Biofonía en un ruidoso fragmento de bosque urbano tropical

Anthropogenic noise, which is part of an urban soundscape, can negatively affect the behaviour of wild animals. Here we investigated how biophony (animal sounds) was affected by noise in an urban Brazilian forest fragment. Our hypothesis was that noise and biophony would differ between the border and the centre of the forest fragment (i.e., lower biophony predicted in noisy areas). Two passive acoustic monitoring devices were used to record soundscapes one week per month, 24 hour per day, from May to July 2012. The Acoustic Complexity Index (ACI) was used to quantify biophony and the Power Spectral Density (PSD) to quantify urban noise. PSD and ACI were higher on the border than in the centre of the fragment. PSD was lower in July, while the ACI did not significantly vary between months. Noise levels were also higher on the border. Conversely, potential species richness was higher in the centre of the forest fragment. Higher biophony at noisy sites can be interpreted as behavioural responses of species for communicating in noisy areas. Alternatively, they could be the result of species segregation by degree of vocal plasticity or due to differences in composition of communities.El ruido antropogénico, que forma parte de un paisaje sonoro urbano, puede afectar negativamente el comportamiento de los animales En este estudio investigamos cómo la biofonía (sonidos de animales) se vió afectada por el ruido antropogénico en un fragmento de bosque urbano brasileño. Nuestra hipótesis es que el ruido y la biofonía difiren entre el borde y el centro del fragmento de bosque (es decir, una menor biofonía en áreas ruidosas). Se usaron dos dispositivos de monitoreo acústico pasivo para grabar paisajes sonoros una semana al mes, 24 horas al día, de mayo a julio de 2012. El índice de complejidad acústica (ACI) se usó para cuantificar la biofonía y la densidad espectral de potencia (PSD) para cuantificar el ruido urbano. Se obtucieron mayores valores de PSD y ACI en el borde que en el centro del fragmento. La PSD fue menor en julio, mientras que el ACI no varió significativamente entre meses. Los niveles de ruido también fueron más altos en el borde, mientras que la riqueza potencial de especies fue mayor en el centro del fragmento de bosque. Una mayor biofonía en áreas ruidosas puede ser interpretada como el efecto de respuestas conductuales de las especies con el fin de establecer una comunicación efectiva. Alternativamente, podrían ser el resultado de la segregación de especies por grado de plasticidad vocal o debido a diferencias en la composición de las comunidades

THE SOUNDSCAPE APPROACH FOR THE ASSESSMENT AND CONSERVATION OF MEDITERRANEAN LANDSCAPES: PRINCIPLES AND CASE STUDIES

Abstract The fine-grained mosaic of natural and human-modified patches that characterizes the Mediterranean region has created a multifaceted system that is difficult to investigate using traditional ecological techniques. In this context, sounds have been found to be the optimum model to provide indirect and timely information about the state of ecosystems. The sonic nature of the environment (the soundscape) represents an important component of the landscape, and the new discipline of soundscape ecology has recently been shown to have appropriate tools for investigating the complexity of the environment. In the last decade, technological advances in the acoustic field have led researchers to carry out wide-scale and long-term ecological research using new and efficient tools, such as digital low cost sound recorders, and autonomous software and metrics. Particularly in the Mediterranean region, where land transformation occurs at a very rapid rate, soundscape analysis may represent an efficient tool with which to:1) track transformations in the community balance, 2) indicate the most acoustically complex parts (bioacoustic hotspots) of the land mosaic, 3) prevent environmental degradation, and 4) decide whether protection or restoration actions are most appropriate. Conserving the quality of Mediterranean sounds means preserving the natural dynamics of its animal populations and also involves maintaining the cultural heritage, human identity, and the spiritual values of the area

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

The soundscape ecology: A new frontier of landscape research and its application to island and coastal systems

Islands and mainland coastal ranges are fragile systems rich in biological endemisms and ecological peculiarities. In these environments, the cultural heritage that represents an important component of the overall ecological complexity is under attack from human pressures (urban sprawl, logistics, fish farming and mass tourism). Among the most valuable resources pertaining to these environments, the overall emerging sounds (the soundscape) play a relevant role with respect to the maintenance of the sense of a place and its cultural value. The study of the soundscape requires an epistemology based mainly on the cognitive landscape perspective, and within this theoretical framework, the General Theory of Resources, the Eco-field hypothesis and the soundtope model are also important components. Among the methods used in soundscape ecology, the analysis of the frequency bins of the acoustic spectrogram can provide proxies for understanding and interpreting acoustic patterns and processes in action across a landscape. The description of a case-study from a Tyrrhenian coastal system of Northern Italy, via the use of dedicated software and metrics, briefly illustrates the potential of soundscape ecology, which is entirely suitable for achieving a better understanding of the dynamics of island and mainland coastal systems

