Spatial distribution and foraging behaviour of Harbour Seals (Phoca vitulina) in the Wadden Sea

Movement and habitat use are essential population processes fundamental for the management and conservation of animal species. Hence, the ability to track and infer specific animal behaviours are problems that have concerned scientists for many years. Technological advances have contributed to the improvement of tracking methods over the last century. Among them, ARGOS system has become an important tool for tracking animal movement globally, however it is limited to only providing geolocation. Therefore, it is still necessary to develop a methodology capable of inferring the behaviour of an animal using the available information. The inherent complexity of animal movements and limitations in tracking systems have made necessary to develop statistical methods able to cope with such constraints. Recently, State-Space models (SSMs) have been presented as an approach capable of integrating the treatment of both limitations. In this project, it is presented a two-stages method able to determine, from movement metrics, the distribution of the animals and, more specifically, the foraging behaviour of Danish Wadden Sea population of harbour seals. Firstly, this methodology handles ARGOS inaccuracy positioning and, secondly, assigns behavioural states to each location.. Despite of the improvement of technologies, it is always challenging to estimate the spatial distribution of wildlife, but it becomes even more complicated when referring to marine life. This project aim to satisfactory applies a State Space Models to deal with biological and statistical complexities and determine the geographical distribution of the animals and site fidelity in terms of haul-out and foraging position

Implications of porpoise echolocation and dive behaviour on passive acoustic monitoring

Funding: The post-doctoral position for J.D.J.M. was funded by a FNU – Danish Natural Science Research Council grant to P.T.M. This study was also funded by the German Federal Agency for Nature Conservation via the grants “Effects of underwater noise on marine vertebrates” (Cluster 7, Z1.2-53302/2010/14) and “Under Water Noise Effects—UWE” (Project No. FKZ 3515822000). The contribution by T.A.M. was funded under the ACCURATE project (U.S. Navy Living Marine Resources Program, Contract No. N3943019C2176) and CEAUL (funded by FCT—Fundação para a Ciência e a Tecnologia, Portugal, through Project No. UIDB/00006/2020).Harbour porpoises are visually inconspicuous but highly soniferous echolocating marine predators that are regularly studied using passive acoustic monitoring (PAM). PAM can provide quality data on animal abundance, human impact, habitat use, and behaviour. The probability of detecting porpoise clicks within a given area ( P ̂ ) is a key metric when interpreting PAM data. Estimates of P ̂ can be used to determine the number of clicks per porpoise encounter that may have been missed on a PAM device, which, in turn, allows for the calculation of abundance and ideally non-biased comparison of acoustic data between habitats and time periods. However, P ̂ is influenced by several factors, including the behaviour of the vocalising animal. Here, the common implicit assumption that changes in animal behaviour have a negligible effect on P ̂ between different monitoring stations or across time is tested. Using a simulation-based approach informed by acoustic biologging data from 22 tagged harbour porpoises, it is demonstrated that porpoise behavioural states can have significant (up to 3× difference) effects on P ̂ . Consequently, the behavioural state of the animals must be considered in analysis of animal abundance to avoid substantial over- or underestimation of the true abundance, habitat use, or effects of human disturbance.Publisher PDFPeer reviewe

Ultra-high foraging rates of harbor porpoises make them vulnerable to anthropogenic disturbance

This study was partly funded by the German Federal Agency for Nature Conservation (BfN) under the contract Z1.2-5330/2010/14 and the BfN-Cluster 7 “Effects of underwater noise on marine vertebrates.” D.M.W. and P.T.M. were also supported by the Danish National Research Foundation (FNU) and the Carlsberg Foundation, and M.J. was also supported by the Marine Alliance for Science and Technology Scotland (MASTS) and by a Marie Curie-Sklodowska award.The question of how individuals acquire and allocate resources to maximize fitness is central in evolutionary ecology. Basic information on prey selection, search effort, and capture rates are critical for understanding a predator’s role in its ecosystem and for predicting its response to natural and anthropogenic disturbance. Yet, for most marine species, foraging interactions cannot be observed directly. The high costs of thermoregulation in water require that small marine mammals have elevated energy intakes compared to similar-sized terrestrial mammals [1]. The combination of high food requirements and their position at the apex of most marine food webs may make small marine mammals particularly vulnerable to changes within the ecosystem [2–4], but the lack of detailed information about their foraging behavior often precludes an informed conservation effort. Here, we use high-resolution movement and prey echo recording tags on five wild harbor porpoises to examine foraging interactions in one of the most metabolically challenged cetacean species. We report that porpoises forage nearly continuously day and night, attempting to capture up to 550 small (3–10 cm) fish prey per hour with a remarkable prey capture success rate of >90%. Porpoises therefore target fish that are smaller than those of commercial interest, but must forage almost continually to meet their metabolic demands with such small prey, leaving little margin for compensation. Thus, for these “aquatic shrews,” even a moderate level of anthropogenic disturbance in the busy shallow waters they share with humans may have severe fitness consequences at individual and population levels.PostprintPeer reviewe

