Echolocation of Central Amazonian ‘whispering’ phyllostomid bats: call design and interspecific variation

Phyllostomids (New World leaf-nosed bats) are the ecologically most diverse bat family and have undergone the most extensive adaptive radiation of any mammalian family. However comprehensive, multi-species studies regarding phyllostomid echolocation are scarce in the literature despite abundant ecological research. In this study, we describe the call structure and interspecific variation in call design of 40 sympatric phyllostomid species from the Central Brazilian Amazon, focussing on general patterns within genera, subfamilies and between feeding guilds. All but one species utilized short, broadband FM calls consisting of multiple harmonics. As reported for other bat families, peak frequency was negatively correlated with body mass and forearm length. Twenty-five species alternated the harmonic of maximum energy, principally between the second and third harmonic. Based on PCA, we were unable to detect any significant differences in echolocation call parameters between genera, subfamilies or different feeding guilds, confirming that acoustic surveys cannot be used to reliably monitor these species. We present Ametrida centurio as an exception to this generalized phyllostomid structure, as it is unique in producing a mono-harmonic call. Finally, we discuss several hypotheses regarding the evolutionary pressures influencing phyllostomid call structure

Bat Ensembles Differ in Response to Use Zones in a Tropical Biosphere Reserve

Biosphere reserves, designated under The United Nations Education, Scientific and Cultural Organization's (UNESCO) Man and Biosphere Programme, aim to sustainably integrate protected areas into the biological and economic landscape around them by buffering strictly protected habitats with zones of limited use. However, the effectiveness of biosphere reserves and the contribution of the different zones of use to protection is poorly known. We assessed the diversity and activity of bats in the Crocker Range Biosphere Reserve (CRBR) in Sabah, Malaysia, using harp traps, mist nets and acoustic surveys in each zone-core, buffer, transition and in agricultural plots outside of the reserve. We captured 30 species, bringing the known bat fauna of CRBR to 50 species, half of Borneo's bat species. Species composition and acoustic activity varied among zones and by foraging ensemble, with the core and buffer showing particular importance for conserving forest-dependent insectivorous bats. Frugivorous bats were found in all zones but were the most abundant and most species-rich ensemble within agricultural sites. Although sampling was limited, bat diversity and activity was low in the transition zone compared to other zones, indicating potential for management practices that increase food availability and enhance biodiversity value. We conclude that, collectively, the zones of the CRBR effectively protect diversity, but the value of the transition zone can be improved

Could Nintendo’s Animal Crossing be a tool for conservation messaging?

1. The current extinction crisis demands worldwide commitment to conservation across all sectors of society. By transcending the traditional disciplinary boundaries, conservationists can reach new audiences to communicate pro-conservation knowledge, education, and awareness messages. 2. There are approximately 2.7 billion video-gamers worldwide, with millions more joining as a result of global lockdowns. In March 2020, Animal Crossing New Horizons was released by Nintendo, fast becoming the second-best selling video game ever in Japan, and selling over 26.4 million units worldwide. Unlike many popular video games, its unique premise involves players creating an island, growing vegetation, catching wildlife, and donating fossils and species to a museum. The game has been praised for its positivity, escapism, and measurable benefits to mental wellbeing. 3. Here, we articulate how different features of the game, including the islands, their biodiversity and inhabitants, encourage players to exhibit pro-conservation behaviours and attitudes (e.g. recycling litter, or planting a diversity of flowers), as well as improving players’ knowledge about the diversity of relatively little known taxa (marine and freshwater fishes and invertebrates). We also highlight where pitfalls exist (e.g. encouraging the collection of threatened species). We principally frame these discussions in the context of Japan's cultural relationship with the natural world, including its history of insect-collecting and its management of green spaces. We conclude by outlining some recommendations about potential improvements to future releases, or for similar games, that could further promote conservation messaging. 4. This perspective sheds light on the avenues through which Animal Crossing: New Horizons encourages pro-conservation knowledge, attitudes, and behaviours of its international audience, with potential for these experiences to translate into real-world conservation actions. During a critical time in humanity’s history, video-gaming could therefore provide a huge opportunity for communicating conservation messages to billions of people worldwide