Sonic environment and vegetation structure: A methodological approach for a soundscape analysis of a Mediterranean maqui

Hereinwe present one of the first attempts to couple the complexity of vegetation and topographic featureswith the sonic environment to understand the distribution of bird species and individuals in their habitat. To achieve this, the sonic features of a bird community were studied during the spring and early summer of 2011 in a Mediterranean maqui located on the western slope of a remote hanging valley that is dominated by Erica arborea, Quercus ilex and Arbutus unedo. Species composition, height, vertical foliage profile, canopy density and dispersion of vegetation were utilized as probable proxies for the sonic patterns. The acoustic activity of birds was collected through the use of a regular matrix of 20 audio recorders, spaced 25 m apart, which were placed following the topographic isoclines. The sonic complexity of the soundscape was evaluated using the Acoustic Complexity Index (ACI),which is a recently developed metric. The PCA applied to the vegetation parameters revealed two principal distinguishing factors, which we were able to define as “vegetation density and structure” and “species segregation.” Moreover, the results show that, even in the case of sampling sites that are very close together, sonic patterns vary across the season, highlighting the great variability of the soundscape and confirming the adequacy of the sampling scale of 25 m adopted in this study. The topographic features do not seem to be connected to the sonic environment. The main sonic complexity was foundwhere the vegetation was taller and denser, especially where E. arboreawas the dominant species. Although this proves that acoustic dynamics can be linked to vegetation structure, even on a small scale, a consistent element of sonic variability cannot be explained by vegetation patterns alone, and a soundtope hypothesis must be invoked

Application of a recently introduced index for acoustic complexity to an avian soundscape with traffic noise

An altered acoustic environment can have severe consequences for natural communities, especially for species that use acoustic signals to communicate and achieve breeding success. Numerous studies have focused on traffic noise disturbance, but the possible causes of road effects are intercorrelated and the literature on noise qua noise is sometimes contradictory. To provide further empirical data in this regard, the authors investigated the spatio-temporal variability of the singing dynamics of an avian community living in an acoustic context altered by traffic noise. Fieldwork was carried out in a wood of Turkey oaks (central Italy) bordered on one side by a main road. The soundscape was examined by positioning eight digital recorders, distributed in two transects perpendicular to the road, and recording between 6:30 and 8.30 a.m. for 12 continuous sessions. The acoustic complexity index was used to obtain a quantification of singing dynamics, which were positively correlated with traffic noise. This may indicate that birds try to propagate their signals with greater emphasis (e.g., amplified redundancy or loudness of the songs) to override the masking effect of noise. Nevertheless, an ecotonal effect could have influenced the correlation results, with this enhanced dynamic possibly being due to a more densely populated environment

Acoustic patterns of an invasive species: the Red-billed Leiothrix (Leiothrix luteaScopoli 1786) in a Mediterranean shrubland

The Red-billed Leiothrix (Leiothrix lutea) is an invasive species which has recently been found to be locally abundant in eastern Liguria (Italy). The song production of this bird was recorded over the course of an entire year (2011) and evaluated using both aural information and applying innovative automatic processing metrics. Our findings revealed that the Red-billed Leiothrix has loud vocalizations that are heard for most of the year, including in July and August when other birds are silent. Its song production has been estimated to amount to 37% of the sounds uttered by the entire bird community. The next most vocal species are the European Robin (36%), the Common Blackbird (18%), the Subalpine Warbler (5%) and the Sardinian Warbler (1%). The Red-billed Leiothrix can be seen as a new acoustically dominant species and, consequently, a potential modifier of the soundscape patterns of the indigenous bird community. The modification of acoustic traits in the repertoire of both indigenous species and the Red-billed Leiothrix is to be expected according to a co-evolution hypothesis

Marine soundscape as an additional biodiversity monitoring tool: A case study from the Adriatic Sea (Mediterranean Sea)

