A Multispectral Backscattered Light Recorder of Insects’ Wingbeats

Most reported optical recorders of the wingbeat of insects are based on the so-called extinction light, which is the variation of light in the receiver due to the cast shadow of the insect\u2019s wings and main body. In this type of recording devices, the emitter uses light and is placed opposite to the receiver, which is usually a single (or multiple) photodiode. In this work, we present a different kind of wingbeat sensor and its associated recorder that aims to extract a deeper representational signal of the wingbeat event and color characterization of the main body of the insect, namely: a) we record the backscattered light that is richer in harmonics than the extinction light, b) we use three different spectral bands, i.e., a multispectral approach that aims to grasp the melanization and microstructural and color features of the wing and body of the insects, and c) we average at the receiver\u2019s level the backscattered signal from many LEDs that illuminate the wingbeating insect from multiple orientations and thus offer a smoother and more complete signal than one based on a single snapshot. We present all the necessary details to reproduce the device and we analyze many insects of interest like the bee Apis mellifera, the wasp Polistes gallicus, and some insects whose wingbeating characteristics are pending in the current literature, like Drosophila suzukii and Zaprionus, another member of the drosophilidae family

Ein Open Source Ansatz zur akustischen Detektion holzbewohnender Insekten

Bioakustik ist eine vielversprechende Methode, um Veränderungen in Ökosystemen besser zu verstehen, geeignete Massnahmen zu beschliessen und deren Wirksamkeit zu überprüfen. Diese Arbeit beschäftigt sich mit holzbewohnenden Insekten, die in Zeiten von globalen Lieferketten und Klimaveränderungen eine essenzielle Bedrohung für heimische Bäume und Ökosysteme darstellen können. Als Modellorganismus wurden kleine Holzbohrer Xyleborus saxesenii gewählt. Der Fokus liegt aber nicht auf der Biologie, sondern auf den physikalischen Grundlagen und der Technik zur bioakustischen Beobachtung von holzbewohnenden Insekten. Die physikalischen Grundlagen über Schall im Holz und der elektronischen Hilfsmittel sind in einem theoretischen Teil zusammengefasst und werden in einem Experiment umgesetzt. Ein wichtiger Anspruch hierbei war, dass die verwendeten Hard- und Softwares Open Source lizenziert sind. Der Kern der praktischen Arbeit ist die Entwicklung eines Vorverstärkers, mit dem ein piezoelektrischer Wandler als Körperschallmikrofon mit einem AudioMoth Rekorder verwendet werden kann. Die Datenauswertung wird in dieser Arbeit nur qualitativ gemacht, weitere Automatisierungen werden theoretisch diskutiert.Bioacoustics is a promising method to better understand changes in ecosystems, to decide on appropriate measures and to evaluate their effectiveness. This work focuses on wood-inhabiting insects that pose an essential threat to native trees and ecosystems in times of global supply chains and climate change. Fruit tree pinhole borer Xyleborus saxesenii were chosen as the model organism. The focus of this work is not on biology, but on physical principles and technology for bioacoustics observation of wood-inhabiting Insects. The physical basics about sound propagation in wood and the electronic instruments are summarized in a theoretical part and implemented in an experiment. An important requirement here was to use open source licensed hardware and software. The core of the practical work is the development of a preamplifier, with which a piezoelectric transducer can be used as a structure-borne sound microphone with an AudioMoth recorder. Data analysis is done only qualitatively in this work, further automations are discussed theoretically

Accessibility to protected areas increases primate hunting intensity in Bioko Island, Equatorial Guinea

Bioko is one of the most important sites for African primate conservation; yet it has seen a severe decline in its primate populations due to illegal hunting to supply a thriving wildmeat trade. The completion in 2015 of a new road bisecting the Gran Caldera Scientific Reserve (GCSR), where rugged terrain and lack of infrastructure once served as a natural barrier, further threatened this last stronghold for Bioko’s primates. Here we used passive acoustic monitoring to study factors affecting hunting patterns within GCSR through the automatic detection of shotgun sounds. Ten acoustic sensors were placed in locations that varied in terrain heterogeneity, distance to the new road, human settlements, research camps (i.e., Moraka and Moaba) and elevation. Sensors recorded continuously between January 2018 and January 2020, collecting 2671 site-days of audio. In total 596 gunshots were detected, including in the most remote areas. There were significant differences in hunting rate between areas (Kruskal-Wallis, χ2 = 102.71, df = 9, p < 0.001). We also found there were significantly fewer gunshots during 2019 than during 2018 (V = 55, p < 0.001). Occupancy modelling showed that hunting increased with decreasing terrain heterogeneity and decreasing distance to roads and villages; and decreased with increasing proximity to Research Camps. These results demonstrated that increasing accessibility increased primate hunting in GCSR, which was exacerbated by the opening of the new road. We also demonstrated that research presence was effective at reducing primate hunting. Unless strict conservation interventions are implemented, including road checkpoints, increasing biomonitoring and hunting patrols, and an island-wide, enforced ban on firearms, GCSR will see a significant decrease in primate density over the next decade, including the potential extinction of Critically Endangered Pennant’s red colobus, whose entire population is restricted to GCSR and is a primary target of hunters

