Bat Guilds Research Articles

Community structure of a Neotropical bat fauna as revealed by stable isotope analysis: Not all species fit neatly into predicted guilds

AbstractNeotropical bat communities are among the most diverse mammal communities in the world, and a better understanding of these assemblages may permit inferences about how so many species coexist. While broad trophic guilds (e.g., frugivore, insectivore) of bats are recognized, details of diet and similarities among species remain largely unknown. We used stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) to characterize the community structure of a diverse Neotropical bat fauna from Belize to test predictions of niche theory and the competitive exclusion principle. We predicted that (1) interspecific variation in isotopic overlap would be greater within guilds than between guilds, and (2) no two sympatric populations would have isotopic niches that overlap completely, unless there is variation along some other axis (e.g., temporal, spatial). We additionally tested body size as an explanatory metric of potential overlap and predicted that larger‐bodied animals would have greater niche breadths. Results suggest that while guild‐level characterizations of communities are at least somewhat informative, there are multiple examples of intra‐ and inter‐guild species pairs with significantly overlapping isotopic niches, suggesting that, counter to predictions, they may compete for resources. Understanding the trophic structure of animal communities is fundamental to conservation and management of endangered species and ecosystems and important for evolutionary studies, and stable isotope analyses can provide key insights as well as informing hypotheses of the diet of species that are not well known.Abstract in Spanish is available with online material.

Local-Scale Bat Guild Activity Differs with Rice Growth Stage at Ground Level in the Philippines

High-flying insectivorous bats, as wide-ranging generalist insectivores, are valuable consumers of high-altitude migrating pests of rice in Southeast Asia. Here, we documented the behavior of relatively low-flying bats over irrigated rice to elucidate their potential role as predators of rice-associated pest insects in the Philippines. Specifically, we tested the local-scale effects of rice stage, particularly seedling and late vegetative stages, and time of night on acoustic activity of bats foraging near ground level within three functional guilds (based on foraging distance from background clutter). We also monitored bat activity from two 50 m-high towers to assess the vertical extent of relatively low-flying guilds, as well as document high-flying bat guild presence and temporal behavior. At ground level, the most active guild biased their activity and feeding over early growth stage fields, but also foraged at tower level. Activity of the bat guild adept at foraging closest to vegetation did not vary with time of night or rice stage and was absent from tower recordings. High-flying bats were predictably rare at rice level, but exhibited high foraging intensity at 50 m. Given the well-documented, sequential arrival of insect guilds with growth stage, these data suggest that at ground level edge-space bats may be important consumers of detritivores (e.g., mosquitoes). Moreover, our data suggest that just as habitat heterogeneity enhances the services of arthropod predators, these management practices also enhance bat activity and, presumably, their contribution to pest suppression.

The role of bats in pollination networks is influenced by landscape structure

Nectarivorous bats are essential to the functioning to both agricultural and natural ecosystems in the tropics, yet these pollinator communities are declining as a result of habitat loss and hunting. Temporal variation and habitat changes lead to both roost and floral resource loss, which is the major driver of bat pollination decline. This study aims to determine how the bat pollination networks in mixed-fruit orchards are affected by flowering seasons and different land-use types. We estimated the abundance of nectarivorous and frugivorous bats using video observations to determine floral visitation rates from 18 mixed-fruit orchards in Southern Thailand. Pollination networks were then created based on network level indices (number of interactions and specialisation) and species level indices (strength−dependence of plant on each bat, and generalised degree−the number of interactions per species divided by the number of possible interacting partners) for each bat group at each orchard. We found that specialisation in low season networks was higher than those from peak season. Nectarivorous bats showed higher levels of normalised degree, and strength than frugivorous bats. The normalised degree of frugivorous bats, but not nectarivorous bats increased with the proportion of urban area within 30 km radius. The strength of bats was positively correlated with the proportion of plantations within a 2 km radius. Our results show that both bat guilds are strongly integrated into pollination networks where they occur and provide evidence that increasing the area of plantation and urban alters the degree of generalization of pollinators which can significantly impact pollination success of plants.