Edge effects and vertical stratification of aerial insectivorous bats across the interface of primary-secondary Amazonian rainforest

Research ArticleEdge effects, abiotic and biotic changes associated with habitat boundaries, are key drivers of community change in fragmented landscapes. Their influence is heavily modulated by matrix composition. With over half of the world’s tropical forests predicted to become forest edge by the end of the century, it is paramount that conservationists gain a better understanding of how tropical biota is impacted by edge gradients. Bats comprise a large fraction of tropical mammalian fauna and are demonstrably sensitive to habitat modification. Yet, knowledge about how bat assemblages are affected by edge effects remains scarce. Capitalizing on a whole-ecosystem manipulation in the Central Amazon, the aims of this study were to i) assess the consequences of edge effects for twelve aerial insectivorous bat species across the interface of primary and secondary forest, and ii) investigate if the activity levels of these species differed between the understory and canopy and if they were modulated by distance from the edge. Acoustic surveys were conducted along four 2-km transects, each traversing equal parts of primary and ca. 30-year-old secondary forest. Five models were used to assess the changes in the relative activity of forest specialists (three species), flexible forest foragers (three species), and edge foragers (six species). Modelling results revealed limited evidence of edge effects, except for forest specialists in the understory. No significant differences in activity were found between the secondary or primary forest but almost all species exhibited pronounced vertical stratification. Previously defined bat guilds appear to hold here as our study highlights that forest bats are more edge-sensitive than edge foraging bats. The absence of pronounced edge effects and the comparable activity levels between primary and old secondary forests indicates that old secondary forest can help ameliorate the consequences of fragmentation on tropical aerial insectivorous batsinfo:eu-repo/semantics/publishedVersio

Optimising bat bioacoustic surveys in human‐modified neotropical landscapes

During the last decades, the use of bioacoustics as a non‐invasive and cost‐effective sampling method has greatly increased worldwide. For bats, acoustic surveys have long been known to complement traditional mist‐netting, however, appropriate protocol guidelines are still lacking for tropical regions. Establishing the minimum sampling effort needed to detect ecological changes in bat assemblages (e.g., activity, composition and richness) is crucial in view of workload and project cost constraints, and because detecting such changes must be reliable enough to support effective conservation management. Using one of the most comprehensive tropical bat acoustic datasets, collected in the Amazon, we assessed the minimum survey effort required to accurately assess (1) the completeness of assemblage inventories and (2) habitat selection in fragmented forest landscapes for aerial insectivorous bats. We evaluated a combination of 20 different temporal sampling schemes, which differed regarding: (i) number of hours per night, (ii) number of nights per site and (iii) sampling only during the wet or dry season, or both. This was assessed under two different landscape scenarios: (a) in primary forest fragments embedded in a matrix of secondary forest, and (b) in the same forest fragments, but after they had been re‐isolated through clearing of the secondary forest. We found that the sampling effort required to achieve 90% inventory completeness varied considerably depending on the research aim and the landscape scenario evaluated, averaging ~80 and 10 nights before and after fragment re‐isolation, respectively. Recording for more than four hours per night did not result in a substantial reduction in the required number of sampling nights. Regarding the effects of habitat selection, except for assemblage composition, bat responses in terms of richness, diversity, and activity were similar across all sampling schemes after fragment re‐isolation. However, before re‐isolation, a minimum of four to six sampling hours per night after dusk and three to five nights of sampling per site were needed to detect significant effects that could otherwise go unnoticed. Based on our results, we propose guidelines that will aid to optimize sampling protocols for bat acoustic surveys in the Neotropics

