Variation of echolocation pulse source levels and detection distances for bat assemblages across an environmental gradient: “a test of the acoustic adaptation hypothesis”

The use of multiple microphone arrays to measure echolocation pulse source levels of free-flying bats does not allow one to determine the species of the bat being recorded. However, the echolocation pulses can be assigned to species based on pulse parameters used in conjunction with a reference library of pulses, the distribution records of bat species and the identification of captured individuals sampled in the area of recording (Chapter 2). Echolocation pulses were recorded as bats emerged from their own roosts, using the multiple microphone array system. Several parameters were measured from pulses within each echolocation sequence to identify a representative pulse type for each species. These initial species assignations were confirmed through multivariate analyses so that source level of echolocation pulses could be assigned to species. Source levels used by bats impacts on the distance at which bats perceive their targets like prey in their habitats. Habitat and prevailing climatic conditions present different challenges for echolocation systems, and so the quality and content of information derived from echolocation pulse reflects these environmental challenges. Hence, echolocation pulses within or between species may vary from one habitat to the next due to variable selection pressure, resulting in local adaptation as formalised in the Acoustic Adaptation Hypothesis, which proposes that acoustic properties of the environment influence sound propagation and ultimately the evolution of echolocation pulses. To test the Acoustic Adaptation Hypothesis, I used multiple microphone arrays to measure the source levels of echolocation pulses of fourteen bat species in several bat assemblages across seven sites in different biomes in South Africa. Source levels generated from echolocation pulses, together with frequency and weather parameters were used to calculate detection distances (Chapter 3). In Chapter 4, detection distances were calculated using long-term climate data of 40 years, which is the same data used to assess whether predictive models could explain detection distances. In both chapters, the resultant detection distances were used to test the predictions of the Acoustic Adaptation Hypothesis. Results show that bats in the same assemblage used different echolocation pulse source levels and frequencies resulting to different detection distances, which differ among bat assemblages occupying different sites. Detection distance is species-specific and remained similar within species between assemblages, hence species is a better predictor of detection distances than site as indicated by Miniopterus natalensis across sites in biomes (Chapter 3). Results in Chapter 4 show that bats belonging to the same assemblage used different echolocation pulse source levels and frequencies resulting to different detection distances, which differ among bat assemblages occupying different sites under the prevailing climatic conditions. Detection distances between sites were different only in some sites, suggesting that the AAH was partially supported. Detection distance is species-specific and remained similar within species between assemblages, hence species is a better predictor of detection distances than climatic conditions as indicated by Miniopterus natalensis across sites. Detection distances for bat assemblages were correlated with temperature and longitude, whereas for Miniopterus natalensis, they were correlated with longitude, providing partial support for the Acoustic Adaptation Hypothesis. Detection distances were however not correlated with relative humidity, atmospheric pressure and latitude. Because temperature may change at different longitudes owing to diverse geographical features that affect atmospheric circulation, it suggests that temperature is the most important climatic variables that impacts echolocation and any human induced climate change that results in changes in temperature are likely to impact the survival of bats

Explosive breeding in tropical anurans: Environmental triggers, community composition and acoustic structure