High field metabolic rates of wild harbour porpoises

This study was partly funded by the German Federal Agency for Nature Conservation (BfN) under the project ‘Under Water Experiments’ (project number FKZ 3515822000) and the BfN Cluster 7 ‘Effects of underwater noise on marine vertebrates’ (Z1.2-53302/2010/14) with additional support to P.T.M. and L.R.-D. from the Danish National Research Foundation (FNU) and the Carlsberg Foundation. B.I.M. was supported by a National Science Foundation International Research Postdoctoral Fellowship (OISE – 1150123). M.J. was supported by the Marine Alliance for Science and Technology Scotland (MASTS) and by a Marie Skłodowska-Curie award.Reliable estimates of field metabolic rates (FMRs) in wild animals are essential for quantifying their ecological roles, as well as for evaluating fitness consequences of anthropogenic disturbances. Yet, standard methods for measuring FMR are difficult to use on free-ranging cetaceans whose FMR may deviate substantially from scaling predictions using terrestrial mammals. Harbour porpoises (Phocoena phocoena) are among the smallest marine mammals, and yet they live in cold, high-latitude waters where their high surface-to-volume ratio suggests high FMRs to stay warm. However, published FMR estimates of harbour porpoises are contradictory, with some studies claiming high FMRs and others concluding that the energetic requirements of porpoises resemble those of similar-sized terrestrial mammals. Here, we address this controversy using data from a combination of captive and wild porpoises to estimate the FMR of wild porpoises. We show that FMRs of harbour porpoises are up to two times greater than for similar-sized terrestrial mammals, supporting the hypothesis that small, carnivorous marine mammals in cold water have elevated FMRs. Despite the potential cost of thermoregulation in colder water, harbour porpoise FMRs are stable over seasonally changing water temperatures. Varying heat loss seems to be managed via cyclical fluctuations in energy intake, which serve to build up a blubber layer that largely offsets the extra costs of thermoregulation during winter. Such high FMRs are consistent with the recently reported high feeding rates of wild porpoises and highlight concerns about the potential impact of human activities on individual fitness and population dynamics.Publisher PDFPeer reviewe

Spatial distribution and foraging behaviour of Harbour Seals (Phoca vitulina) in the Wadden Sea

Movement and habitat use are essential population processes fundamental for the management and conservation of animal species. Hence, the ability to track and infer specific animal behaviours are problems that have concerned scientists for many years. Technological advances have contributed to the improvement of tracking methods over the last century. Among them, ARGOS system has become an important tool for tracking animal movement globally, however it is limited to only providing geolocation. Therefore, it is still necessary to develop a methodology capable of inferring the behaviour of an animal using the available information. The inherent complexity of animal movements and limitations in tracking systems have made necessary to develop statistical methods able to cope with such constraints. Recently, State-Space models (SSMs) have been presented as an approach capable of integrating the treatment of both limitations. In this project, it is presented a two-stages method able to determine, from movement metrics, the distribution of the animals and, more specifically, the foraging behaviour of Danish Wadden Sea population of harbour seals. Firstly, this methodology handles ARGOS inaccuracy positioning and, secondly, assigns behavioural states to each location.. Despite of the improvement of technologies, it is always challenging to estimate the spatial distribution of wildlife, but it becomes even more complicated when referring to marine life. This project aim to satisfactory applies a State Space Models to deal with biological and statistical complexities and determine the geographical distribution of the animals and site fidelity in terms of haul-out and foraging position

Spatial distribution and foraging behaviour of Harbour Seals (Phoca vitulina) in the Wadden Sea

Movement and habitat use are essential population processes fundamental for the management and conservation of animal species. Hence, the ability to track and infer specific animal behaviours are problems that have concerned scientists for many years. Technological advances have contributed to the improvement of tracking methods over the last century. Among them, ARGOS system has become an important tool for tracking animal movement globally, however it is limited to only providing geolocation. Therefore, it is still necessary to develop a methodology capable of inferring the behaviour of an animal using the available information. The inherent complexity of animal movements and limitations in tracking systems have made necessary to develop statistical methods able to cope with such constraints. Recently, State-Space models (SSMs) have been presented as an approach capable of integrating the treatment of both limitations. In this project, it is presented a two-stages method able to determine, from movement metrics, the distribution of the animals and, more specifically, the foraging behaviour of Danish Wadden Sea population of harbour seals. Firstly, this methodology handles ARGOS inaccuracy positioning and, secondly, assigns behavioural states to each location.. Despite of the improvement of technologies, it is always challenging to estimate the spatial distribution of wildlife, but it becomes even more complicated when referring to marine life. This project aim to satisfactory applies a State Space Models to deal with biological and statistical complexities and determine the geographical distribution of the animals and site fidelity in terms of haul-out and foraging position

Response to “Resilience of harbor porpoises to anthropogenic disturbance: Must they really feed continuously?”

Letter to the edito

Wild harbour porpoises startle and flee at low received levels from acoustic harassment device

Abstract Acoustic Harassment Devices (AHD) are widely used to deter marine mammals from aquaculture depredation, and from pile driving operations that may otherwise cause hearing damage. However, little is known about the behavioural and physiological effects of these devices. Here, we investigate the physiological and behavioural responses of harbour porpoises (Phocoena phocoena) to a commercial AHD in Danish waters. Six porpoises were tagged with suction-cup-attached DTAGs recording sound, 3D-movement, and GPS (n = 3) or electrocardiogram (n = 2). They were then exposed to AHDs for 15 min, with initial received levels (RL) ranging from 98 to 132 dB re 1 µPa (rms-fast, 125 ms) and initial exposure ranges of 0.9–7 km. All animals reacted by displaying a mixture of acoustic startle responses, fleeing, altered echolocation behaviour, and by demonstrating unusual tachycardia while diving. Moreover, during the 15-min exposures, half of the animals received cumulative sound doses close to published thresholds for temporary auditory threshold shifts. We conclude that AHD exposure at many km can evoke both startle, flight and cardiac responses which may impact blood-gas management, breath-hold capability, energy balance, stress level and risk of by-catch. We posit that current AHDs are too powerful for mitigation use to prevent hearing damage of porpoises from offshore construction