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Mean and standard deviation of dolphin whistles (a) and clicks rates (b) in the absence (No boat) and presence of boats (Boat). Rates were measures as the absolute amount of sounds per individual per minute (n° of sounds ind⁻¹ min⁻¹).
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Acoustic behaviour is a key component of specialized foraging tactics for many aquatic species, especially cetaceans. However, in recent decades the natural environment has been increasingly exposed to a variety of anthropogenic noise sources, with the potential to impact natural foraging specializations dependent on acoustic communication. Here we...
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... Further, dolphins that frequently cooperate with fishers exhibit smaller home ranges (Cantor et al., 2018) and higher survival rates (Bezamat et al., 2018) despite similar reproductive success (Bezamat et al., 2020). This dolphin population faces various threats, including accidental bycatch in illegal fishing gear (Bezamat et al., 2021), habitat loss (Agrelo et al., 2019), chemical pollution (Righetti et al., 2019), vessel traffic and noise pollution (Pellegrini et al., 2021). ...
... Although this is a rare occurrence, dolphins from resident populations can occasionally disperse between these ecosystems(Costa et al., 2015;Simões-Lopes & Fabian, 1999). As in Laguna, the related ecosystems face increasing acoustic and chemical pollution resulting from anthropogenic activities, potentially affecting dolphins, humans and their prey (e.g.Ferreira et al., 2021;Pellegrini et al., 2021;Righetti et al., 2019). ...
In contrast to many contemporary negative human‐nature relationships, Indigenous Peoples and Local Communities have stewarded nature through cultural practices that include reciprocal contributions for both humans and nature. A rare example is the century‐old artisanal fishery in which net‐casting fishers and wild dolphins benefit by working together, but little is known about the persistence of the social‐ecological system formed around this cultural practice.
Here, we frame the human‐dolphin cooperative fishery in southern Brazil as a social‐ecological system based on secondary data from the scientific and grey literature. To investigate the dynamics of this system, we survey the local and traditional ecological knowledge and examine potential changes in its main component—the artisanal fishers—over time and space.
Over 16 years, we conducted four interview campaigns with 188 fishers in fishing sites that are more open (accessible) or closed (restricted) to external influence. We investigated their experience, engagement and economic dependence on dolphin‐assisted fishing, as well as the learning processes and transmission of the traditional knowledge required to cooperate with dolphins.
Our qualitative data suggest that fishers using accessible and restricted fishing sites have equivalent fishing experience, but those in more restrictive sites tend to be more economically dependent on dolphins, relying on them for fishing year‐round. The traditional knowledge on how to cooperate with dolphins is mostly acquired via social learning, with a tendency for vertical learning to be frequent among fishers using sites more restrictive for outsiders. Experience, economic dependence and reliance on vertical learning seem to decrease recently, especially in the accessible site. Our quantitative analyses, however, suggest that some of these fluctuations were not significant.
Our study outlines the key components of this social‐ecological system and identifies changes in the attributes of a main component, the users. These changes, when coupled with changes in other components such as governance and resource units (fish and dolphins), can have implications for the persistence of this cultural practice and the livelihoods of Local Communities. We suggest that continuous monitoring of this system can help to safeguard the reciprocal contributions of this human‐nature relationship in years to come.
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... 325-345 2016), mainly from noise emitted by tour boats (Li et al., 2018). Dolphins use acoustic communication to search for food, and the intense noise caused by boats can reduce or interrupt this essential activity (Pellegrini et al., 2021). Added to those negative impacts, there is still the risk of ocean contamination caused by oil leaks and food/trash discarded by passengers (New et al., 2015). ...
En muchas áreas marinas protegidas de Brasil, el turismo ocurre sin planificación, como en la Reserva de Fauna Costera de Tibau do Sul (REFAUTS). En REFAUTS, los turistas utilizan el área de dos pequeñas bahías para realizar diferentes actividades y compartir espacio con delfines. Por lo tanto, el objetivo de este estudio fue caracterizar el flujo turístico en REFAUTS e identificar cuáles áreas son las más frecuentadas por los turistas. Se midió el flujo turístico en REFAUTS por medio de una encuesta realizada entre las 9:00 a. m. y las 4:00 p. m., y se identificaron las zonas más utilizadas por los turistas. REFAUTS recibe a más de 1.400 visitantes por día, la mayoría entre las 11:00 a. m. y las 3:00 p. m., lo que corresponde al tiempo activo del delfín en las bahías. En una misma zona se practican diferentes actividades, como surf, kayak, stand-up paddle, baño y avistamiento de delfines; esta superposición puede generar conflictos socioambientales y efectos negativos sobre los delfines. Se recomienda un plan de zonificación para determinar cuáles áreas deben ser utilizadas por los turistas y establecer áreas exclusivas para delfines.