Acoustic monitoring can provide essential information on marine environments, including insights into ecosystem functioning and marine biodiversity monitoring. However, data on species acoustic behavior and ecoacoustics studies in the Mediterranean Sea are still extremely scarce and this limits our ability to use soundscape features in monitoring studies. Here we present the results of a soundscape investigation conducted on shallow hard bottoms of the Adriatic Sea (Central Mediterranean basin). We report the presence of diverse circadian rhythms recorded in two different months, July and September. A power spectral density (PSD) was used to assess the overall spectral composition over time, and the Acoustic Complexity Index (ACI), was identified as a proxy for marine sounds of biological origin. The dominant component of the biological soundscape was composed of snapping shrimps and fishes. Spectral characteristics varied significantly both daily and between the two months. For frequencies>620 Hz (i.e., associated to snapping shrimp activity), both PSD and ACI were higher in July than in September. The same circadian rhythm was reported in both sampling periods, with the presence of snaps for 24 h a day, but with significantly lower intensity during daylight hours and pitches at the beginning and ending of the night. At lower frequencies (i.e.,<620 Hz), fish vocalizations mostly occurred during the night. Higher values of ACI were recorded during the night in both months, whereas the presence of anthropogenic noise caused opposite results in PSD levels. Noise was associated with higher PSD and ACI at the peak frequency of the snaps, suggesting a stimulation in snapping activity. Our findings provide new insights on the marine biological soundscape and on the potential use of ecoacoustics in future monitoring programs.Acoustic monitoring can provide essential information on marine environments, including insights into ecosystem functioning and marine biodiversity monitoring. However, data on species acoustic behavior and ecoacoustics studies in the Mediterranean Sea are still extremely scarce and this limits our ability to use soundscape features in monitoring studies. Here we present the results of a soundscape investigation conducted on shallow hard bottoms of the Adriatic Sea (Central Mediterranean basin). We report the presence of diverse circadian rhythms recorded in two different months, July and September. A power spectral density (PSD) was used to assess the overall spectral composition over time, and the Acoustic Complexity Index (ACI), was identified as a proxy for marine sounds of biological origin. The dominant component of the biological soundscape was composed of snapping shrimps and fishes. Spectral characteristics varied significantly both daily and between the two months. For frequencies>620 Hz (i.e., associated to snapping shrimp activity), both PSD and ACI were higher in July than in September. The same circadian rhythm was reported in both sampling periods, with the presence of snaps for 24 h a day, but with significantly lower intensity during daylight hours and pitches at the beginning and ending of the night. At lower frequencies (i.e.,<620 Hz), fish vocalizations mostly occurred during the night. Higher values of ACI were recorded during the night in both months, whereas the presence of anthropogenic noise caused opposite results in PSD levels. Noise was associated with higher PSD and ACI at the peak frequency of the snaps, suggesting a stimulation in snapping activity. Our findings provide new insights on the marine biological soundscape and on the potential use of ecoacoustics in future monitoring programs

A Complexity-Entropy Based Approach for the Detection of Fish Choruses

Automated acoustic indices to infer biological sounds from marine recordings have produced mixed levels of success. The use of such indices in complex marine environments, dominated by several anthropogenic and geophonic sources, have yet to be understood fully. In this study, we introduce a noise resilient method based on complexity-entropy (hereafter named C-H) for the detection of biophonic sounds originating from fish choruses. The C-H method was tested on data collected in Changhua and Miaoli (Taiwan) during the spring in both 2016 and 2017. Miaoli was exposed to continual shipping activity, which led to an increase of ~10 dB in low frequency ambient noise levels (5–500 Hz). The acoustic dataset was successively analyzed via the acoustic complexity index, the acoustic diversity index and the bioacoustic index. The C-H method was found to be strongly correlated with fish chorusing (Pearson correlation: rH &lt; −0.9; rC &gt; 0.89), and robust to noise originating from shipping activity or natural sources, such as wind and tides (rH and rC were between 0.22 and −0.19). Other indices produced lower or null correlations with fish chorusing due to missed identification of the choruses or sensitivity to other sound sources. In contrast to most acoustic indices, the C-H method does not require a prior setting of frequency and amplitude thresholds, and is therefore, more user friendly to untrained technicians. We conclude that the use of the C-H method has potential implications in the efficient detection of fish choruses for management or conservation purposes and could help with overcoming the limitations of acoustic indices in noisy marine environments