Different bat guilds have distinct functional responses to elevation

Understanding biodiversity's responses to environmental variations is a challenging task in ecological research. Under a functional perspective, studies have shown that environmental alterations can affect organisms' traits that are related to their performance, fitness and ecological functions. In the present study, we evaluated how the diversity and functional traits of two distinct bat guilds are affected by an elevational gradient in Atlantic forest, southeastern Brazil. Indices regarded to functional diversity and to dominant functional traits (Rao Quadratic Entropy - RaoQ and Community Weighted Mean - CWM) were calculated for both bat guilds: understory and open-space bat faunas. Generalized Linear Models (GLMs) were applied to verify the relation of each metric with elevation, and the presence of non-linear relationships were tested. Results showed that each guild of the bat community reacted differently to the elevational gradient, with statistically significant results of RaoQ for understory bats and of CWM for both guilds (for aspect ratio) or for only one bat guild (mass for understory bats and wing load for open-space bats). Our results illustrate how an environmental gradient can impose different selective pressures in each bat guild and how the distinct bat groups are affected by elevation. This is the first study considering functional aspects of open-space bats in the Neotropics.

Road effects on bat activity depend on surrounding habitat type

The effects of roads on bats are still a poorly documented issue. Most of the available research focuses on large and high-traffic highways, while low-medium-traffic roads are often assumed to have negligible impacts. However, small roads are ubiquitous in landscapes around the world. We examined the effects of these roads, as well as habitat types, on the activity of three bat guilds (short-, mid- and long-range echolocators) and the most common bat species Pipistrellus kuhlii. We performed three bat acoustic surveys between May and October 2015, with these surveys being performed along twenty transects that were each 1000 m long and perpendicular to three roads with different traffic volumes. The surveys were performed in dense Mediterranean woodland (“montado”) and open agricultural field habitats, which were the two dominant land uses. At each transect, bat activity was simultaneously registered at 0, 50, 100, 200, 500 and 1000 m from the road with the use of an ultrasound recorder. According to the generalized linear mixed effects models, the overall activity of bats and of the short- and mid-range echolocators increased with increased distance from the roads and was dependent on the surrounding habitats. In contrast, the long-range echolocators and P. kuhlii were more tolerant to road. Our results also show that the activity was higher in woodland areas, however road verges seem to be a significant habitat in an open agricultural landscape. The major negative effects extended to approximately 300 m from the roads in woodlands and penetrate further into the open field (>500 m). The management of roadside vegetation, combined with the bat habitat improvement in areas that are further from the roads, may mitigate the negative effects. To make road-dominated landscapes safer for bats, the transport agencies need to balance the trade-offs between habitat management and road kill risk.

Effect of fire on insectivorous bat activity in northern Australia: does fire intensity matter on a local scale?

Fire is notably becoming more intense, frequent and widespread due to climate change. In northern Australia, inappropriate fire regimes have been implicated in mammal declines, yet nothing is known about how different aspects of fire regimes affect bats in this region. This study aimed to determine how fire intensity, associated with seasonality, affects insectivorous bats on a local scale. An experimental M BACI approach was used on five site replicates across Cape York Peninsula, where ultrasonic detectors were used to determine the activity of insectivorous bats in response to low intensity burns (LIBs) and high intensity burns (HIBs) on a local scale. Total bat activity increased due to LIBs, but showed no response to HIBs. Activity of edge-open guild bats also increased due to LIBs but decreased in response to HIBs. Activity of open guild bats was unaffected by LIBs, but exhibited a strong positive response to HIBs. Activity of closed guild bats showed no response to fire, or fire intensity. Responses were likely derived from changes in habitat structure and prey availability. Given that each bat guild responded differently to each fire intensity, this lends support to the ‘pyrodiversity begets biodiversity’ concept, which is currently the basis for many fire management practices for conservation in northern Australia.