Background: Anurans largely rely on acoustic communication for sexual selection and reproduction. While multiple studies have focused on the calling activity patterns of prolonged breeding assemblages, species that concentrate their reproduction in short-time windows, explosive breeders, are still largely unknown, probably because of their ephemeral nature. In tropical regions, multiple species of explosive breeders may simultaneously aggregate leading to massive, mixed and dynamic choruses. To understand the environmental triggers, the phenology and composition of these choruses, we collected acoustic and environmental data at five ponds in French Guiana during a rainy season, assessing acoustic communities before and during explosive breeding events. Results: We detected in each pond two explosive breeding events, lasting between 24 and 70 h. The rainfall during the previous 48 h was the most important factor predicting the emergence of these events. During explosive breeding events, we identified a temporal factor that clearly distinguished pre- A nd mid-explosive communities. A common pool of explosive breeders co-occurred in most of the events, namely Chiasmocleis shudikarensis, Trachycephalus coriaceus and Ceratophrys cornuta. Nevertheless, the species composition was remarkably variable between ponds and for each pond between the first and the second events. The acoustic structure of explosive breeding communities had outlying levels of amplitude and unexpected low acoustic diversity, significantly lower than the communities preceding explosive breeding events. Conclusions: Explosive breeding communities were tightly linked with specific rainfall patterns. With climate change increasing rainfall variability in tropical regions, such communities may experience significant shifts in their timing, distribution and composition. In structurally similar habitats, located in the same region without obvious barriers, our results highlight the variation in composition across explosive breeding events. The characteristic acoustic structure of explosive breeding events stands out from the circadian acoustic environment being easily detected at long distance, probably reflecting behavioural singularities and conveying heterospecific information announcing the availability of short-lived breeding sites. Our data provides a baseline against which future changes, possibly linked to climate change, can be measured, contributing to a better understanding on the causes, patterns and consequences of these unique assemblagesThis research was supported by the Labex CEBA (Centre d’Étude de la Biodiversité Amazonienne), which provided fnancial and logistic support for the data collection. JSU was supported by COLCIENCIAS (Doctoral Scholarship of the Colombian government, 2014 call #646). DLL was supported by a Global Marie S. Curie fellowship (European Commission, program H2020, EAVESTROP–661408), a postdoctoral grant Atracción de Talento Investigador (Comunidad de Madrid, CAM, Spain, 2016-T2/AMB-1722), and acknowledges funding provided by the Ministerio de Economía, Industria y Competitividad (CGL2017-88764-R, MINECO/AEI/FEDER, Spain). None of the funders had any role in the design, analysis, interpretation of results or writing the manuscrip

First characterization of toxic alkaloids and volatile organic compounds (VOCs) in the cryptic dendrobatid Silverstoneia punctiventris

Background: Poison frogs are known for the outstanding diversity of alkaloid-based chemical defences with promising therapeutic applications. However, current knowledge about chemical defences in Dendrobatoidea superfamily has two sources of bias. First, cryptic, brown-colored species have been neglected in comparison to those conspicuously colored, and second, there has been little interest in characterizing metabolites other than alkaloids mediating defensive functions. In an effort to contribute to fill the gap of knowledge about cryptic species and broadening the spectrum of compounds analyzed we have applied head-space solid phase microextraction coupled to gas chromatography and mass spectrometry (HS-SPME/GC-MS) for extracting amphibian alkaloids and volatile organic compounds (VOCs) from Silverstoneia punctiventris. Results: Using the skin from 8 specimens in 4 biological replicates we have found 33 different compounds. Twenty of them were classified as VOCs into 15 chemical classes including alkanes, alcohols, carbonyl compounds, methylpyridines, benzothiazoles, N-alkylpyrrolidines, pyrazines, and sesquiterpenoids, some of which were previously reported as repellents, defence compounds or defence pheromones in other organisms, and as sex pheromones in a treefrog. Interestingly, six of the remaining compounds were identified as alkaloids previously reported in other toxic/unpalatable dendrobatid frogs. Conclusions: This is the first report of alkaloids and VOCs found in the Silverstoneia genus, which has been assumed for decades as non-chemically defended. This study establishes HS-SPME/GC-MS as a new application for a simultaneous approach to amphibian alkaloids and VOCs in poison frogs while opens up new research questions to assess the co-occurrence of both type of compounds and to investigate the evolutionary significance of a defence gradient that includes olfactory avoidance, unpalatability, and toxicity in dendrobatids. In addition, our results show that amphibian alkaloids could have a dual function (olfactory at distance, taste by contact) never explored before neither in Silverstonaeia nor in any other dendrobatid species.Fil: Gonzalez, Mabel. Universidad de los Andes; ColombiaFil: Palacios Rodriguez, Pablo. Universidad de los Andes; ColombiaFil: Hernandez Restrepo, Jack. Universidad de los Andes; ColombiaFil: González Santoro, Marco. Universidad de los Andes; ColombiaFil: Amézquita, Adolfo. Universidad de los Andes; ColombiaFil: Brunetti, Andrés Eduardo. Universidade de Sao Paulo; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Carazzone, Chiara. Universidad de los Andes; Colombi

