proactive measure to prevent the spread of pathogens with zoonotic potential.

Scale-dependent influences of environmental, historical, and spatial processes on taxonomic and functional beta diversity of Japanese bat assemblages.

This study investigated the relative influences of environmental, spatial, and historical factors, including the island-specific history of land connectivity, on bat assemblages in the Japanese Archipelago. We collected bat distribution data from 1408 studies and assigned them to Japan's First Standard Grid (approximately 6400 km2). Japanese bat assemblages were analyzed at two scales: the entire Japanese Archipelago comprised 16 islands and exclusively the four main islands. At first, we calculated taxonomic and functional total beta diversity (β total) by Jaccard pairwise dissimilarity and then divided this into turnover (β repl) and richness-difference (β rich) components. We conducted hierarchical clustering of taxonomic beta diversity to examine the influence of the two representative sea straits, Tsugaru and Tokara, which are considered biogeographical borders. Variation partitioning was conducted to evaluate the relative effects of the three factors on the beta diversity. Clustering revealed that the Tokara Strait bordered the two major clades; however, the Tsugaru Strait did not act as a biogeographical border for bats. In the variation partitioning, shared fraction between spatial and historical factors significantly explained taxonomic and functional β total and taxonomic β repl at the entire archipelago scale, but not at the four main islands scale extending only Tsugaru Strait but not Tokara Strait. Pure environmental factors significantly explained functional β total at both scales and taxonomic β total only at the four main islands scale. These results suggest that spatial and historical factors are more pronounced in biogeographical borders, primarily structuring assemblage composition at the entire archipelago scale, especially in taxonomic dimension. However, current environmental factors primarily shape the assemblage composition of Japanese bats at the main island scale. The difference in results between the two scales highlights that the primary processes governing assemblages of both dimensions depend on the quality of the dispersal barriers between terrestrial and aquatic barriers for bats.

Deep biogeographic barriers explain divergent global vertebrate communities

Biogeographic history can lead to variation in biodiversity across regions, but it remains unclear how the degree of biogeographic isolation among communities may lead to differences in biodiversity. Biogeographic analyses generally treat regions as discrete units, but species assemblages differ in how much biogeographic history they share, just as species differ in how much evolutionary history they share. Here, we use a continuous measure of biogeographic distance, phylobetadiversity, to analyze the influence of biogeographic isolation on the taxonomic and functional diversity of global mammal and bird assemblages. On average, biodiversity is better predicted by environment than by isolation, especially for birds. However, mammals in deeply isolated regions are strongly influenced by isolation; mammal assemblages in Australia and Madagascar, for example, are much less diverse than predicted by environment alone and contain unique combinations of functional traits compared to other regions. Neotropical bat assemblages are far more functionally diverse than Paleotropical assemblages, reflecting the different trajectories of bat communities that have developed in isolation over tens of millions of years. Our results elucidate how long-lasting biogeographic barriers can lead to divergent diversity patterns, against the backdrop of environmental determinism that predominantly structures diversity across most of the world.

Importance of riparian vegetation and wood-pastures in the maintenance of bat assemblages in a highly fragmented landscape in Veracruz, Mexico

Abstract To investigate whether trees and palms scattered in pastures contribute to the maintenance of bat assemblages in landscapes highly fragmented by livestock farming activities, we evaluated the bat assemblages and foraging guilds between wooded pastures and riparian vegetation. Using mist nets, we captured 1013 bats from 29 species and four taxonomic families. We found that the abundance, richness, and composition of bat species were not significantly different between vegetation types. Frugivores were the most abundant guild, and their abundance did not differ between vegetation types, indicating that wood-pastures allow the presence of these bats in the landscape. On the other hand, insectivores were more abundant in riparian vegetation and, interestingly, nectarivores were more abundant in pastures, likely due to the great plasticity of species of the genus Glossophaga. Our results are encouraging, since they demonstrate that a rustic pasture management that promoting the presence of scattered trees and palms along with belts of riparian vegetation, allows the maintenance of bat assemblages in a highly fragmented landscape.