A machine learning framework to classify Southeast Asian echolocating bats

Bats comprise a quarter of all mammal species, provide key ecosystem services and serve as effective bioindicators. Automated methods for classifying echolocation calls of free-flying bats are useful for monitoring but are not widely used in the tropics. This is particularly problematic in Southeast Asia, which supports more than 388 bat species. Here, sparse reference call databases and significant overlap among species call characteristics makes the development of automated processing methods complex. To address this, we outline a semi-automated framework for classifying bat calls in Southeast Asia and demonstrate how this can reliably speed up manual data processing. We implemented the framework to develop a classifier for the bats of Borneo and tested this at a landscape in Sabah. Borneo has a relatively well-described bat fauna, including reference calls for 52% of all 81 known echolocating species on the island. We applied machine learning to classify calls into one of four call types that serve as indicators of dominant ecological ensembles: frequency-modulated (FM; forest-specialists), constant frequency (CF; forest-specialists and edge/gap foragers), quasi-constant frequency (QCF; edge/gap foragers), and frequency-modulated quasi constant frequency (FMqCF; edge/gap and open-space foragers) calls. Where possible, we further identified calls to species/sonotype. Each classification is provided with a confidence value and a recommended threshold for manual verification. Of the 245,991 calls recorded in our test landscape, 85% were correctly identified to call type and only 10% needed manual verification for three of the call types. The classifier was most successful at classifying CF calls, reducing the volume of calls to be manually verified by over 95% for three common species. The most difficult bats to classify were those with FMqCF calls, with only a 52% reduction in files. Our framework allows users to rapidly filter acoustic files for common species and isolate files of interest, cutting the total volume of data to be processed by 86%. This provides an alternative method where species-specific classifiers are not yet feasible and enables researchers to expand non-invasive monitoring of bat species. Notably, this approach incorporates aerial insectivorous ensembles that are regularly absent from field datasets despite being important components of the bat community, thus improving our capacity to monitor bats remotely in tropical landscapes

Thresholds for adding degraded tropical forest to the conservation estate

Logged and disturbed forests are often viewed as degraded and depauperate environments compared with primary forest. However, they are dynamic ecosystems1 that provide refugia for large amounts of biodiversity2, 3, so we cannot afford to underestimate their conservation value4. Here we present empirically defined thresholds for categorizing the conservation value of logged forests, using one of the most comprehensive assessments of taxon responses to habitat degradation in any tropical forest environment. We analysed the impact of logging intensity on the individual occurrence patterns of 1,681 taxa belonging to 86 taxonomic orders and 126 functional groups in Sabah, Malaysia. Our results demonstrate the existence of two conservation-relevant thresholds. First, lightly logged forests (68%) of their biomass removed, and these are likely to require more expensive measures to recover their biodiversity value. Overall, our data confirm that primary forests are irreplaceable5, but they also reinforce the message that logged forests retain considerable conservation value that should not be overlooked

Thresholds for adding degraded tropical forest to the conservation estate

Logged and disturbed forests are often viewed as degraded and depauperate environments compared with primary forest. However, they are dynamic ecosystems1 that provide refugia for large amounts of biodiversity2,3, so we cannot afford to underestimate their conservation value4. Here we present empirically defined thresholds for categorizing the conservation value of logged forests, using one of the most comprehensive assessments of taxon responses to habitat degradation in any tropical forest environment. We analysed the impact of logging intensity on the individual occurrence patterns of 1,681 taxa belonging to 86 taxonomic orders and 126 functional groups in Sabah, Malaysia. Our results demonstrate the existence of two conservation-relevant thresholds. First, lightly logged forests (68%) of their biomass removed, and these are likely to require more expensive measures to recover their biodiversity value. Overall, our data confirm that primary forests are irreplaceable5, but they also reinforce the message that logged forests retain considerable conservation value that should not be overlooked