Bat communities respond positively to large‐scale thinning of forest regrowth

Summary Over half of the world's forests are secondary regrowth and support considerable biodiversity. Thinning of these forests is a widespread management practice that can affect forest species, including echolocating bats and their prey. We compared total activity of 11 bat taxa, foraging activity of six bat guilds and biomass of 11 insect orders across four forest thinning categories in managed remnant eucalypt forests in south‐eastern Australia: unthinned regrowth, forest thinned recently (0–4 years) and in the medium term (5–10 years) and reference (mature open forest). Thinning had been carried out at large (˜350 ha) spatial scales. Total bat activity was 60% less and foraging activity was 80% less in unthinned regrowth, compared to reference sites, but activity levels were similar among thinned and reference sites. Insect biomass was greatest in unthinned sites, and while bat activity was related to prey biomass, this relationship was weak in unthinned sites. Together, this suggests that forest structure was more important than prey availability or time since thinning in influencing bat activity patterns. Synthesizing our findings with the broader literature on bats and thinning, we found support for a clutter threshold of 1100 stems ha−1, above which bat activity was markedly lower, across two continents (the USA and Australia) and four broad vegetation types (eucalypt, conifer, deciduous and mixed forests). While elsewhere bats with adaptive traits for open habitats generally respond positively to thinning, in our study, species with traits consistent with clutter tolerance (high call frequency and low wing aspect ratio) had lowest activity levels (up to 22 times) in unthinned regrowth compared to all other forest types. Synthesis and applications. Widespread dense regrowth forest can restrict movement and foraging of bats, even those adapted to clutter. We recommend thinning dense regrowth or plantations to below 1100 stems ha−1 when targeting bat foraging habitat, but effects of thinning on roost habitat and other forest biota require further investigation.

New perspectives on trophic guilds of arthropodivorous bats in North and Central America