Exceptionally Uniform Bat Assemblages across Different Forest Habitats Are Dominated by Single Hyperabundant Generalist Species

Woodland bat assemblages are usually structured in a space according to the distance from the ground, water, and obstacles, features that often define chiropteran hunting tactics. Consequently, the bat species composition differs strongly among various habitats, even within the same forest patch. However, when conducting local bat surveys in Wolin National Park (WPN), we revealed an unexpected uniformity in the qualitative and quantitative structure of bat assemblages, based on mist netting and ultrasound recording. In total, 10 vespertilionid species were detected. Across all methods and sampled habitats, a single species, Pipistrellus pygmaeus, predominated, while no Barbastella barbastellus, an old forest specialist, were detected, despite the abundance of their preferred daily roosts. We also reviewed the literature for mist-netted bat samples in four different habitats in lowland Polish forests. The samples usually clustered based on habitats, and the same habitat classes often clustered very closely despite representing geographically distant forests. The exception was WPN, where all four habitat classes formed a tightly packed cluster. We hypothesize that P. pygmaeus might act as a hyperabundant native species, a successful generalist that reduces the contribution of more specialized taxa in the assemblage. It probably benefits from both forest renaturation and anthropogenic cross-boundary subsidy.

Bats at an Altitude above 2000 m on Pirin Mountain, Bulgaria.

The study describes a pilot survey on bats in the highest areas of Pirin Mountain. The methods included examining subfossil bone remains, mist-netting, and recording echolocation calls. The study was conducted in August 2002 and 2013 and from 2019 to 2020. While in general, bat diversity tends to decrease with increasing altitude due to harsher environmental conditions, the present study, despite a short period, reveals high diversity. Twenty species, more than half of the Bulgarian bat fauna, were detected. The recording and analysis of vocal signatures proved to be the best way to inventory bat diversity. At least 13 species were detected by this method. Vespertilio murinus and Tadarida teniotis together make up more than 60% of all reliably determined echolocation sequences. Significant activity was found for Myotis myotis/blythii, Plecotus auritus, Eptesicus serotinus, and E. nilssonii. The registration of the latter species is of considerable faunistic interest. It was previously only known from a single specimen at one location in the country. The sex and age structure of the bat assemblage suggests that it is likely a swarming assemblage. The area is the highest swarming location in Europe. The results provide valuable information on bat ecology and behaviour, which can be used to inform management and protection efforts.

Changes in diversity and species composition in the assemblage of live and dead bats at wind farms in a highly diverse region.

Besides direct mortality, wind farms also affect aerial fauna by modifying their communities, reducing species diversity and richness through disturbance. During three consecutive years, we used mist nets and acoustic recorders, and conducted carcass searches, to characterize the assemblage of bat species and to estimate bat mortality at two nearby wind farms sited <5 km apart in a highly biodiverse region. We asked whether the diversity, richness and evenness of the assemblages varied yearly, predicting it would decrease through time. Richness and evenness did not change, but the diversity of species recorded acoustically, 96% being aerial insectivores, was significantly lower the third year. We estimate 4 - 15.7 fatalities/MW/year by wind farm, with 63% of species found as carcasses being aerial insectivores. We found >40% of dissimilarity in the species composition of bat assemblages between wind farms despite the short distance between them, with species turnover accounting for more than half of the dissimilarity every year. Similarly, species turnover accounted for >15% of the dissimilarity in the composition of the assemblage of live bats (captured and recorded acoustically) and the assemblage obtained through carcass searches. Our findings suggest that nearby wind farms impact bat communities differentially and aerial insectivores disproportionally. Long term, multi-method surveys are needed to characterize bat communities in highly diverse regions and to evaluate the post-construction effects that wind farms have on them.

Far-reaching displacement effects of artificial light at night in a North American bat community

Artificial light at night (ALAN) is a global pollutant that disrupts circadian rhythmicity and a broad range of physiological processes and behaviors in animals. However, ALAN sensitivity can vary greatly even among closely related species and urgently needs study for much of the world’s nocturnal wildlife, including bats. While an increasing number of bat species have recently been assessed for light tolerance, the spatial extent of ALAN’s influence on bats has received little attention. This information need is a barrier to the protection of bats from ALAN in land-use planning and policy, and the development of best practices that effectively buffer bat habitat from light trespass. To help address this information gap for North America, we experimentally tested the distances up to which ALAN affects presence and activity of light-averse little brown bats (Myotis lucifugus) and big brown bats (Eptesicus fuscus), and the composition of a foraging bat assemblage in Connecticut, USA. We used three residential-scale, white, LED floodlights to expose bat foraging habitat to ALAN and compared acoustic activity of bats at distances of 0, 25, 50, and 75 m from the lights between nights when the lights were on versus off. Little brown bats were present on significantly fewer light than dark nights at every distance. Lighting significantly reduced little brown bat activity overall and at the farthest location from the lights (75 m), where it was only 43% of dark-night activity despite < 1 lx of illuminance. Presence of big brown bats was not significantly affected at any distance. Big brown bat activity on light nights averaged 48–75% of dark-night activity at each distance but was significantly lower only at 0 m. As expected, lighting had no effect on eastern red (Lasiurus borealis) or hoary bat (L. cinereus) presence or activity. Community composition on dark and light nights had an average dissimilarity of 38% and significantly differed at 0 m and 25 m. We conclude the type of ALAN we studied has a disturbance radius of at least 75 m for the little brown bat and up to 25 m for the big brown bat, with a resulting influence on community composition for up to 50 m. Cumulative habitat loss for the imperiled little brown bat caused by ALAN could therefore be substantial. We urge planners and natural resources regulators to consider these footprints when evaluating indirect impacts to bat habitat from current and future sources of ALAN across these species’ ranges.

