It\u27s Time to Listen: There is Much to be Learned from the Sounds of Tropical Ecosystems

Knowledge that can be gained from acoustic data collection in tropical ecosystems is low‐hanging fruit. There is every reason to record and with every day, there are fewer excuses not to do it. In recent years, the cost of acoustic recorders has decreased substantially (some can be purchased for under US$50, e.g., Hill et al. 2018) and the technology needed to store and analyze acoustic data is continuously improving (e.g., Corrada Bravo et al. 2017, Xie et al. 2017). Soundscape recordings provide a permanent record of a site at a given time and contain a wealth of invaluable and irreplaceable information. Although challenges remain, failure to collect acoustic data now in tropical ecosystems would represent a failure to future generations of tropical researchers and the citizens that benefit from ecological research. In this commentary, we (1) argue for the need to increase acoustic monitoring in tropical systems; (2) describe the types of research questions and conservation issues that can be addressed with passive acoustic monitoring (PAM) using both short‐ and long‐term data in terrestrial and freshwater habitats; and (3) present an initial plan for establishing a global repository of tropical recordings

Intersections of Soundscapes and Conservation: Ecologies of Sound in Naturecultures

An ecosystem is a reflection of coupled human and natural systems. A key, and less understood, interaction is with sound. Paralleling development in landscape ecology, soundscape ecology provides a diversity of measures of spatial and temporal variation in sound. Here we bridge disciplines to describe variation in soundscape measures across a gradient of novel to natural landscapes. Soundscape measures studied varied as a function of forest area but not matrix type, and season but not time. Results suggest future directions and allow practitioners to better identify management options that mitigate the impacts of noise on natural and human systems.Un écosystème est un reflet de l’appariement d’un système humain et d’un système naturel. L’une des interactions essentielles, et des moins bien comprises, se fait au moyen du son. Se développant parallèlement à l’écologie du paysage, l’écologie du paysage sonore procure une diversité de mesures de variations spatiales et temporelles du son. Ici nous établissons un pont entre les disciplines pour décrire la variation dans les mesures du paysage sonore le long d’une graduation allant des paysages nouveaux aux paysages naturels. Les mesures du paysage sonore étudiées variaient en fonction de la région forestière, mais non du type matriciel, et de la saison mais non du temps. Les résultats indiquent des orientations futures et permettent aux praticiens de mieux identifier les options de gestion qui atténuent les impacts du bruit sur les systèmes humains et naturels

Comparative micromechanics of bushcricket ears with and without a specialized auditory fovea region in the crista acustica

In some insects and vertebrate species, the specific enlargement of sensory cell epithelium facilitates the perception of particular behaviourally relevant signals. The insect auditory fovea in the ear of the bushcricket Ancylecha fenestrata (Tettigoniidae: Phaneropterinae) is an example of such an expansion of sensory epithelium. Bushcricket ears developed in convergent evolution anatomical and functional similarities to mammal ears, such as travelling waves and auditory foveae, to process information by sound. As in vertebrate ears, sound induces a motion of this insect hearing organ (crista acustica), which can be characterized by its amplitude and phase response. However, detailed micromechanics in this bushcricket ear with an auditory fovea are yet unknown. Here, we fill this gap in knowledge for bushcricket, by analysing and comparing the ear micromechanics in Ancylecha fenestrata and a bushcricket species without auditory fovea (Mecopoda elongata, Tettigoniidae: Mecopodinae) using laser-Doppler vibrometry. We found that the increased size of the crista acustica, expanded by a foveal region in A. fenestrata, leads to higher mechanical amplitudes and longer phase delays in A. fenestrata male ears. Furthermore, area under curve analyses of the organ oscillations reveal that more sensory units are activated by the same stimuli in the males of the auditory fovea-possessing species A. fenestrata. The measured increase of phase delay in the region of the auditory fovea supports the conclusion that tilting of the transduction site is important for the effective opening of the involved transduction channels. Our detailed analysis of sound-induced micromechanics in this bushcricket ear demonstrates that an increase of sensory epithelium with foveal characteristics can enhance signal detection and may also improve the neuronal encoding.Introduction. - Material and methods (animals and preparation, micro-computed tomography, laser-doppler vibrometry and sound stimulation, data analysis and statistics). - Results. - Discussio