AbstractTrophic guilds are useful concepts for advancing our knowledge of trophic structure of communities, dynamics of species interactions, redundancy in ecosystem services, resilience to disturbances, response to climate change, conservation strategies, etc. For insectivorous bats, current literature suggests 8 trophic-related guilds. These include 3 guilds based on the openness of foraging areas, 3 based on the style of feeding, and 2 recently proposed subguilds among gleaners. Some gleaners are “passive,” using densely cluttered vegetation in which echolocation is ineffective, and others are “actively” gleaning, using echolocation to procure prey. None of these guilds is based on the actual diets of bats. We analyzed 33 reports of diet composition representing 51 species of arthropod-feeding bats inhabiting North and Central America. We wanted to determine if the classical guild structure was concordant with the actual diets of bats and to compare guild structure in the Nearctic with that in the Neotropics. Discriminant function and principle component analyses generated 5 groups of genera based on the proportion of various arthropod taxa (mainly orders) in their diets. These groups were very different from classical guilds and showed almost no overlap among bat genera between the 2 continental regions. A similar analysis based on prey flying ability and hardness of their exoskeletons suggested 4 guilds that were more consistent with classical guild concepts, had higher rates of unambiguous guild assignment, and also showed major continental differences. Our results suggest a new arrangement of 4 guilds for arthropod-feeding bats in North and Central America that are based primarily on 2 features of their prey. New molecular techniques should allow us to build on this arrangement by significantly improving the taxonomic level of prey identification.Los gremios tróficos son conceptos útiles para la mejora de nuestros conocimientos sobre la estructura trófica de las comunidades, la dinámica de las interacciones entre especies, la redundancia en los servicios de los ecosistemas, la capacidad de resistencia a las perturbaciones, la respuesta al cambio climático, las estrategias de conservación, etc. Para los murciélagos insectívoros la literatura actual sugiere ocho gremios tróficos. Estos incluyen tres gremios basados en la apertura de las zonas de alimentación, tres con base en el estilo de alimentación, es decir, la búsqueda aérea, caza de arrastre sobre superficies de agua, y recolección de presas en superficies, además de dos sub-gremios propuestos recientemente para los de hábitos recolectores. Algunos gremios son “pasivos”, los cuales forrajean en espacios excesivamente saturados de elementos de vegetación y hacen un uso de ecolocación es ineficaz, y otros recolectores “activos” los cuales utilizan la ecolocación para adquirir presas. Ninguno de estos gremios se basa en las dietas reales de murciélagos. Se analizaron 33 artículos sobre composición de la dieta, los cuales representan 51 especies de murciélagos de alimentación de artrópodos que habitan en Norte y Centro América. El objetivo del presente trabajo fue determinar si la estructura de los gremios clásicos era concordante con las dietas reales de los murciélagos, y comparar la estructura de los gremios entre las regiones Neártica y Neotrópical. En análisis de función discriminante y componentes principales se generaron 5 grupos de géneros con base a la proporción de los diferentes taxones de artrópodos (principalmente órdenes) contenidos en sus dietas. Estos grupos fueron muy diferentes de los gremios clásicos y mostraron casi ningún solapamiento entre los géneros de murciélagos de las dos regiones continentales. Un análisis similar con base en la capacidad de vuelo y la dureza de los exoesqueletos de las presas, ha apuntado a la conformación de cuatro gremios que estaban más en consonancia con los conceptos clásicos de gremio, tuvieron tasas más altas de la asignación inequívoca, y también mostró grandes diferencias continentales. Nuestros resultados sugieren un nuevo arreglo de cuatro gremios de murciélagos de alimentación de artrópodos en Norte y Centro América que se basan principalmente en dos características de su presa. Las nuevas técnicas moleculares deben permitir que construyamos sobre este acomodo, mejorando significativamente el nivel taxonómico de identificación presa.

Later is Better: Optimal Timing for Walked Activity Surveys for a European Bat Guild

Bat activity surveys (walked surveys combining transect and point counts) are extremely important for collecting data throughout Europe in conservation and planning contexts. To ensure optimal data, it is vital to ensure synchronicity between survey time and peak bat activity. However, although protocols for two‐hour dusk activity surveys are well accepted, recommended start time in relation to sunset is a ‘best guess’ rather than based on empirical evidence. Accepted practice differs widely with recommended start times varying from 30 min pre‐sunset (finishing 90 min post‐sunset) to 30 min post‐sunset (finishing 2.5 h after sunset). We provide the first empirical test of optimal start times for dusk activity surveys by comparing bat activity at the same sites on the same nights. Four sites were surveyed, viz. two high‐quality woodland sites and two low‐quality agricultural sites. At each site, surveyors walked the same route and stopped at the same pre‐defined listening points for three repeat surveys per night: 1) starting 30 min pre‐sunset; 2) starting at sunset; and 3) starting 30 min post‐sunset. In total, 240 hours' of data were collected. Four species, all widespread and common throughout Europe, were recorded: common pipistrelle Pipistrellus pipistrellus, soprano pipistrelle P. pygmaeus, Natterer's Myotis natterai and noctule Nyctalus noctule. Recorded bat activity was highest on sunset and post‐sunset surveys both generally (overall bat activity) and for all specific species encountered. Findings were generally consistent for both low‐ and high‐quality habitats. The same species were generally represented in both point and transect data but point data yielded higher estimates of overall activity in low‐quality habitat and higher bat species richness in both high‐ and low‐quality habitat relative to transect data. We recommend that: 1) two‐hour dusk bat activity surveys start at/after sunset not before sunset and 2) both transect and point data are collected and analysed.