Variable shifts in bird and bat assemblages as a result of reduced‐impact logging revealed after 10 years

Abstract Selective logging is the most widespread driver of land‐use change in biodiverse and carbon‐rich tropical forests. However, the effects of selective logging on biodiversity are less than those associated with other drivers of forest degradation. A suite of recent research has shown that reduced‐impact logging (RIL) results in few or no changes to biological assemblages. But because this logging technique is relatively new, most studies have only considered short‐term impacts. We address this research gap by quantifying changes in biodiversity assemblage as a result of RIL over the longer term. We comprehensively sampled bird and bat assemblages pre‐logged, 1 year after, and 10 years after RIL in Guyana, using a before‐after control‐impact (BACI) sampling design. We compared bird and bat assemblages in each timeframe, and additionally appraised the impact of time since logging, and the number of trees harvested across the suite of species which we further divided between different feeding guilds, disturbance sensitivity and vertical stratification of forest use. We found that 1 year after logging only minor changes could be detected, but 10 years later richness had slightly declined in some groups, while others had shown complete recovery. Nectivorous and insectivorous birds, and carnivorous bats declined in richness, while carnivorous birds, showed a clear recovery to a state akin to pre‐logging. This indicates that for some niches a subtle, but long‐term relaxation effect may be occurring, whereby extinction debts are realized long after the initial disturbance, while other groups have either recovered or not changed after logging. Assemblage changes were also predicted by vertical stratification of forest use, with avian species using the understorey and mid–upper levels of the forest being most affected. Synthesis and applications: Our study demonstrates how best practice forestry and logging can maintain healthy vertebrate populations over the long term. Forestry concessions that adopt techniques of low‐harvest RIL and are managed for their long‐term timber provision through extension of regeneration times beyond 10 years after harvest, are likely to benefit from the ecosystem services provided by biodiversity, while also making a valuable contribution to the global conservation estate.

Interspecific variation in lower temperature thresholds of an assemblage of wintering bats

Abstract Winter presents environmental and energetic challenges for temperate insectivorous bats as colder temperatures increase metabolic rates while simultaneously reducing resource availability. While bats in northern regions typically hibernate or migrate to circumvent these adverse conditions, there is growing evidence of winter bat activity as weather permits. Bats at lower latitudes may experience shorter, milder winters, increasing opportunities for activity. To better understand the relationship between ambient temperature and winter bat activity, we deployed acoustic detectors in central Louisiana and eastern Texas and examined data at 3 levels of biological organization: overall bat activity, species richness, and species-specific activity. Across 1,576 detector-nights, we recorded 37,435 bat passes. Bats responded positively to warmer temperatures but the temperature threshold for winter activity varied among species, ranging from 7.2 to 15.6 °C. Consequently, observed species richness increased at warmer ambient temperatures. With activity linked to environmental conditions in a species-specific manner, different subsets of the winter bat assemblage may be active from night to night. Additionally, our study adds to a rather limited body of literature of winter bat activity and provides a baseline for future studies as white-nose syndrome and climate change affect North American bat populations.

Guild Vertical Stratification and Drivers of Bat Foraging in a Semi-Arid Tropical Region, Kenya.

Africa faces significant challenges in reconciling economic and social development while preserving its natural resources. Little is known about the diverse bat community on the continent, particularly in drier ecosystems. A better understanding of the bat community will help improve and inform the management of these ecosystems. Our study aimed to provide detailed information on the main drivers of bat richness and activity at three different heights above the ground in a semi-arid region of Kenya. We assessed how bat activity varied with space and height using acoustic sampling and complementary methods. We sampled 48 sites at ground level and two sites on meteorological masts at 20 m and 35 m above the ground. We recorded more than 20 bat species, including one species of concern for conservation. Our models showed that the use of space varies with bat guild, creating trade-offs in the variables that affect their activity. Low-flying bat species are mostly associated with habitat variables, whereas high-flying species are more dependent on weather conditions. Our study highlights the richness of bat assemblages in semi-arid environments and emphasizes the need for management measures to protect bat diversity in the face of habitat degradation caused by climate change, land management, and development projects.