... The speeds simulated by the CWJ [2.0-9.0 m/s, calculated using equation (1)] were on the lower end of the range of speeds capable for personal boats (4-25 m/ s) 37,38 and lower middle range for larger container ships and oil tankers (5-13 m/s). [39][40][41] This range of speeds was calculated from the sample depth during the experiments (28 cm). ...
Biofouling release coatings (BRCs) have received attention for their potential to limit the negative impacts of biofouling on marine shipping. The calibrated water jet (CWJ, patent # US 8,984,958 B1) can be used to study the effectiveness of BRCs as a function of ship speed. Using a balance of force and linear momentum, we examined the theory and application of the CWJ for simulating the effect of ship speed on biofilm release for surfaces fouled under (1) laboratory and (2) natural conditions. Greater fouling release corresponded with an increase in CWJ pressure and, therefore, simulated ship speed for the surfaces coated with HullKote. The effectiveness of the CWJ was further confirmed for biofilm release from glass fouled naturally by submersion in flow-through seawater. A scaling analysis confirms that the results of these small-scale experiments are applicable to larger-scale biofouling release from ship hulls. This study is the first to utilize the pressure of a CWJ to quantify biofouling release as a function of simulated ship speed.
... A reduction in the whistle emission rate was also reported for Lahille's bottlenose dolphin (Tursiops truncatus gephyreus) in Laguna, southern Brazil. Dolphins reduced the whistle rate in the presence of boats (from 0.58 to 0.35 whistles/min/animal) (Pellegrini et al. 2021).They found that larger the number of boats, the lower the whistle rate (Pellegrini et al. 2021). ...
... A reduction in the whistle emission rate was also reported for Lahille's bottlenose dolphin (Tursiops truncatus gephyreus) in Laguna, southern Brazil. Dolphins reduced the whistle rate in the presence of boats (from 0.58 to 0.35 whistles/min/animal) (Pellegrini et al. 2021).They found that larger the number of boats, the lower the whistle rate (Pellegrini et al. 2021). ...
Shipping is the principal source of anthropogenic noise in the aquatic soundscape of many coastal areas. Noise can affect temporally or permanently the physiology, behavior, and ecology of marine mammals. As noise pollution is considered to be an important threat to Guiana dolphins (Sotalia guianensis), we focused the present study in the effects of noise on occurrence and acoustic behavior in Sepetiba Bay, southeastern Brazil. We modeled the impacts of anthropogenic noise on the acoustic behavior and distribution of these dolphins in an estuarine area. We considered the acoustic parameters (maximum frequency, minimum frequency, delta frequency, duration of whistles, and whistle rates) and occurrence of Guiana dolphins as the response variables and sound exposure levels (SEL) and environmental factors (sea surface temperature, depth, bottom heterogeneity, and bottom type) as the explanatory variables. While dolphin occurrence was explained by environmental variables, mainly SST, the whistle rate was explained by SEL (contribution = 52.4%). The dolphins used noisier areas but communicated mainly in less noisy areas. Although the dolphins did not appear to avoid the noisiest areas, noise levels were the most important variable to explain the reduction in whistle rates. Our results are particularly important since they indicate the effects of noise on an endangered species living in a region with high cumulative impacts.
... Additionally, Lahille's bottlenose dolphins (T. truncatus gephyreus) emitted significantly fewer echolocation clicks in the presence of vessels in~250-m radius [17]. Moreover, melon-headed whales (Peponocephala electra) increased echolocation click source level in correlation with the level of ambient sound pressure [18]. ...