Different bat guilds perceive their habitat in different ways: a multiscale landscape approach for variable selection in species distribution modelling

Context Unveiling the scale at which organisms respond to habitat features is crucial to understand how they are influenced by anthropogenic environmental changes. We implemented species distribution models (SDMs) based on multiple-scale landscape pattern analysis for four bat species representative of different foraging guilds: Nyctalus leisleri, Rhinolophus hipposideros, Myotis emarginatus and Pipistrellus pipistrellus. Objectives (a) to assess the environmental factors and the influence of scale on the habitat suitability of bats; (b) to develop an objective methodology to select the best performing variables from a large variable dataset. Methods We performed the study in central Italy (Tuscany): 381 variables were derived from topographical and habitat maps using a moving windows analysis set at three spatial scales (1, 5 and 10 km) that are ecologically meaningful for bats. For each species, weran381univariatemodelstoselectthevariables for multivariate SDMs. Results All the variables retained in the SDMs described spatial pattern indices underlining the importance of landscape structure for species distribution. Species reacted differently in terms of both scale and landscape pattern. P. pipistrellus only responded to variables at 10 km; N. leisleri and M.

Bats are Not Birds – Different Responses to Human Land‐use on a Tropical Mountain

AbstractLand‐use intensification has consequences for biodiversity and ecosystem functioning, with various taxonomic groups differing widely in their sensitivity. As land‐use intensification alters habitat structure and resource availability, both factors may contribute to explaining differences in animal species diversity. Within the local animal assemblages the flying vertebrates, bats and birds, provide important and partly complementary ecosystem functions. We tested how bats and birds respond to land‐use intensification and compared abundance, species richness, and community composition across a land‐use gradient including forest, traditional agroforests (home garden), coffee plantations and grasslands on Mount Kilimanjaro, Tanzania. Furthermore, we asked how sensitive different habitat and feeding guilds of bats and birds react to land‐use intensification and the associated alterations in vegetation structure and food resource availability. In contrast to our expectations, land‐use intensification had no negative effect on species richness and abundance of all birds and bats. However, some habitat and feeding guilds, in particular forest specialist and frugivorous birds, were highly sensitive to land‐use intensification. Although the habitat guilds of both, birds and bats, depended on a certain degree of vegetation structure, total bat and bird abundance was mediated primarily by the availability of the respective food resources. Even though the highly structured southern slopes of Mount Kilimanjaro are able to maintain diverse bat and bird assemblages, the sensitivity of avian forest specialists against land‐use intensification and the dependence of the bat and bird habitat guilds on a certain vegetation structure demonstrate that conservation plans should place special emphasis on these guilds.

Behavioral responses to echolocation calls from sympatric heterospecific bats: implications for interspecific competition

Mutual recognition is the product of species coexistence, and has direct effects on survival and reproduction of animals. Bats are able to discriminate between sympatric different heterospecifics based on their echolocation calls, which has been shown both in free-flying and captive bats. To date, however, the factors that may determine the behavioral responses of bats to echolocation calls from sympatric heterospecifics have rarely been tested, especially under well-controlled conditions in captive bats. Hence, we aimed at tackling this question by performing playback experiments (habituation–dishabituation) with three horseshoe bat species within the constant-frequency bat guild, which included big-eared horseshoe bats (Rhinolophus macrotis), Blyth’s horseshoe bats (Rhinolophus lepidus), and Chinese horseshoe bats (Rhinolophus sinicus). We studied the behavioral responses of these three species to echolocation calls of conspecifics, to other two species, and to another heterospecifics bat, Stoliczka’s trident bat (Asellisus stoliczkanus), which also belongs to this guild. We found that the three rhinolophid species displayed a series of distinct behaviors to heterospecific echolocation but few to conspecific calls after habituation, suggesting that they may have been able to discriminate sympatric heterospecific echolocation calls from those of conspecifics. Interestingly, the behavioral responses to heterospecific calls were positively correlated with the interspecific overlap index in trophic niche, whereas call design had only a minor effect. This implies that the behavioral responses of these bats to heterospecific echolocation calls may be related to the degree of interspecific food competition.