Aperfeiçoamento das estratégias de amostragem e monitorização de comunidades de morcegos

Tese de Mestrado, Biologia da Conservação, 2021, Universidade de Lisboa, Faculdade de CiênciasA monitorização da vida selvagem tem-se desenvolvido consideravelmente nos últimos anos com as novas tecnologias de deteção acústica. Esta fornece diversas informações a partir dos sons produzidos pelos animais que vão desde a simples identificação da presença de espécies atá à sua abundância, posição e atividade. Entre as espécies monitorizadas acusticamente, destacam-se os morcegos que ecolocalizam. As populações de morcegos têm estado em declínio justificando a necessidade de monitorização para fins de conservação. O presente estudo tem como objetivo aperfeiçoar os métodos de amostragem, com estações acústicas, das comunidades de morcegos em três vertentes: 1) comparação entre a amostragem junto a pontos de água e em zonas secas; 2) comparação entre a amostragem com gravadores AudioMoth e Song Meter SM4BAT; 3) comparação entre amostragem usando estações de gravação duplas e individuais. Os resultados deste estudo sugerem que, numa região ou época seca, a amostragem de comunidades de morcegos utilizando estações acústicas e mais eficiente se estas forem colocadas junto de pontos de água, sendo estes os locais mais representativos. Quanto à comparação dos dois gravadores utilizados, foi identificada uma tendência na deteção do número de espécies superior com gravador SM4BAT, de maior custo, relativamente às detetadas com o AudioMoth, mais económico. Tendo em conta o elevado custo do SM4BAT, a sua escolha dependerá da avaliação entre o benefício na deteção e a limitação financeira do estudo. A utilização de um gravador AM extra por local de amostragem permitiu detetar um valor ligeiramente superior de riqueza específica de morcegos, somente para números reduzidos de gravadores e de noites de amostragem. Os resultados indicaram que só se justifica a colocação de dois gravadores por local se o número de locais disponíveis para a amostragem for reduzido e o número destes equipamentos não for limitado.Wildlife monitoring has developed considerably in recent years with new acoustic detection technologies. Recorded sounds produced by animals provide diverse information ranging from the simple identification of species to their abundance, position and activity. Among the species monitored acoustically, are the bats that echolocate. Bat populations have been declining, which justifies the need of their monitoring for conservation efforts. This study aims to improve sampling methods, with acoustic stations of bat communities following three approaches: 1) comparison between sampling near water points and in dry areas; 2) comparison between sampling with AudioMoth and Song Meter SM4BAT recorders; 3) comparison between sampling using dual and single recording stations. The results of the present study suggest that, in a dry region or season, sampling bat communities using acoustic stations is more efficient if these are placed near water points. These are the most representative locations. When comparing the two recorders used, a trend was identified in the detection of a higher number of species with the SM4BAT recorder, of higher cost, relative to those detected with the AudioMoth, which is more economical. Given the high cost of the SM4BAT, its choice will depend on the assessment between the benefit in detection and the financial limitation of the study. The use of an extra AudioMoth recorder per sampling site allowed the detection of a slightly higher value of bat specific richness, in the case of a reduced numbers of recorders and sampling nights. The results indicated that placing two recorders per site is only justified if the number of sites available for sampling is small and the number of these devices is not limited

Monitorização acústica passiva: influência do habitat e da estação do ano para a caracterização da comunidade de aves