Localizing wild chimpanzees with passive acoustics

Localizing wildlife contributes in multiple ways to species conservation. Data on animal locations can reveal elements of social behavior, habitat use, population dynamics, and be useful in calculating population density. Acoustic localization systems (ALS) are a non-invasive method widely used in the marine sciences but not well established and rarely employed for terrestrial species. We deployed an acoustic array in a mountainous environment with heterogeneous vegetation, comprised of four custom-built GPS synchronized acoustic sensors at about 500 m intervals in Issa Valley, western Tanzania, covering an area of nearly 2 km2. Our goal was to assess the precision and error of the estimated locations by conducting playback tests, but also by comparing the estimated locations of wild chimpanzee calls with their true locations obtained in parallel during follows of individual chimpanzees. We assessed the factors influencing localization error, such as wind speed and temperature, which fluctuate during the day and are known to affect sound transmission. We localized 282 playback sounds and found that the mean localization error was 27 ± 21.8 m. Localization was less prone to error and more precise during early mornings (6:30 h) compared to other periods. We further localized 22 wild chimpanzee loud calls within 52 m of the location of a researcher closely following the calling individuals. We demonstrate that acoustic localization is a powerful tool for chimpanzee monitoring, with multiple behavioral and conservation applications. Its applicability in studying social dynamics and revealing density estimation among many others, especially but not exclusively for loud calling species, provides an efficient way of monitoring populations and informing conservation plans to mediate species loss

Determining temporal sampling schemes for passive acoustic studies in different tropical ecosystems

Among different approaches to exploring and describing the ecological complexity of natural environments, soundscape analyses have recently provided useful proxies for understanding and interpreting dynamic patterns and processes in a landscape. Nevertheless, the study of soundscapes remains a new field with no internationally accepted protocols. This work provides the first guidelines for monitoring soundscapes in three different tropical areas, specifically located in the Atlantic Forest, Rupestrian fields, and the Cerrado (Brazil). Each area was investigated using three autonomous devices recording for six entire days during a period of 15 days in both the wet and dry seasons. The recordings were processed via a specific acoustic index and successively subsampled in different ways to determine the degree of information loss when reducing the number of minutes of recording used in the analyses. We describe for the first time the temporal and spectral soundscape features of three tropical environments. We test diverse programming routines to describe the costs and the benefits of different sampling designs, considering the pressing issue of storing and analyzing extensive data sets generated by passive acoustic monitoring. Schedule 5 (recording one minute of every five) appeared to retain most of the information contained in the continuous recordings from all the study areas. Less dense recording schedules produced a similar level of information only in specific portions of the day. Substantial sampling protocols such as those presented here will be useful to researchers and wildlife managers, as they will reduce time- and resource-consuming analyses, whilst still achieving reliable results

Biotic sound SNR influence analysis on acoustic indices

In recent years, passive acoustic monitoring (PAM) has become increasingly popular. Many acoustic indices (AIs) have been proposed for rapid biodiversity assessment (RBA), however, most acoustic indices have been reported to be susceptible to abiotic sounds such as wind or rain noise when biotic sound is masked, which greatly limits the application of these acoustic indices. In this work, in order to take an insight into the influence mechanism of signal-to-noise ratio (SNR) on acoustic indices, four most commonly used acoustic indices, i.e., the bioacoustic index (BIO), the acoustic diversity index (ADI), the acoustic evenness index (AEI), and the acoustic complexity index (ACI), were investigated using controlled computational experiments with field recordings collected in a suburban park in Xuzhou, China, in which bird vocalizations were employed as typical biotic sounds. In the experiments, different signal-to-noise ratio conditions were obtained by varying biotic sound intensities while keeping the background noise fixed. Experimental results showed that three indices (acoustic diversity index, acoustic complexity index, and bioacoustic index) decreased while the trend of acoustic evenness index was in the opposite direction as signal-to-noise ratio declined, which was owing to several factors summarized as follows. Firstly, as for acoustic diversity index and acoustic evenness index, the peak value in the spectrogram will no longer correspond to the biotic sounds of interest when signal-to-noise ratio decreases to a certain extent, leading to erroneous results of the proportion of sound occurring in each frequency band. Secondly, in bioacoustic index calculation, the accumulation of the difference between the sound level within each frequency band and the minimum sound level will drop dramatically with reduced biotic sound intensities. Finally, the acoustic complexity index calculation result relies on the ratio between total differences among all adjacent frames and the total sum of all frames within each temporal step and frequency bin in the spectrogram. With signal-to-noise ratio decreasing, the biotic components contribution in both the total differences and the total sum presents a complex impact on the final acoustic complexity index value. This work is helpful to more comprehensively interpret the values of the above acoustic indices in a real-world environment and promote the applications of passive acoustic monitoring in rapid biodiversity assessment

