Experimental field studies to measure behavioral responses of cetaceans to sonar

Funding was provided by a variety of military and governmental funding sources from several nations acknowledged within referenced publications, notably the US Office of Naval Research, US Navy Living Marine Resources Program, and the navies of the USA, Norway, and the Netherlands. P.L.T. acknowledges the support of the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) in the completion of this study. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions.Substantial recent progress has been made in directly measuring behavioral responses of free-ranging marine mammals to sound using controlled exposure experiments. Many studies were motivated by concerns about observed and potential negative effects of military sonar, including stranding events. Well-established experimental methods and increasingly sophisticated technologies have enabled fine-resolution measurement of many aspects of baseline behavior and responses to sonar. Studies have considered increasingly diverse taxa, but primarily odontocete and mysticete cetaceans that are endangered, particularly sensitive, or frequently exposed to sonar. This review focuses on recent field experiments studying cetacean responses to simulated or actual active military sonars in the 1 to 8 kHz band. Overall results demonstrate that some individuals of different species display clear yet varied responses, some of which have negative implications, while others appear to tolerate relatively high levels, although such exposures may have other consequences not measured. Responses were highly variable and may not be fully predictable with simple acoustic exposure metrics (e.g. received sound level). Rather, differences among species and individuals along with contextual aspects of exposure (e.g. behavioral state) appear to affect response probability. These controlled experiments provide critically needed documentation of identified behavioral responses occurring upon known sonar exposures, and they directly inform regulatory assessments of potential effects. They also inform more targeted opportunistic monitoring of potential responses of animals during sonar operations and have stimulated adaptations of field methods to consider increasingly realistic exposure scenarios and how contextual factors such as behavioral state and source proximity influence response type and probability.Publisher PDFPeer reviewe

Influence of dolphin-watching tourism vessels on the whistle emission pattern of common dolphins and bottlenose dolphins