Tese de mestrado, Biologia da Conservação, Universidade de Lisboa, Faculdade de Ciências, 2022O estudo das comunidades de aves representa uma ferramenta crucial para o conhecimento e consequente conservação dos habitats. Ao longo dos anos, as técnicas de amostragem têm evoluído e atualmente, além das técnicas tradicionais com observador, como pontos de escuta, as técnicas de monitorização acústica passiva começam a ser mais utilizadas. Em ambas as metodologias, o habitat é um dos principais fatores que influencia a deteção das aves, tal como a época do ano em que são realizadas as amostragens. Assim, para estudar a influência da estrutura do habitat e das estações do ano no potencial uso de metodologias acústicas automáticas para a monitorização das comunidades de aves, recorreu-se às duas técnicas de amostragem referidas para obter dados de dois tipos de habitat com estrutura distinta: um habitat aberto e um habitat fechado. O número de espécies detetadas foi superior nos pontos de escuta em ambos os habitats, mas com diferenças significativas relativamente às estações acústicas apenas no habitat aberto. O contributo das deteções visuais, apenas possível nos métodos dependentes de um observador, é uma possível explicação para esta diferença. Os resultados revelam ainda que, em habitats fechados, as estações acústicas podem ser úteis para complementar os registos obtidos por observadores, pois a presença da vegetação dificulta a deteção visual das aves. Adicionalmente, a diferença nas espécies detetadas pelos pontos de escuta e pelas estações acústicas foi superior no habitat aberto e no inverno, onde as aves foram mais facilmente detetadas pelo observador. Utilizou-se o Índice de Prevalência Acústica e traits acústicos e não-acústicos para tentar explicar os resultados obtidos. A técnica de amostragem automática revelou um bom desempenho, detetando praticamente todas as espécies. Contudo, esta metodologia pode tornar-se menos eficaz em determinadas situações, sendo vantajoso o uso conjunto com pontos de escuta, embora esta opção possa ser mais dispendiosa.The study of bird communities represents an important tool for the knowledge of habitats and therefore for their conservation. In recent years, sampling techniques have evolved and nowadays, in addition to observer-based traditional methods, such as point counts, passive acoustic monitoring technics are starting to be applied. Regardless of the methods, habitat type is one of the main factors influencing bird detectability, just like the time of the year. Thus, to study the influence of habitat structure and season on the potential use of automatic acoustic methods for bird monitoring, we used both sampling techniques to estimate species richness in two habitats with different structures: an open habitat and a more closed forest habitat. The number of species detected was higher in point counts in both habitat types, but with significant differences related to acoustic stations only in the open habitat. Visual detections, only possible in methods that depend on an observer, is a possible explanation for the differences. The results also revealed that the use of automatic acoustic recorders in closed habitats can be useful to complement the observer’s records, since vegetation interferes with visual bird detection by the observer. Additionally, the difference in detected species by point counts and acoustics stations was higher in the open habitat and in winter, where birds were more easily detected by the observer. The Acoustic Prevalence Index and acoustic and non-acoustic species traits were used to try to explain the results. The automatic sampling technique showed a good performance, detecting practically all species. However, this methodology may become less effective in some situations, and its use together with point counts may become advantageous, although this option may be more expensive

Acoustic monitoring of Amazonian wildlife in human-modified landscapes

Tropical forest covers just 12% of the planet’s land surface, but disproportionately host the planet’s biodiversity, including around two thirds of all terrestrial species. Amazonia retains the largest extent of remaining tropical forest globally, but just over 50% of all tropical forest loss since 2002 has been in the region. Deforestation and disturbance result in significant loss in forest biodiversity, but quantifying the exact nature of those changes can be complex. The Amazon represents a particularly challenging case in which to assess biodiversity change due to the spatiotemporal scales being assessed, because of the high proportion of rare species, and the challenging conditions for conducting biodiversity surveys in tropical forest. Ecoacoustics has been championed as a valuable tool to overcome the difficulties of monitoring in such conditions and at large spatio-temporal scales, but applied analytical methods often remain underdeveloped. In this this thesis I develop and use a range of ecoacoustic methods to help understand the impact of anthropogenic disturbance on Amazonian wildlife, using an extensive audio dataset collected from survey points spanning a degradation gradient in the Eastern Brazilian Amazon. In Chapter 2 I introduce a quick and simple method for the detection of rainfall, tested for efficacy globally and with an accompanying R package. In Chapter 3 I present a new approach to subsampling of acoustic data for manual assessment of avian biodiversity, finding that using a high number of short repeat samples can detect approximately 50% higher alpha diversity than more commonly used approaches. In Chapter 4 I assess the sensitivity and fidelity of two commonly used acoustic indices to biodiversity responses to forest disturbances, finding that measuring indices at narrower, ecologically appropriate time-frequency bins avoids problems with signal masking. In Chapter 5 I use a two-stage, random forest based method to build a multi-taxa classifier for the nocturnal avifaunal community in the study region, and use the classifier-derived data to reveal that the nocturnal bird community is largely robust to less intense forms of forest disturbance. Overall, in this thesis I demonstrate that ecoacoustics can be a highly effective method for inventorying and monitoring biodiversity in one of the most diverse and challenging regions on the planet