Landscape connectivity, habitat structure and activity of bat guilds in farmland‐dominated matrices

Summary Agricultural intensification has caused a decline in structural elements in European farmland, where natural habitats are increasingly fragmented. The loss of habitat structures has a detrimental effect on biodiversity and affects bat species that depend on vegetation structures for foraging and commuting. We investigated the impact of connectivity and configuration of structural landscape elements on flight activity, species richness and diversity of insectivorous bats and distinguished three bat guilds according to species‐specific bioacoustic characteristics. We tested whether bats with shorter‐range echolocation were more sensitive to habitat fragmentation than bats with longer‐range echolocation. We expected to find different connectivity thresholds for the three guilds and hypothesized that bats prefer linear over patchy landscape elements. Bat activity was quantified using repeated acoustic monitoring in 225 locations at 15 study plots distributed across the Swiss Central Plateau, where connectivity and the shape of landscape elements were determined by spatial analysis (GIS). Spectrograms of bat calls were assigned to species with the software batit by means of image recognition and statistical classification algorithms. Bat activity was significantly higher around landscape elements compared to open control areas. Short‐ and long‐range echolocating bats were more active in well‐connected landscapes, but optimal connectivity levels differed between the guilds. Species richness increased significantly with connectivity, while species diversity did not (Shannon's diversity index). Total bat activity was unaffected by the shape of landscape elements. Synthesis and applications. This study highlights the importance of connectivity in farmland landscapes for bats, with shorter‐range echolocating bats being particularly sensitive to habitat fragmentation. More structurally diverse landscape elements are likely to reduce population declines of bats and could improve conditions for other declining species, including birds. Activity was highest around optimal values of connectivity, which must be evaluated for the different guilds and spatially targeted for a region's habitat configuration. In a multi‐species approach, we recommend the reintroduction of structural elements to increase habitat heterogeneity should become part of agri‐environment schemes.

Bat guilds, a concept to classify the highly diverse foraging and echolocation behaviors of microchiropteran bats

Throughout evolution the foraging and echolocation behaviors as well as the motor systems of bats have been adapted to the tasks they have to perform while searching and acquiring food. When bats exploit the same class of environmental resources in a similar way, they perform comparable tasks and thus share similar adaptations independent of their phylogeny. Species with similar adaptations are assigned to guilds or functional groups. Habitat type and foraging mode mainly determine the foraging tasks and thus the adaptations of bats. Therefore, we use habitat type and foraging mode to define seven guilds. The habitat types open, edge and narrow space are defined according to the bats' echolocation behavior in relation to the distance between bat and background or food item and background. Bats foraging in the aerial, trawling, flutter detecting, or active gleaning mode use only echolocation to acquire their food. When foraging in the passive gleaning mode bats do not use echolocation but rely on sensory cues from the food item to find it. Bat communities often comprise large numbers of species with a high diversity in foraging areas, foraging modes, and diets. The assignment of species living under similar constraints into guilds identifies patterns of community structure and helps to understand the factors that underlie the organization of highly diverse bat communities. Bat species from different guilds do not compete for food as they differ in their foraging behavior and in the environmental resources they use. However, sympatric living species belonging to the same guild often exploit the same class of resources. To avoid competition they should differ in their niche dimensions. The fine grain structure of bat communities below the rather coarse classification into guilds is determined by mechanisms that result in niche partitioning.