Over the last few years there has been a significant increase in the number of dolphin-watching boats in the Algarve (Portugal), which my lead to short- and long-term impacts on the target species (e.g., common dolphin, bottlenose dolphin). In recent decades there has been a greater interest in the potential effects of anthropogenic noise on marine mammals, given the important role that sound plays in the vital functions of these organisms. Several changes in the behavior and energy expenditure of cetaceans have been documented, including impacts in the vocalization parameters of dolphins, reduction in the communication range of whistles and increase energy expenditure. In this study, the whistles characteristics of common dolphin (Delphinus delphis) and bottlenose dolphin (Tursiops truncatus) were analyzed in the presence and absence of dolphin-watching tour boats to detect potential impacts in the vocalization of dolphins. Field recordings of common dolphin and bottlenose dolphin whistles were made from June to September 2022, using a calibrated system. Dolphin behavior and group size were recorded, as well as the number of boats in a 300 m radius. A total of 15h of acoustic recording was analyzed. Overall, these results showed a significant increase in start, low and high frequency on both species when exposed to the presence of one or more dolphin-watching tour vessels. However, when analyzing the whistles, it was possible to observe a reduction in the number of inflection points in the presence of the same vessels. These changes can be a dolphin strategy to avoid sound masking and increase of energy expenditure. These findings indicate that anthropogenic impact in the form of dolphin-watching tour vessels can influence the vocalization parameters of dolphins and such changes could have an impact if they reduce the communication range of whistles or increase energy expenditure.Nas últimas décadas que tem havido um maior interesse pelos potenciais efeitos do ruído antropogénico nos mamíferos marinhos, dado o importante papel que o som desempenha nas funções vitais destas espécies. Várias mudanças no comportamento e gasto energético dos cetáceos têm sido documentadas. O impacto antropogénico resultante de tráfego marítimo pode influenciar, por exemplo, os parâmetros de vocalização dos golfinhos podendo ter efeitos a longo prazo nestes animais, nomeadamente através da redução do alcance de comunicação dos assobios ou aumento de gasto de energia. Todas as espécies de cetáceos que ocorrem em Portugal continental estão protegidas pela legislação nacional e também por regulamentação europeia (Diretiva Habitats), bem como por convenções e acordos internacionais (Berna, Bona, CITES, ACCOBAMS). Entre as medidas de proteção implementadas, inclui-se a obrigatoriedade de, nas proximidades de cetáceos, reduzir os ruídos que possam atraí-los ou perturbá-los. Em relação ao número de embarcações, não são permitidas mais de 3 plataformas num raio de 100 metros em torno de cetáceos. No entanto, o turismo dirigido a cetáceos tem vindo a crescer, em particular no Algarve, e por sua vez o número de embarcações de turismo existentes com o objetivo de observação de golfinhos. Este aumento dificulta o cumprimento das regras, e nem sempre estas são cumpridas. Atualmente, 83 empresas de turismo estão licenciadas para operar barcos de observação de golfinhos em águas continentais, das quais 49 operam ao largo da costa sul de Portugal (ICNF 2022). Em relação a 2010, há mais 35 empresas operando na região. O número de embarcações por empresa em operação varia entre 1 e 15, sendo que no total existem 131 embarcações a operar no Algarve, cada uma fazendo em média três viagens por dia. Os barcos turísticos de observação de golfinhos seguem os golfinhos por longos períodos, e muitas vezes em grande número (1-13 barcos). Com base em trabalhos anteriores, os golfinhos em tais circunstâncias são suscetíveis a ficarem stressados e esgotados. Estas alterações comportamentais podem ser detetadas, por exemplo, através da análise de padrões de frequência de assobios. A área de estudo alvo desta tese corresponde à zona costeira ocidental do Algarve (região sul de Portugal). Compreendida entre Faro e Sagres. Todos os verões, a população algarvia triplica, devido aos milhares de turistas que escolhem este destino de férias. Este aumento leva a uma maior pressão costeira nas grandes cidades, em particular em Albufeira, onde as atividades de embarcações turísticas de observação de golfinhos são muito procuradas. O objetivo deste estudo foi investigar os padrões de frequência dos assobios de golfinhos comuns (Delphinus delphis) e roazes (Tursiops truncatus) na ausência e presença de barcos de turismo de observação de golfinhos. Mais especificamente, examinaram-se as características dos assobios (por exemplo, a duração, a frequência máxima e mínima, a extenção da frequência e os pontos de inflecção), de forma a perceber se ocorrem mudanças nos padrões de emissão na presença e ausência de embarcações. Os assobios dos golfinhos-comuns e roazes são fundamentais para a comunicação entre elementos do grupo pelo que identificar e descrever potenciais efeitos nos padrões de assobios é fundamental para a conservação destas espécies. Para além do registo acústico, o comportamento dos golfinhos e o tamanho do grupo foram registados, bem como o número de barcos em um raio de 300 m. Um CTD Ruskin Concerto foi usado durante o estudo para registo da temperatura, salinidade e velocidade do som entre outros parâmetros. Os dados foram colhidos aleatoriamente, mas sempre na presença de animais, a fim de avaliar a influência das condições do mar no comportamento acústico dos golfinhos. As gravações de vocalizações de golfinhos comuns e roazes foram realizadas através de dois hidrofones calibrados, com variação de ± 1dB no intervalo de 1Hz a 28kHz. As sessões de gravação acústica ocorreram entre junho e setembro de 2022, tendo sido analisadas 5h de registos acústicos num total de 15 horas de gravações. Um total de 234 acústicas com assobios foram identificadas. As gravações recolhidas foram analisadas preliminarmente através da observação dos espectrogramas e submetidas à avaliação auditiva e visual usando o Audacity 2.4.2 a fim de identificar, categorizar e contar todos os “assobios” presentes em cada registo. Um assobio foi definido como um sinal tonal, de banda estreita, modulado com duração de 0.1 s ou mais com, pelo menos, parte da frequência fundamental acima de 3 kHz. As bandas harmônicas não foram consideradas devido às limitações das frequências superiores (26.36 kHz). Apenas a frequência fundamental de cada assobio selecionado foi medida. A plasticidade do repertório e as mudanças temporárias nas variáveis de assobio, como frequência inicial, frequência final, duração, frequência mínima, frequência máxima e número de inflexões foram depois medidas usando Raven Lite 2.0.4. Como o ruído de baixa frequência pode mascarar o componente de frequência mais baixa dos assobios, foi determinada uma estimativa do erro nas frequências medidas, tendo os assobios sido separados em três categorias de qualidade: i) má (assobio visível no espectrograma, mas muito fraco, ou sobreposto a outros sons); ii) média (assobio bem visível do início ao fim); iii) boa (assobio proeminente e dominante). Apenas assobios médios e bons foram analisados. Com base na qualidade das gravações e na relação sinal-ruído, um total de 1239 assobios foram selecionados para análise. Tanto para o golfinho comum como para o golfinho roaz, o teste de Kruskal-Wallis mostrou diferenças estatisticamente significativas para a frequência inicial, baixas e altas frequências, bem como para os pontos de infeção. A frequência inicial, baixa e alta aumentaram significativamente na presença de barcos, enquanto os pontos de inflexão diminuíram com o aumento do número de barcos de observação de golfinhos. As diferenças observadas podem resultar de uma estratégia por parte dos golfinhos para evitar a dominância do ruido das embarcações (i.e., masking), bem como o aumento do dispêndio de energia. Estes resultados indicam que o impacto antropogénico resultante da atividade de turismo de observação de golfinhos pode influenciar os parâmetros de vocalização dos animais e tais mudanças podem vir a ter impacto negativo se houver uma redução no alcance da comunicação dos assobios ou se os mesmos aumentarem os gastos de energi