Využití bioakustických přístupů pro studium interakcí druhů a druhové bohatosti ptačích společenstev

Ptačí zpěv je jedním z nejvíce fascinujících nástrojů komunikace v živočišné říši, ať už je používán k přilákání partnerů nebo k obraně teritorií. Ve své disertační práci dokládám, že můžeme úspěšně studovat roli ptačího zpěvu v teritoriálním chování, jeho sezónní variabilitu, a nakonec i jeho roli v evolučních procesech díky moderním bioakustickým a ekoakustickým přístupům. Kombinací bioakustického přístupu s molekulárními analýzami demonstruji, že v modelovém systému dvou blízce příbuzných druhů pěvců je heterospecifická konvergence zpěvů v jejich sekundární kontaktní zóně založena na kulturním přenosu, a nikoli na mezidruhové hybridizaci a/nebo genové introgresi. Moje disertační práce dále zasahuje do tropického pásma, které se ve srovnání s pásmem mírným obecně vyznačuje méně výraznou sezónností prostředí. Studium potenciální sezonality ve zpěvní aktivitě a podílu vokalizujících druhů ptáků v tropech proto vyžaduje celoroční monitorování, což je možné i díky recentnímu vývoji automatických nahrávacích zařízení (ARU). Nejdříve se nám podařilo potvrdit, že použití nahrávek z ARU poskytuje ve specifických podmínkách prostředí tropického lesa velmi podobné odhady skladby společenstva, druhové bohatosti a početnosti jako tradiční terénní metody bodového sčítání. To mi umožnilo na Kamerunské hoře...Birdsong is one of the most fascinating communication tools in the animal kingdom, whether it is used for attracting a mate or in territory defense. In my dissertation, I present evidence that we can successfully study the role of birdsong in territorial behaviour, its seasonal variability, and ultimately its role in evolutionary processes thanks to modern bioacoustic and ecoacoustic approaches. By combining the bioacoustic approach with molecular analyses, I demonstrate that in the model system of two closely related passerine species, the heterospecific song convergence in their secondary contact zone is based on cultural transmission, and not on interspecific hybridisation and/or gene introgression. My dissertation further extends into the tropical zone, which is generally characterized by less pronounced environmental seasonality compared to the temperate zone. The study of potential seasonality in singing activity and the proportion of vocalizing species in this zone therefore requires year-round monitoring, which is possible thanks to the quite recent development of automated recording units (ARU). First, we confirmed that using ARU provides very similar estimates of community composition, species richness, and abundance to traditional field methods (point counts) in the specific conditions...Department of EcologyKatedra ekologieFaculty of SciencePřírodovědecká fakult

Caracterización y monitoreo de aves y paisajes sonoros en tres macrohábitats de la región de La Mojana.