Availability of Food for Frugivorous Bats in Lowland Amazonia: The Influence of Flooding and of River Banks

In Neotropical forests fruits are key resources for a great diversity of vertebrates, including many frugivorous bats, but little is known about the factors that determine their availability. We studied forest inundation and river banks as determinants of the spatial variation in the availability of fruits for bats in lowland Amazonia. We sampled the bat assemblage composition, fruit availability, and bat diet in terra firme upland forest and in two types of flooded forest — várzea and igapó. Two distinct frugivore bat guilds were found in both terra firme and flooded forests: (1) canopy frugivores, feeding mainly on Ficus and Cecropia, and (2) understorey frugivores that feed mainly on Vismia and Piper. Fruits consumed by the canopy guild were more abundant in the flooded forests — particularly in the nutrient-rich várzea, but those dominating the understory guild diet were most abundant in terra firme. Availability of both fruit genera most consumed by the canopy guild was greater along river banks than in the forest matrix. For the understory guild, the greater abundance of Vismia along river banks was compensated for by a higher availability of Piper in the matrix. In conclusion, both factors influence the availability of fruits, although differently for the canopy and understory guilds. The resulting differences in fruit abundance may explain variations in bat assemblages of the different forest types. River banks play a particularly important role in providing food for bats of both guilds, but are under particularly heavy human pressure.

The effects of prescribed fire on bat communities in the longleaf pine sandhills ecosystem

The historical exclusion of fire from the longleaf pine–wiregrass (sandhills) ecosystem has resulted in a tremendous net loss of this important habitat. Prescribed fire is recognized as an essential tool for the maintenance of natural successional dynamics in this system, and its positive effects on native tree, shrub, and ground-layer plant communities are well documented. However, little is known about the influence of fire periodicity on many of the wildlife species occupying these forests. Our goal was to determine the relative degree to which a forest’s structural characteristics and insect abundance and biomass influence the activity of different ecomorphological guilds of insectivorous bats and whether either of these factors was influenced by the periodicity of prescribed fire. We conducted a 2-year echolocation-monitoring study of bats in sandhills forests experiencing 3 categories of fire periodicity: 1–2 years, 3–5 years, and .8 years. We found significant differences in tree, shrub, and ground-layer characteristics among these burn-frequency categories, but few differences in abundance or biomass of most orders of nocturnal insects. However, the biomass of Lepidoptera was greatest at sites with the longest time between burns and was positively associated with fire-dependent deciduous tree and shrub densities. Bat activity below the canopy was significantly lower in the sites with .8year burn frequencies than in either of the other treatments and was positively associated with height of canopy closure (a fire-dependent variable). Species-specific activity patterns confirmed ecomorphological predictions. Small-bodied species with low wing loadings and aspect ratios replaced larger, less-maneuverable species below the canopy at sites with .8-year burn frequencies. We provide support for the hypothesis that the structural characteristics of a habitat have primacy over prey availability in habitat choice by large and fastflying species of bats. We suggest that frequency of fire is an important indirect determinant in structuring the communities of bats that forage in forests.

Morphological specialization influences nectar extraction efficiency of sympatric nectar-feeding bats

Mammals frequently use nectar as a supplementary food, while a predominantly nectarivorous lifestyle with morphological specializations for this feeding mode is rare within the class. However, Neotropical flower-visiting bats largely depend on nectar resources and show distinct adaptations to a nectar diet. Glossophagine bats form local guilds of 2-6 species that may differ distinctly in skull morphology. It is still unknown how and to what extent this morphological diversity influences the efficiency of nectar extraction and hence resource partitioning within the local bat guild. As foraging behaviour is a key factor for niche partitioning of co-existing species, we compared nectar extraction behaviour and efficiency at different flower depths among sympatric bat species with different degrees of morphological specialization (Glossophaga soricina, Leptonycteris yerbabuenae and Musonycteris harrisoni). In flight cage experiments with artificial flowers, at deeper nectar levels all species showed a distinct decrease in the amount of nectar extracted per visit and an increase in the time spent hovering at the flower, indicating increased energetic cost when foraging on longer tubed flowers. The lowest nectar extraction efficiency (g s(-1)) was found in the small G. soricina and the highest in the largest species L. yerbabuenae. However, when also considering the different energy requirements of the different-sized bat species, the morphologically most specialized M. harrisoni consistently showed the highest foraging efficiency. Our data suggest that the long rostrum and tongue of the extremely specialized M. harrisoni are probably not evolved for monopolization of co-evolved deep flowers but for allowing efficient access to the broadest range of the local chiropterophilous flower resources.