The use of acoustics for monitoring tropical bats in Southeast Asia

Halting the loss of biodiversity is one of our century's greatest challenges. In Southeast Asia, the biodiversity crisis is driven by unprecedented rates of forest clearance and degradation. Here, conservation efforts face the inherent complexity of trying to protect species in landscapes that also support human livelihoods. Most of our understanding of how bats are affected by land-use change in the tropics is limited to those species which can be monitored using live-trapping techniques. However, acoustic monitoring is an important survey method for monitoring the whole bat community in other regions of the world. In this thesis, advanced technological and statistical approaches are used to investigate how tropical bats respond to land-use change in Borneo. Specifically, the thesis explores the application of acoustic monitoring for bats in this region. In the first chapter, I outline how conservation zoning can be effective at protecting tropical bat diversity. To do so, I use a combination of live-trapping and acoustic monitoring to assess bat diversity and activity within The Crocker Range Biosphere Reserve compared to the surrounding agriculture. This includes demonstrating how acoustic data can be used to analyse differences in bat activity between habitats, even if it is not possible to classify calls to sonotype/species. Namely, this research highlights the importance of strict protective zones for conserving forest specialist species. Next, I refine the bat call classification process by using acoustic data manually classified sonotype/species to assess the value of conservation set-asides. These data were combined with forest structural metrics measured using airborne LiDAR to assess the effectiveness of riparian reserves (areas of native forest along waterways) for conserving bats in oil-palm landscapes. Using Bayesian occupancy modelling, I demonstrate how - unlike other components of tropical biodiversity - forest quality is more important than riparian reserve width for maintaining suitable habitat for bats. This provides important evidence for designing effective conservation policies for tropical mammals. The lack of reference call libraries and automated classification tools in Southeast Asia impedes ongoing acoustic monitoring for bats in this region. Acoustic monitoring generates large datasets - often approaching the scale of big data - which requires time and expertise to manually process. These costs limit the application of bioacoustics as a feasible method for monitoring bats in tropical regions, not least in Southeast Asia - thus, limiting our understanding of how bat communities persist in human-modified landscapes. Therefore, for the third data chapter, I focus on developing a semi-automated framework for classifying bat calls in Southeast Asia when reference libraries may be limited. As proof of concept, this viii framework is then used to develop a classifier for the bats of Borneo using reference calls for 52% of all 81 known echolocating species on the island. This classifier was developed using free software to ensure the same framework could be applied to other regions of Southeast Asia. Last, I apply the newly-developed classifier to examine patterns of bat activity in response to habitat disturbance at the Stability of Altered Forest Ecosystems Project in Sabah. The data used in this assessment represented a seven-fold increase in the number of recording hours compared to the combined effort of the previous studies. This acoustic dataset is combined with forest structural metrics measured using airborne LiDAR to assess responses across a gradient of habitat disturbance - comprising old-growth forest, logged forest, and monoculture tree plantations. In this chapter, I demonstrate how logged forests can provide important habitat for bats in human-modified landscapes, maintaining acoustic diversity and activity of many common species, particularly when compared to tree plantations. However, I also demonstrate how old-growth forest remains important for conserving forest specialist species. Collectively, in this thesis, I document how bats can benefit from conservation initiatives that protect landscape features within human-modified landscapes. Crucially however, I also demonstrate that as disturbance intensity increases, less resilient species are lost from humanmodified landscapes. Whilst I provide important empirical contributions for understanding bat responses to disturbance, there remain substantial questions about how best to conserve these species and promote sustainable land use. The pipeline and classifier provided in this thesis will help improve accessibility for future acoustic studies to address these questions in Borneo and other areas of Southeast Asia. Therefore, the findings and resources presented here are an important step towards evidence-based land management for conserving Southeast Asian bats in human-modified landscapes

Time series methods for the analysis of soundscapes and other cyclical ecological data

Biodiversity monitoring has entered an era of ‘big data’, exemplified by a near‐continuous collection of sounds, images, chemical and other signals from organisms in diverse ecosystems. Such data streams have the potential to help identify new threats, assess the effectiveness of conservation interventions, as well as generate new ecological insights. However, appropriate analytical methods are often still missing, particularly with respect to characterizing cyclical temporal patterns. Here, we present a framework for characterizing and analysing ecological responses that represent nonstationary, complex temporal patterns and demonstrate the value of using Fourier transforms to decorrelate continuous data points. In our example, we use a framework based on three approaches (spectral analysis, magnitude squared coherence, and principal component analysis) to characterize differences in tropical forest soundscapes within and across sites and seasons in Gabon. By reconstructing the underlying, cyclic behaviour of the soundscape for each site, we show how one can identify circadian patterns in acoustic activity. Soundscapes in the dry season had a complex diel cycle, requiring multiple harmonics to represent daily variation, while in the wet season there was less variance attributable to the daily cyclic patterns. Our framework can be applied to most continuous, or near‐continuous ecological data collected at a fine temporal resolution, allowing ecologists to explore patterns of temporal autocorrelation at multiple levels for biologically meaningful trends. Such methods will become indispensable as biological big data are used to understand the impact of anthropogenic pressures on biodiversity and to inform efforts to mitigate them