Small odontocetes produce echolocation clicks to feed and navigate, making it an essential function for their survival. Recently, the effect of vessel noise on small odontocetes behavior has attracted attention owing to increase in vessel activities; however, the effects of the surrounding environmental factor, vessel noise, and day/night on echolocation click characteristics have not been well studied. Here, we examined the effects of vessel noise and day/night on variations in echolocation clicks and click trains parameters. Passive acoustic monitoring of on-axis echolocation clicks produced by free-ranging finless porpoises (Neophocaena asiaeorientalis sunameri) was performed at two sites in Japan, Seto Inland Sea and Mikawa Bay, in June–September 2021 and March–August 2022, using A-tag and SoundTrap 300HF. Generalized Linear Model was used to elucidate the effect of vessel noise, day/night, and surrounding environmental factors (water temperature, synthetic flow velocity, and noise level) on echolocation click and click train parameters. Echolocation click and click train parameters were strongly affected by day/night, whereas the absence/presence vessel noise did not exhibit statistically significant influence. Particularly, -3 dB bandwidth was wider, click duration was shorter, and inter-click intervals in a train were shorter at night, which may facilitate information processing at night, thereby compensating for the lack of visual information. The interaction between day/night and the absence/presence of vessel noise affected the source level of finless porpoises, with higher levels observed in the absence of vessel noise during the daytime compared to other conditions at the site with low vessel traffic. Overall, these results suggest that echolocation clicks by finless porpoise were likely to fluctuate to adapt with surrounding complex environmental conditions, especially day/night.
... Similarly, acoustically active insects and amphibians may change the acoustic properties of the mating signals in response to temperature change 106 . Moreover, anthropogenic noise can induce reductions in whistles and echolocation click rates of social cetaceans 107 . ...
Contemporary rates of biodiversity decline emphasize the need for reliable ecological forecasting, but current methods vary in their ability to predict the declines of real-world populations. Acknowledging that stressor effects start at the individual level, and that it is the sum of these individual-level effects that drives populations to collapse, shifts the focus of predictive ecology away from using predominantly abundance data. Doing so opens new opportunities to develop predictive frameworks that utilize increasingly available multi-dimensional data, which have previously been overlooked for ecological forecasting. Here, we propose that stressed populations will exhibit a predictable sequence of observable changes through time: changes in individuals’ behaviour will occur as the first sign of increasing stress, followed by changes in fitness-related morphological traits, shifts in the dynamics (for example, birth rates) of populations and finally abundance declines. We discuss how monitoring the sequential appearance of these signals may allow us to discern whether a population is increasingly at risk of collapse, or is adapting in the face of environmental change, providing a conceptual framework to develop new forecasting methods that combine multi-dimensional (for example, behaviour, morphology, life history and abundance) data. The authors outline a framework for predicting animal population collapse under external stressors, based on a predictable sequence of observable changes through time.
... During sonar exposure, movement was faster and more directed, with displacements away from sonar-producing ships and prolonged intense (<10 bpm) bradycardia [54]. Animals were also more likely to cease calling during exposure [55], to reduce the whistle rates [56], or they exhibit stronger dark avoidance and scotophobia [57]. ...
Ecosystems are increasingly involved and influenced by human activities, which are ever-increasing. These activities are mainly due to vehicular, air and sea transportation, thus causing possible repercussions on the fauna that exists there. The aim of this systematic review is to investigate the possible consequences that these activities may have in the field of animal neurobehavior, with special emphasis on the species involved, the most common environment concerned, the noise source and the disturbance that is caused. This research includes articles published in the major databases (PubMed, Cochrane Library, Scopus, Embase, Web of Sciences); the online search yielded 1901 references. After selection, 49 articles (14 reviews and 35 original articles) were finally scrutinized. The main problems that were reported were in relation to movement, reproduction, offspring care and foraging. In live experiments carried out, the repercussions on the marine environment mainly concerned altered swimming, shallower descents, less foraging and an escape reaction for fear of cetaceans and fish. In birds, alterations in foraging, vocalizations and nests were noted; laboratory studies, on the other hand, carried out on small mammals, highlighted spatio-temporal cognitive alterations and memory loss. In conclusion, it appears that greater attention to all ecosystems should be given as soon as possible so as to try to achieve a balance between human activity and the well-being of terrestrial fauna.
... In this study neither ecotype changed the stereotyped whistle proportion during the recording time. The response of dolphins to vessel presence could depend on the initial behavior (May-Collado & Quiñones Lebrón, 2014), presence of calves (Guerra et al., 2014;Heiler et al., 2016) and group size (Pellegrini et al., 2021). More research is needed to investigate the reaction to the vessel presence in different social situations. ...