Investigating Boat Noise in Wellfleet Harbor, MA

Sound plays an important role in marine environments, but growing anthropogenic noise levels in the oceans threaten marine animals’ ability to utilize essential sound signals. Anthropogenic noise pollution from military sonar, seismic airgun arrays, and shipping traffic can harm cetaceans in three ways: by causing physical injury to the animal, by masking biological important sounds in the environment, and by provoking behavioral changes. My research was part of a larger project, which aims to establish a Passive acoustic monitoring (PAM) system to detect cetacean vocalizations within and around Wellfleet Harbor in addition to possible acoustic disturbances from vessel noise. The broader study, part of research conducted by Dr. Laela Sayigh at WHOI, will attempt to determine if the vocalizations recorded can be utilized to predict mass stranding events and aid in the mitigation of such events. For my project, I analyzed underwater recordings from the harbor to determine presence of boat noise and ascertain the potential for masking. I made underwater recordings in Wellfleet Harbor, MA from 22 April, 2014 to 23 July, 2014. I analyzed the files to determine boat noise occurrence and characteristics. Overall, boat noise occurred in 32% of all recordings. I concluded that boat presence occurred frequency in Wellfleet Harbor, MA (~1/3 of the time). Boat noise occurrences followed expected day/night cycle patterns, but not expected tidal cycle patterns. Boat noise characteristics varied with deployment period, day/night cycle, and tidal cycle the observed patterns are unlikely to impact the current WHOI project. Boise noise frequency parameters, however, show some overlap with anecdotal dolphin vocalizations and could present problems for detection. I advised project managers at WHOI to adopt a precautionary approach when taking the next steps in the project, and made the following recommendations: WHOI should create boat noise filters for their detectors, conduct longer-term studies of boat noise in the harbor, pair the acoustic data with visual surveys of boats, and explore dolphin behavior in response to boat presence and noise utilizing a combination of acoustics and visual methods

Monitoring and mitigation of the sound effects of hydrocarbon exploration activities on marine mammal populations

