Quantifying intraspecific variation in movement behaviour of marine predators and the underlying ... more Quantifying intraspecific variation in movement behaviour of marine predators and the underlying environmental drivers is important to inform conservation management of protected species. Here, we provide the first empirical data on fine-scale movements of free-ranging harbour porpoises (Phocoena phocoena) in their natural habitat. Data were obtained from six individuals, tagged in two areas of the Danish North Sea, that were equipped with Global Positioning System (GPS) and dive recorder units (V-tags). We used multi-model inference and model averaging to evaluate the relative importance of various static and dynamic environmental conditions on the movement characteristics: speed, turning angle, dive duration, dive depth, dive wiggliness (a proxy for prey chasing behaviour), and post-dive duration. Despite substantial individual differences in horizontal and vertical movement patterns, we found that all the tracked porpoises responded similar to variation in environmental conditions and displayed movements that indicate a higher likelihood of foraging behaviour in shallower and more saline waters. Our study contributes to the identification of important feeding areas for porpoises and can be used to improve existing movement-based simulation models that aim to assess the impact of anthropogenic disturbance on harbour porpoise populations.
This is a TRACE document ("TRAnsparent and Comprehensive model Evaludation"), which provides supp... more This is a TRACE document ("TRAnsparent and Comprehensive model Evaludation"), which provides supporting evidence that our model presented in: Nabe-Nielsen J., van Beest F.M., Grimm V., Sibly R.M., Teilmann, J. & Thompson, P.M. (2018). Predicting the impacts of anthropogenic disturbances on marine populations. Conserv. Lett. was thoughtfully designed, correctly implemented, thoroughly tested, well understood, and appropriately used for its intended purpose. The rationale of this document follows: Schmolke A., Thorbek P., DeAngelis D.L., Grimm V. (2010). Ecological modelling supporting environmental decision making: a strategy for the future. Trends Ecol. Evol. 25, 479-486. and uses the updated standard terminology and document structure in:.T., Meli M., Radchuk V., Thorbek P., Railsback S.F. (2014). Towards better modelling and decision support: documenting model development, testing, and analysis using TRACE. Ecol. Modell. 280, 129-139. and Augusiak J., Van den Brink P.J., Grimm V. (2014). Merging validation and evaluation of ecological models to 'evaludation': a review of terminology and a practical approach. Ecol. Modell. 280, 117-128.
Movement is a fundamental element of animal behaviour, and it is the primary way through which an... more Movement is a fundamental element of animal behaviour, and it is the primary way through which animals respond to environmental changes. Therefore, understanding the drivers of individual movement is essential for species conservation. The endangered Saimaa ringed seal (Phoca hispida saimensis) lives landlocked in Lake Saimaa and is affected by various anthropogenic factors. Telemetry studies provide critical information but are insufficient to identify the mechanisms responsible for particular movement patterns. To better understand these mechanisms and to predict how changed movement patterns could influence the subspecies' spatial ecology, we developed an individual-based movement model. We divided the seals' daily routines into foraging and resting and explored how well the model captured observed home ranges and other movement metrics. Here we present the model, its predictions of home ranges and its sensitivity to model assumptions and parameter uncertainty. We used movement data from one individual to calibrate the model, but this resulted in poor predictions of home range sizes of five seals used for validation. This suggests that differences in movement paths not only reflect different landscape configurations but also differences among the individuals' state and personalities. Therefore, we separately re-calibrated the model to data from five individuals, reproducing their home ranges, habitat use and movement paths more accurately. Although ignoring many aspects of seal behaviour, the model can be applied as a tool to guide further data collection and analysis, study seal ecology, and evaluate the efficacy of various conservation measures.
ABSTRACT Background/Question/Methods The survival of animal populations is strongly influenced by... more ABSTRACT Background/Question/Methods The survival of animal populations is strongly influenced by the individuals’ ability to forage efficiently, yet there are few studies of how populations respond when disturbances cause animals to deviate from their natural foraging behavior. Animals that respond to disturbances by moving away are prevented from accessing the food in the disturbed areas and may also be prevented from dispersing among areas where food is available at different times of the year. Such disturbance effects may play a particularly large role for marine mammals that live in environments that are increasingly exposed to noise from ships, wind turbines, etc. In the present study we investigate how the dynamics of the harbor porpoise population (Phocoena phocoena) in the inner Danish waters is influenced by disturbances using an agent-based simulation model. In the model animal movement, and hence the animals’ ability to forage efficiently and to sustain their energy intake, is influenced by noise emitted from wind turbines and ships. The energy levels in turn affect their survival. The fine-scale movements of the simulated animals was governed by a spatial memory, which allowed the model to produce realistic movement patterns in scenarios where animals were not exposed to noise. Results/Conclusions The main results of the study were that the effects of disturbances were highly dependent on how fast the food recovered after being eaten, but that the long-term survival of the population was not jeopardized even when disturbances were simulated to have a relatively large and persistent effect on the behavior of individual animals. Porpoises were simulated to move away from noisy objects, preventing them from returning to the known food patches in that area. This resulted in decreasing energy reserves and an increasing risk of starvation. When food was simulated to recover slowly, the population effects of the disturbances was small because little food would have been available to porpoises in the known food patches even if they had been able to return. Interestingly the negative consequences of disturbances were counterbalanced by increases in the amount of food available for the remaining animals. This illustrates that it is important to consider density-dependent feedback mechanisms when evaluating the population consequences of anthropogenic disturbances.