Las comunidades bióticas son específicas a los hábitats y ecosistemas que ocupan y la comunicación acústica refleja esta especificidad. La confluencia de la biofonía, geofonía y antropofonía genera lo que se conoce como paisaje sonoro. Las características acústicas de estos paisajes cambian según los patrones de la biodiversidad. Por lo tanto, el estudio de los paisajes sonoros permite evaluar y monitorear la heterogeneidad del paisaje, teniendo en cuenta a las comunidades de fauna vocalmente activa (insectos, aves, mamíferos y anfibios), asociadas a diferentes gradientes ecológicos. Los humedales del área de La Mojana, en el departamento de Sucre, presentan grandes procesos de transformación por cambio en el uso de la tierra hacia sistemas productivos, lo que ha llevado a la degradación de los bosques, pérdida de cobertura boscosa, fragmentación y degradación de servicios ecosistémicos. Buscando mitigar los efectos negativos que conlleva la perdida de los ecosistemas naturales, se están estableciendo diferentes faenas de restauración en tres macrohábitats asociados a humedales: Zapal, Ciénaga y vegetación riparia. Con el fin de evaluar el estado de las comunidades de aves y paisajes sonoros de los tres macrohábitats en la fase inicial de la restauración, hicimos grabaciones manuales, censos de aves y utilizamos grabadoras automáticas, para determinar aquellos índices de diversidad acústica que mejor correlación tuvieran entre los ambientes sonoros grabados manualmente con los índices tradicionales basados en censos de aves. Utilizamos los índices con mejor desempeño para evaluar los paisajes sonoros de los tres macrohábitats. A través de una correlación de Spearman entre 12 índices de riqueza de especies y 5 índices de diversidad acústica, escogimos aquellos índices de diversidad acústica que presentaron significancia estadística y correlación positiva con los índices basados en los censos de aves. Los índices de complejidad acústica (ACI), de diversidad acústica (ADI) y el índice de bioacústica (BI), fueron los que mejor desempeño tuvieron. EA través de un análisis discriminante de los paisajes sonoros de los macrohábitats evaluados, encontramos que hay las características espectrales permiten categorizar cada macrohábitat en diferentes momentos del día. Esto sugiere que cada macrohábitat tiene una forma acústica característica, que podría utilizarse para estudiar la heterogeneidad en el paisaje.Bogotá, ColombiaPrograma Gestión Territorial de la Biodiversida

Sensitive aerial hearing within a noisy nesting soundscape in a deep-diving seabird, the common murre Uria aalge

Diving seabirds face a combination of sound exposure in marine and terrestrial environments due to increasing human encroachment on coastal ecosystems. Yet the sound-sensitivity and sensory ecology of this threatened group of animals is largely unknown, complicating effective management and conservation. Here, we characterize aspects of the acoustic ecology of the common murre Uria aalge, one of the deepest diving alcid seabirds. Electrophysiological aerial hearing thresholds were measured for 12 wild, nesting individuals and compared to conspecific vocalizations and short-term aerial soundscape dynamics of their cliff nesting habitat. Auditory responses were measured from 0.5 to 6 kHz, with a lowest mean threshold of 30 dB at 2 kHz and generally sensitive hearing from 1 to 3.5 kHz. The short-term murre nesting soundscape contained biotic sounds from con- and heterospecific avifauna; broadband sounds levels of 56-69 dB re: 20 µPa rms (0.1-10 kHz) were associated with both diel and tidal-cycle factors. Five murre vocalization types showed dominant spectral emphasis at or below the region of best hearing. Common murre hearing appears to be less sensitive than a related alcid, the Atlantic puffin Fratercula arctica, but more sensitive than other non-alcid diving birds described to date, suggesting that adaptations for deep diving have not caused a loss of the species’ hearing ability above water. Overall, frequencies of common murre hearing and vocalization overlap with many anthropogenic noise sources, indicating that the species is susceptible to disturbance from a range of noise types

Determining temporal sampling schemes for passive acoustic studies in different tropical ecosystems

Among different approaches to exploring and describing the ecological complexity of natural environments, soundscape analyses have recently provided useful proxies for understanding and interpreting dynamic patterns and processes in a landscape. Nevertheless, the study of soundscapes remains a new field with no internationally accepted protocols. This work provides the first guidelines for monitoring soundscapes in three different tropical areas, specifically located in the Atlantic Forest, Rupestrian fields, and the Cerrado (Brazil). Each area was investigated using three autonomous devices recording for six entire days during a period of 15 days in both the wet and dry seasons. The recordings were processed via a specific acoustic index and successively subsampled in different ways to determine the degree of information loss when reducing the number of minutes of recording used in the analyses. We describe for the first time the temporal and spectral soundscape features of three tropical environments. We test diverse programming routines to describe the costs and the benefits of different sampling designs, considering the pressing issue of storing and analyzing extensive data sets generated by passive acoustic monitoring. Schedule 5 (recording one minute of every five) appeared to retain most of the information contained in the continuous recordings from all the study areas. Less dense recording schedules produced a similar level of information only in specific portions of the day. Substantial sampling protocols such as those presented here will be useful to researchers and wildlife managers, as they will reduce time- and resource-consuming analyses, whilst still achieving reliable results