In the presence of vessels, dolphins have been found to change their habitat, behavior, group composition and whistle repertoire. The modification of the whistle parameters is generally considered to be a response to the engine noise. Little is known about the impact of the physical presence of vessels on dolphin acoustics. Whistle parameters of the coastal and oceanic ecotypes of common bottlenose dolphins in La Paz Bay, Mexico, were measured after the approach of the research vessel and its engine shutdown. Recordings of 10 min were made immediately after turning off the engine. For analysis, these recordings were divided from minute 0 to minute 5, and from minute 5:01 to minute 10. The whistles of the oceanic ecotype showed higher maximum, minimum and peak frequency in the second time interval compared to the first one. The whistle rate decreased in the second time interval. The whistles of the coastal ecotype showed no difference between the two time intervals. The physical presence of the research vessel could have induced a change in the whistle parameters of the oceanic dolphins until habituation to the vessel disturbance. The oceanic ecotype could increase the whistle rate and decrease the whistle frequencies to maintain acoustic contact more frequently and for longer distances. The coastal ecotype, showing no significant changes in the whistle parameters, could be more habituated to the presence of vessels and display a higher tolerance.
... A reduction in the whistle emission rate was also reported for Lahille's bottlenose dolphin (Tursiops truncatus gephyreus) in Laguna, southern Brazil. Dolphins reduced the whistle rate in the presence of boats (from 0.58 to 0.35 whistles/min/animal) (Pellegrini et al. 2021). However, using linear mixed models they found that larger the number of boats, the higher the whistle rate (Pellegrini et al. 2021). ...
... Dolphins reduced the whistle rate in the presence of boats (from 0.58 to 0.35 whistles/min/animal) (Pellegrini et al. 2021). However, using linear mixed models they found that larger the number of boats, the higher the whistle rate (Pellegrini et al. 2021). ...
Shipping is the principal source of anthropogenic noise in the aquatic soundscape of coastal areas. Noise can have temporary or permanent effects on the physiology, behavior, and ecology of the marine mammals and, as noise pollution is considered to be an important threat to Guiana dolphins ( Sotalia guianensis ), we focused on this question in the present study. We modeled the impacts of anthropogenic noise on the acoustic behavior and distribution of these dolphins. We considered the acoustic parameters and occurrence of Guiana dolphins as the response variables and Sound Exposure Levels (SEL) and environmental factors as the explanatory variables. The dolphins used noisier areas but communicated mainly in less noisy areas, given that anthropogenic noise levels induced a reduction in whistle rates. Although the dolphins did not appear to avoid the noisiest areas, their communication was impaired, and there may be areas in which communication is impracticable in this species.
... For instance, increased boat traffic seems to affect dolphins' reproductive behaviours (Lusseau, Slooten & Currey, 2006). Particularly in Laguna, boat traffic affects dolphins' acoustic behaviour during interaction with artisanal fishers (Pellegrini et al., 2021). Further studies should investigate the potential impact of boat traffic on reproduction in this population, and managing boat traffic should be considered in management actions. ...
• The small population paradigm assumes that populations with low numbers of individuals intrinsically have a high probability of extinction. The small population of Lahille’s bottlenose dolphins Tursiops truncatus gephyreus that specializes in foraging with artisanal fishers in Laguna, southern Brazil, faces human pressures including bycatch in fishing gear. The viability of this population was modelled over 30 and 100 years under different levels of bycatch, including the current scenario of two bycatches every year, two scenarios with higher incidence of bycatches and three management scenarios. The sensitivity of predicted growth rates to fixed-proportion and observed-variation changes in life history parameters was explored.
• The current scenario predicted a declining population (r = −0.014; λ = 0.986) with a high probability of extinction in the long term (PE = 0.71). A small increase in bycatches would result in a marked increase in the probability of extinction. Management scenarios seem promising, but only the zero-bycatch management scenario would make the difference between a declining and an increasing population.
• As expected for slow-growing species, population growth rate was most sensitive to proportional changes in adult female and juvenile survival. However, considering observed variation in vital rates, population dynamics were most influenced by variation in reproductive rates.
• To determine the highest priority for management action, another simulation was made of how additional threat scenarios of recognized human activities (i.e. bycatch influencing adult survival and increased underwater noise or pollution influencing calf survival) would affect population dynamics. Population growth rate was very sensitive to changes in adult bycatch (especially females), as expected, and only subtly sensitive to a reduction in calf survival.
• The current level of bycatch is unsustainable. Bycatch needs to be eliminated to maximize the probability of long-term persistence of this dolphin population. However, this population’s persistence could be threatened by natural variation in reproductive rates.