ABSTRACT Background / Purpose: The shape, distribution and size of habitat patches affects the lo... more ABSTRACT Background / Purpose: The shape, distribution and size of habitat patches affects the long-term dynamics of populations. This can only be studied using simulation modelling.Landscape fragmentation causes reduced equilibrium population sizes and slower return from disturbances, particularly in short-dispersing species. Main conclusion: The spatial configurations of landscapes influence the long-term conservation of species, and has the largest effect on short-dispersing species and species that depend on resources in multiple patch types.
ABSTRACT Background/Question/Methods The spring migration is regarded as an energetic bottleneck ... more ABSTRACT Background/Question/Methods The spring migration is regarded as an energetic bottleneck in the annual cycle of capital breeders because they must accumulate energy and nutrients in preparation for further migration and breeding. Furthermore, because of seasonality in availability and quality of food recourses in staging areas, each stopover site offers a different set of constraints. En route to their breeding grounds, the Svalbard population of pink-footed geese stops twice, in mid- and northern Norway. Each stopover site provides different combinations of energy-rich and nutrient-rich resources. The aim of this study is to calculate the metabolizable energy intake of geese in mid Norway – the last site at which both resource types are present. The estimation of the daily energy budget was based on GPS tracking of individual birds and activity budgets derived from flock scans. Results/Conclusions The daily metabolizable energy intake was positive for all individuals and on average geese gained 1.6 more energy than they spent. However, the daily metabolizable energy was still below the maximum daily fuel deposition rate calculated for the studied species, which could be due to digestive constraints, food availability and the increased cost of flying with increased body mass. In mid-Norway habitat use by the geese was not proportional to habitat availability, and variations in energy intake were not related to the relative availability of resources with different energetic content and digestibility and the time available for feeding. Energy intake on a given day was correlated to the energy intake in the previous days. This trend was the same throughout the stopover season suggesting that foraging behaviour is a chain of decisions taken on a daily basis, although overall energy intake probably mediates decision-making. The total metabolizable energy intake was correlated with the time spent at the studied site. We conclude that mid-Norway does not currently serve as an energetic bottleneck, although the increased flying costs due to frequent disturbance and increased energy expenditure due to intra- and inter-specific competition may alter this situation in the future.
Quantifying intraspecific variation in movement behaviour of marine predators and the underlying ... more Quantifying intraspecific variation in movement behaviour of marine predators and the underlying environmental drivers is important to inform conservation management of protected species. Here, we provide the first empirical data on fine-scale movements of free-ranging harbour porpoises (Phocoena phocoena) in their natural habitat. Data were obtained from six individuals, tagged in two areas of the Danish North Sea, that were equipped with Global Positioning System (GPS) and dive recorder units (V-tags). We used multi-model inference and model averaging to evaluate the relative importance of various static and dynamic environmental conditions on the movement characteristics: speed, turning angle, dive duration, dive depth, dive wiggliness (a proxy for prey chasing behaviour), and post-dive duration. Despite substantial individual differences in horizontal and vertical movement patterns, we found that all the tracked porpoises responded similar to variation in environmental conditions and displayed movements that indicate a higher likelihood of foraging behaviour in shallower and more saline waters. Our study contributes to the identification of important feeding areas for porpoises and can be used to improve existing movement-based simulation models that aim to assess the impact of anthropogenic disturbance on harbour porpoise populations.
This is a TRACE document ("TRAnsparent and Comprehensive model Evaludation"), which provides supp... more This is a TRACE document ("TRAnsparent and Comprehensive model Evaludation"), which provides supporting evidence that our model presented in: Nabe-Nielsen J., van Beest F.M., Grimm V., Sibly R.M., Teilmann, J. & Thompson, P.M. (2018). Predicting the impacts of anthropogenic disturbances on marine populations. Conserv. Lett. was thoughtfully designed, correctly implemented, thoroughly tested, well understood, and appropriately used for its intended purpose. The rationale of this document follows: Schmolke A., Thorbek P., DeAngelis D.L., Grimm V. (2010). Ecological modelling supporting environmental decision making: a strategy for the future. Trends Ecol. Evol. 25, 479-486. and uses the updated standard terminology and document structure in:.T., Meli M., Radchuk V., Thorbek P., Railsback S.F. (2014). Towards better modelling and decision support: documenting model development, testing, and analysis using TRACE. Ecol. Modell. 280, 129-139. and Augusiak J., Van den Brink P.J., Grimm V. (2014). Merging validation and evaluation of ecological models to 'evaludation': a review of terminology and a practical approach. Ecol. Modell. 280, 117-128.