Enriching agroecosystems with fruit-producing tree species favors the abundance and richness of frugivorous and nectarivorous bats in Veracruz, Mexico

We evaluated how the abundance and richness of frugivorous and nectarivorous bat species differs among three types of common agroecosystems (diversified coffee plantations, simple coffee plantations and pastures) in Veracruz, Mexico, that represent a gradient of structural and floristic complexity. Using mixed effects models we demonstrated that both the richness and the total abundance of bats was higher in the diversified coffee plantations. We detected similar patterns on comparing the abundance of the four most abundant bat species. Neither season nor the season-agroecosystem interaction had any effect on the comparisons made. Using multiple regressions we found that the richness of plants that are useful to both people and bats had the most explanatory power for the richness and total abundance of frugivorous and nectarivorous bats, as well as for the abundance of Carollia sowelli, Glossophaga soricina and Sturnira spp. Our results indicate that agroecosystems value for conservation of fruit and nectar-eating bats increases as the fruit-bearing trees increases. For the effective conservation of these guilds of bats in tropical agroecosystems, a strategy of diversification with fruit-bearing species is highly recommended; such a strategy would benefit both agricultural producers and wildlife.

Bat diversity of Ilha da Marambaia, Southern Rio de Janeiro State, Brazil (Chiroptera, Mammalia)

Few sites have been well sampled for bats, and samplings in islands are even scarcer. Therefore, the objectives of the present study were: (1) to list the bat species of Ilha da Marambaia; (2) to compare richness, abundance and biomass of bat guilds found there; (3) to analyse abundance patterns of bat species; and (4) to compare richness, abundance and composition of the bat fauna among different kinds of environment. To capture bats we used mist nets set in five different environments, totalising 3559.2 net-hours, during 37 nights between October 2006 and August 2008. A total of 1,133 captures were accomplished, comprising 34 species from five families. The most abundant species was Molossus molossus. Frugivorous bats exhibited higher richness, abundance and biomass if compared to other guilds. Most species (N = 22) exhibited abundances between 1 to 10% of all captures. Sixteen species were restricted to just one of the environments sampled. The high richness may be attributed to sampling carried out in several environments, and to the capture of insectivorous species over water bodies.

Vegetation structure influences the vertical stratification of open- and edge-space aerial-foraging bats in harvested forests

Heavy logging leads to regrowth of dense forest, which may adversely affect the flight and foraging activities of bats. We compared insectivorous bat activity and insect abundance at three heights (understorey, subcanopy and canopy), two locations (forest and track) and three time periods (evening, night and dawn), in old and young regrowth sites in south-eastern Australia (456 detector-hours). We measured activity levels of all bats and four echolocation guilds—one open-space and three edge-space aerial-foraging guilds. Mean bat activity in the subcanopy and canopy was up to 11 times that in the understorey of forests, a pattern opposite to that of insect abundance. However, bat activity in the two upper strata was lower in young regrowth than in old regrowth. Vegetation was more cluttered in young regrowth at these upper heights (closer stems and less vertical space in the subcanopy). Mean activity on the track was 2–5 times higher than in the forest, particularly at understorey level (17 times higher for all bats), where vegetation was less cluttered (more distant understorey trees and shrubs, and less cover of ground vegetation). Time of night had little effect on bat activity. The negative response of bat guilds to increased clutter was strongest in the open-space guild and weakest in the edge-space guild with the highest frequency calls. There was an interaction between insect abundance and an index of vegetation openness, with high values of both variables producing high bat activity levels for all bats and the two highest frequency call guilds. Our results highlight the need for management practices in logged forests that increase or preserve the amount of flight and foraging space available to bats.