Offshore Exploration and Production (E&P) activities, such as seismic surveys and drilling, generate sound that can affect marine mammals in different ways. These effects range from permanent or temporary auditory impacts to disturbance or behavioral changes, and communication masking. Depending on the intensity and duration of these effects, and without implementation of appropriate mitigation measures, this can result in population-level consequences. The overarching objective of this study was to advance the protection of marine mammals during the implementation of E&P activities through the following themes: (1) enhancement of the state of knowledge of risk management, (2) efficacy of mitigation, (3) advanced monitoring technology, (4) implementation of advanced industry monitoring and mitigation measures and (5) measurement of heretofore unassessed E&P activities. In this study several marine mammal monitoring and mitigation programs associated with E&P projects are presented to further advance these themes. Topics being addressed include the use of autonomous camera systems for aerial monitoring of a narwhal population, long-term photo-identification studies of western gray whales to better understand site fidelity to their summer feeding grounds, mitigation of gray whales’ behavioral responses to a seismic survey near these feeding grounds and use of Passive Acoustic Monitoring to characterize seismic pulses and drilling activity as well as marine mammal presence in remote arctic areas. A synthesis of the main findings is provided that includes identification of future research needs. Conclusions and specific recommendations are made that will contribute to our ability to assess and mitigate risks of E&P sound to marine mammals

Can baleen whales be safely live-captured for studies of their physiology?

Studying baleen whales is challenging and complex, where observation of their habitat, sensory modalities, behavior and physiology, are infrequent and brief. The biochemical and biophysical contribution of mysticetes serve a vital role in maintaining a healthy marine ecosystem, but they are facing anthropogenic threats. Before giving any indications of how these threats affect the baleen whales, it is essential to gain more knowledge of their sensory physiology, migration patterns, and energy expenditure. Previous research on mysticetes has been based on post-mortem investigation, modeling, behavioral analyses, and tagging which are advancing with time. However, some of these studies may need validation, which could be conducted with a mysticete live-capture methodology. This thesis describes an approach on how to possibly live-capture baleen whales to enable safe studies of their physiology. Therefore, my objectives aimed to 1) assess the methodology of live-capturing and restraining baleen whales by reviewing and evaluating documented attempts and those gained in own fieldwork, 2) discuss what sensory modalities baleen whales may use to navigate around nets in such settings. Furthermore, 3) I have reviewed potential studies that could be conducted on a restrained mysticete, and lastly 4) I discuss animal welfare considerations of mysticete live-capture and experimental studies. A large entrapment was created in Vestfjord, Norway, June 2021. Attempts were made to measure the distance of the baleen whales from the various nets that were designed to be better detected by different sensory methods, including recording hydrophones placed in the entrapment. These results did not give enough statistical power for concluding what sensory apparatus the cetaceans may use in detecting the entrapment set-up. We did succeed in leading baleen whales in between islets and trap them there with nets, but were unable to restrain any of them for direct measurements. The 4-year ongoing SOST minke hearing project has potential to succeed though, and may thereby represent a key to a more detailed insight into the physiology of these huge but vulnerable creatures

Acoustic Ecology of Humpback Whales (Megaptera novaeangliae) in the Hawaiian Archipelago.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017

The effects of physical, biological and anthropogenic noise on the occurrence of dolphins in the Pacific region of the Panama Canal

The main aim of this thesis was to investigate the occurrence of dolphins in Pacific waters adjacent to the Panama Canal in the context of biological, temporal and spatial factors. Acoustic data were collected at 101 sites at a range of distances and depths from the shipping region. Data were collected between March 2010 and April 2011 in a diurnal cycle over a total of 114 recording days. Received sound levels were split into 1/3 Octave bandwidths to study variation in sound pressure levels and then converted to spectrum density levels to show the sound components of the background noise in this region. Generalised Linear Models were used to relate dolphin whistle detections to temporal, spatial, environmental and acoustic variables. The major sources of background noise were biological noise from soniferous fish and snapping shrimp and anthropogenic noise from vessels characterised by mid to high frequencies produced by artisanal fishing boats. There was monthly and diurnal variation with some locations characterised by loud sounds in the mid to high frequencies at night. Whistle characteristics analysis revealed that the frequencies and range of the whistles were different to those previously reported under similar conditions. Whistles varied diurnally and in the presence of fish chorus and fishing boats. The study highlights a strong correlation between fish choruses and whistle detection. Temporal and spatial models showed that whistle detections varied monthly and in relation to fish noise and small vessel engine noise. Dolphins were distributed throughout most of the study area; however, whistle detections varied with distance from the coast. The results provide new knowledge about background noise composition in this region and provide the first information on the ecology of dolphin whistles in relation to this background noise, especially to fish chorus