Movement is a fundamental element of animal behaviour, and it is the primary way through which an... more Movement is a fundamental element of animal behaviour, and it is the primary way through which animals respond to environmental changes. Therefore, understanding the drivers of individual movement is essential for species conservation. The endangered Saimaa ringed seal (Phoca hispida saimensis) lives landlocked in Lake Saimaa and is affected by various anthropogenic factors. Telemetry studies provide critical information but are insufficient to identify the mechanisms responsible for particular movement patterns. To better understand these mechanisms and to predict how changed movement patterns could influence the subspecies' spatial ecology, we developed an individual-based movement model. We divided the seals' daily routines into foraging and resting and explored how well the model captured observed home ranges and other movement metrics. Here we present the model, its predictions of home ranges and its sensitivity to model assumptions and parameter uncertainty. We used movement data from one individual to calibrate the model, but this resulted in poor predictions of home range sizes of five seals used for validation. This suggests that differences in movement paths not only reflect different landscape configurations but also differences among the individuals' state and personalities. Therefore, we separately re-calibrated the model to data from five individuals, reproducing their home ranges, habitat use and movement paths more accurately. Although ignoring many aspects of seal behaviour, the model can be applied as a tool to guide further data collection and analysis, study seal ecology, and evaluate the efficacy of various conservation measures.
ABSTRACT Background/Question/Methods The survival of animal populations is strongly influenced by... more ABSTRACT Background/Question/Methods The survival of animal populations is strongly influenced by the individuals’ ability to forage efficiently, yet there are few studies of how populations respond when disturbances cause animals to deviate from their natural foraging behavior. Animals that respond to disturbances by moving away are prevented from accessing the food in the disturbed areas and may also be prevented from dispersing among areas where food is available at different times of the year. Such disturbance effects may play a particularly large role for marine mammals that live in environments that are increasingly exposed to noise from ships, wind turbines, etc. In the present study we investigate how the dynamics of the harbor porpoise population (Phocoena phocoena) in the inner Danish waters is influenced by disturbances using an agent-based simulation model. In the model animal movement, and hence the animals’ ability to forage efficiently and to sustain their energy intake, is influenced by noise emitted from wind turbines and ships. The energy levels in turn affect their survival. The fine-scale movements of the simulated animals was governed by a spatial memory, which allowed the model to produce realistic movement patterns in scenarios where animals were not exposed to noise. Results/Conclusions The main results of the study were that the effects of disturbances were highly dependent on how fast the food recovered after being eaten, but that the long-term survival of the population was not jeopardized even when disturbances were simulated to have a relatively large and persistent effect on the behavior of individual animals. Porpoises were simulated to move away from noisy objects, preventing them from returning to the known food patches in that area. This resulted in decreasing energy reserves and an increasing risk of starvation. When food was simulated to recover slowly, the population effects of the disturbances was small because little food would have been available to porpoises in the known food patches even if they had been able to return. Interestingly the negative consequences of disturbances were counterbalanced by increases in the amount of food available for the remaining animals. This illustrates that it is important to consider density-dependent feedback mechanisms when evaluating the population consequences of anthropogenic disturbances.
ABSTRACT Background / Purpose: The shape, distribution and size of habitat patches affects the lo... more ABSTRACT Background / Purpose: The shape, distribution and size of habitat patches affects the long-term dynamics of populations. This can only be studied using simulation modelling.Landscape fragmentation causes reduced equilibrium population sizes and slower return from disturbances, particularly in short-dispersing species. Main conclusion: The spatial configurations of landscapes influence the long-term conservation of species, and has the largest effect on short-dispersing species and species that depend on resources in multiple patch types.
ABSTRACT Background/Question/Methods The spring migration is regarded as an energetic bottleneck ... more ABSTRACT Background/Question/Methods The spring migration is regarded as an energetic bottleneck in the annual cycle of capital breeders because they must accumulate energy and nutrients in preparation for further migration and breeding. Furthermore, because of seasonality in availability and quality of food recourses in staging areas, each stopover site offers a different set of constraints. En route to their breeding grounds, the Svalbard population of pink-footed geese stops twice, in mid- and northern Norway. Each stopover site provides different combinations of energy-rich and nutrient-rich resources. The aim of this study is to calculate the metabolizable energy intake of geese in mid Norway – the last site at which both resource types are present. The estimation of the daily energy budget was based on GPS tracking of individual birds and activity budgets derived from flock scans. Results/Conclusions The daily metabolizable energy intake was positive for all individuals and on average geese gained 1.6 more energy than they spent. However, the daily metabolizable energy was still below the maximum daily fuel deposition rate calculated for the studied species, which could be due to digestive constraints, food availability and the increased cost of flying with increased body mass. In mid-Norway habitat use by the geese was not proportional to habitat availability, and variations in energy intake were not related to the relative availability of resources with different energetic content and digestibility and the time available for feeding. Energy intake on a given day was correlated to the energy intake in the previous days. This trend was the same throughout the stopover season suggesting that foraging behaviour is a chain of decisions taken on a daily basis, although overall energy intake probably mediates decision-making. The total metabolizable energy intake was correlated with the time spent at the studied site. We conclude that mid-Norway does not currently serve as an energetic bottleneck, although the increased flying costs due to frequent disturbance and increased energy expenditure due to intra- and inter-specific competition may alter this situation in the future.
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