Aerial insectivorous bat responses to 30 years of forest insularization in a dam-created Amazonian archipelagic landscape

Mega dams result in habitat loss and fragmentation in lowland tropical forests, compromising the diversity and ecosystem functioning in remnant habitat islands. We investigated the structure of aerial insectivorous bat assemblages within insular forest patches created by a vast ∼30-year-old hydropower reservoir and adjacent mainland continuous forests in Central Amazonia. Bats were surveyed using passive bat recorders across 34 sites. We assessed bat assemblage responses to landscape insularization and estimated the contribution of assemblage-wide components of β-diversity. Additionally, we assessed the effects of local vegetation, and both patch and landscape variables on bat species diversity. Continuous forest sites in the mainland retained higher species richness and bat activity compared to islands, leading to divergent species composition between forest sites. Larger islands (>100 ha) and continuous forests tended to share a similar assemblage composition manly drive by species richness differences with a minor contribution of species replacements. Moreover, local vegetation structure, island size, and landscape edge area exerted significant effects on species richness, bat activity, and species composition, with small degraded islands and landscapes dominated by forest edges exhibiting pervasive species loss. Our study highlights the detrimental impacts of forest fragmentation induced by large dams on aerial insectivorous bat assemblages. If new dam projects are inevitable, we recommend the creation of extensive protected areas in land-bridge island systems and their adjacent continuous forests. Those protected sites can minimize the negative impacts of small islands, safeguarding forest quality for forest-dependent bats, which ensures the continuity of their ecosystem services.

The efficacy of performing field surveys during the dry and rainy seasons to estimate species richness and composition of local bat assemblages

AbstractHere we assessed the efficacy of performing field surveys during both dry and rainy seasons to estimate species richness and composition of phyllostomid bats in 12 sites of the Brazilian Atlantic Forest. Our goal was to elucidate two opposite scenarios. If bat species compositions differ between the dry and rainy seasons, then field surveys in both seasons will be considered complementary for estimating local bat assemblages. In contrast, if bat species compositions in the dry season are a nested subset of the species present in the rainy season, then field surveys in both seasons will be considered redundant. Our results showed that field surveys performed only during the rainy season exhibited the same efficacy in recording bat species as field surveys considering both dry and rainy seasons combined. Consequently, the rare species sampled in the rainy season contributed to the uniqueness of communities in terms of species composition. Considering that time, funding, and the number of field personnel available for work are important factors when determining the sampling effort in highly biodiverse regions like the tropics, our results can be useful in establishing protocols for research projects with limited resources aiming to create a comprehensive list of species.

Population estimates of bat assemblages from hot caves in Puerto Rico

Knowledge about the number of bats roosting in caves is critical for their long-term conservation. These roosts may function as shelter from weather or predators, information and social centers, or as nurseries. We provide estimates of bat population from 12 hot caves in Puerto Rico, based on infrared reflectance technology. Populations ranged from a few thousands of individuals to several hundred thousand. At nine caves, estimates were performed twice at different periods during the reproductive cycle. Some caves showed notable variations in the size of the population. A database of caves used by bats throughout the island is also provided, as well as information on the species that have been identified at each cave.

Changing with the times: Seasonal environmental gradients unveil dynamic bat assemblages and vulnerability.

Uncovering the temporal and spatial dynamics of biological communities in response to biotic and abiotic drivers is essential to predict the effects of environmental change on biodiversity. Similarly, estimating species vulnerability in the face of such dynamics is crucial for implementing effective conservation actions. We explored how bat diversity changes over the year across an altitudinal gradient and identified the environmental drivers that shape bat communities. By analysing species' marginality within the biophysical niche space, we evaluated bats' vulnerability to foreseeable environmental changes. Our results suggest that altitude, the proportion of forest cover and shrub cover are the main drivers shaping bat communities year-round. Additionally, while some bat species are restricted to a single ecological assemblage (or ecological preferences group), others show greater plasticity throughout the year. Importantly, we found that although bats associated with highland habitats and forests could be particularly vulnerable to environmental changes (in particular Myotis mystacinus), this vulnerability correlates poorly with their national conservation status. We suggest that species' ecological plasticity is critical for the resilience of biological communities exposed to environmental changes and should be considered when planning tailored conservation strategies.