Exploring Animal Behavior Through Sound: Volume 1

This open-access book empowers its readers to explore the acoustic world of animals. By listening to the sounds of nature, we can study animal behavior, distribution, and demographics; their habitat characteristics and needs; and the effects of noise. Sound recording is an efficient and affordable tool, independent of daylight and weather; and recorders may be left in place for many months at a time, continuously collecting data on animals and their environment. This book builds the skills and knowledge necessary to collect and interpret acoustic data from terrestrial and marine environments. Beginning with a history of sound recording, the chapters provide an overview of off-the-shelf recording equipment and analysis tools (including automated signal detectors and statistical methods); audiometric methods; acoustic terminology, quantities, and units; sound propagation in air and under water; soundscapes of terrestrial and marine habitats; animal acoustic and vibrational communication; echolocation; and the effects of noise. This book will be useful to students and researchers of animal ecology who wish to add acoustics to their toolbox, as well as to environmental managers in industry and government

INDICES AND ECOINFORMATICS TOOLS FOR THE STUDY OF SOUNDSCAPE DYNAMICS

The study of the new field of soundscape ecology presents several research avenues to explore. In the chapters in this dissertation, I have followed several of the technical and methodological areas of the study of soundscapes. In Chapter 1, I presented the current status of the study of soundscapes as well as an overview of the contributions made in this dissertation to the field. These contributions were framed in the definition of ecological informatics (Michener and Jones 2012). In Chapter 2, I developed a web-based system to manage audio archives. This system organizes thousands of audio files while collecting the necessary metadata

Dolphin whistles can be useful tools in identifying units of conservation

Data collection and processing in the Azores was funded by Fundação para a Ciência e a Tecnologia (FCT) and Fundo Regional da Ciência e Tecnologia (FRCT), through research projects TRACE-PTDC/MAR/74071/2006 and MAPCET-M2.1.2/F/012/2011 (FEDER, the Competitiveness Factors Operational (COMPETE), QREN European Social Fund, and Pro convergencia Açores/EU Program). We also thank FCT for supporting MARE (UID/MAR/04292/2019) and OKEANOS (UIB/05634/2020), as well as for the research grants awarded to PR (SFRH/BPD/108007/2015) and CI (Project Awareness - PTDC/BIA-BMA/30514/2017). SMA is supported through project SUMMER (H2020-EU.3.2.3.1, GA 817806). Data collection by SECAC was funded by the EU LIFE programme—project LIFE INDEMARES (LIFE 07/NAT/E/000732)— and the Fundación Biodiversidad under the Spanish Ministry of Environment, Rural and Marine Affairs (project ZEC-TURSIOPS). EP was supported by a LLP/Erasmus grant 2010–2011 for collecting data in the Canary Islands.Background: Prioritizing groupings of organisms or ‘units’ below the species level is a critical issue for conservation purposes. Several techniques encompassing different time-frames, from genetics to ecological markers, have been considered to evaluate existing biological diversity at a sufficient temporal resolution to define conservation units. Given that acoustic signals are expressions of phenotypic diversity, their analysis may provide crucial information on current differentiation patterns within species. Here, we tested whether differences previously delineated within dolphin species based on i) geographic isolation, ii) genetics regardless isolation, and iii) habitat, regardless isolation and genetics, can be detected through acoustic monitoring. Recordings collected from 104 acoustic encounters of Stenella coeruleoalba, Delphinus delphis and Tursiops truncatus in the Azores, Canary Islands, the Alboran Sea and the Western Mediterranean basin between 1996 and 2012 were analyzed. The acoustic structure of communication signals was evaluated by analyzing parameters of whistles in relation to the known genetic and habitat-driven population structure. Results: Recordings from the Atlantic and Mediterranean were accurately assigned to their respective basins of origin through Discriminant Function Analysis, with a minimum 83.8% and a maximum 93.8% classification rate. A parallel pattern between divergence in acoustic features and in the genetic and ecological traits within the basins was highlighted through Random Forest analysis. Although it is not yet possible to establish a causal link between each driver and acoustic differences between basins, we showed that signal variation reflects fine-scale diversity and may be used as a proxy for recognizing discrete units. Conclusion: We recommend that acoustic analysis be included in assessments of delphinid population structure, together with genetics and ecological tracer analysis. This cost-efficient non-invasive method can be applied to uncover distinctiveness and local adaptation in other wide-ranging marine species.Publisher PDFPeer reviewe