Narwhale with tag attached
Newswise — Perhaps you have attempted escorting a noisy canine or irritable feline to the veterinarian. Irrespective of your utmost desires, your furry companion's encounter might have been equally unenjoyable. Creatures respond to unfamiliarity in their distinct manner. The scenario remains unchanged for marine mammals like narwhals and bowhead whales upon encountering human-produced sounds like ship noises or mining explosions in the North Atlantic—or when they are ensnared by well-intentioned marine scientists seeking a deeper understanding of them.
When scientists 'tag' whales with measurement devices, the creatures respond by exhibiting peculiar and anomalous behavior. For instance, following the tagging process, they may engage in numerous atypical shallow dives and sudden movements. Such conduct can be deceptive when the objective is to observe the animal's regular and innate behavior.
The problem is getting help from an unusual corner.
"Biologists aim to comprehend animals in their natural state, but their responses manifest as unnatural behavior, introducing noise into the dataset. Consequently, a significant portion of data collected immediately after tagging whales often becomes invalid and is discarded. In this research, our team has put forth a mathematical technique employing statistical methods that precisely determines the optimal amount of data to retain," explains Lars Reiter, a PhD student from the Department of Mathematics.
Valuable for humans and animals alike
Using two statistical calculations, the researcher has developed a methodology to estimate the duration it takes for whales such as narwhals and bowhead whales to revert to their natural behavior following the tagging process. This approach not only enables the study of post-tagging behavior but also holds potential for investigating how animals react to various other disturbances.
"This research holds immense value for us as marine biologists who are dedicated to understanding the behavior and welfare of whales. It offers a standardized methodology to differentiate between natural behavior and behavior influenced by tagging. This allows us to make accurate assessments. So far, our individual estimations have proven to be remarkably accurate," explains Outi Tervo, a marine biologist from the Greenland Institute of Natural Resources, who collaborated with the mathematicians on this study.
The utilization of the statistical method enables researchers to strike a balance between discarding excessive or insufficient data. Retaining an excessive amount of data can potentially distort the research outcomes, while discarding too much data comes at a cost to both the animals and the researchers involved in the study. By finding the optimal amount of data to retain, this method ensures that the research remains accurate and comprehensive while minimizing any negative impacts on the animals and humans involved.
"It holds significant importance not just for research purposes but also from financial and animal welfare perspectives. Unnecessarily discarding data would mean subjecting more whales to the tagging experience in order to continue our research, which is fundamentally intended to benefit these magnificent creatures," emphasizes Outi Tervo. By maximizing the utility of available data, researchers can minimize the need for additional tagging procedures, reducing potential stress and impact on the well-being of the animals involved.
Idea came from a parliamentary election
Whale behavior doesn't abruptly shift from abnormal to normal with a simple movement of its tail. Instead, their behavior tends to normalize gradually, usually taking about a day, and sometimes even longer. Throughout this transitional period, a whale's behavior displays characteristics that fall on both sides of the spectrum designated as normal whale behavior. Consequently, scientists face the challenge of determining the precise point at which to delineate the transition.
Lars Reiter explains that the inspiration for his idea struck him while he was standing inside the voting booth during parliamentary elections. Drawing from the principles of the electoral system, he likens the whales' behavior, represented by data points, to a voting process in which they determine whether they fall within or outside their normal range.
Using a system of recording, scientists can assign a positive "vote" when a whale's behavior falls within the normal range and a negative "vote" when it deviates from it. By accumulating these votes, researchers can analyze the data and identify the specific point in time when the balance shifts from predominantly negative to positive votes. This transition signifies the moment when the whale's behavior normalizes according to the given criteria.
The scientists employ two methods to ascertain typical whale behavior. Firstly, they examine the whale's diving pattern, alongside its acceleration and fine motor abilities.
How to calculate the behaviour of animals statistically
Lars Reiter introduces a novel perspective that considers the significance of the activity in which a whale is involved when determining its typical energy level. This approach acknowledges the fact that whales alternate between deep hunting and quiet cruising at the surface.
Lars Reiter explains that unlike previous research, their approach does not solely focus on the average behavior of whales. Instead, they categorize a whale's activity based on its movements, considering a normal range of acceleration specific to that activity. This is accomplished by utilizing quantiles instead of averages, which enables them to concentrate on the behavioral extremes. Reiter provides an example, stating that hunting and resting represent contrasting extremes in terms of energy levels.
On the other hand, when examining the whale's diving profile, researchers analyze the pattern created by the whale's overall activities. This involves considering the combination of depth and time to evaluate whether the distribution of different dive types is representative of natural behavior. By studying the overall diving pattern, researchers can gain insights into the natural variations in the whale's diving behavior.
Wiser about the animals' hardships and better at avoiding them
The marine biologist states that employing a data-driven approach through statistical methods enables researchers to enhance their methods of tagging marine organisms with greater precision and sensitivity.
Outi Tervo highlights the findings of this study, which establish that the duration of equipment application significantly impacts the subsequent effects on animals. As a result, time limits can be established, ensuring that if the process exceeds a specified duration (X number of minutes), the whale is promptly released.
Moving away from individual estimations towards a standardized mathematical approach can lead to improved evaluations during the veterinary oversight process, which is obligatory for research projects utilizing tagging methods.
The marine biologist emphasizes that the utilization of this method will enhance the ethical approval process by incorporating more data-driven and precise assessments from veterinary inspections. This research unquestionably represents a significant stride towards promoting animal welfare.
Extra info: An important instrument for a future with less ice and more people
Climate change is causing significant alterations to the natural Arctic habitat of narwhals and bowhead whales. The shrinking of annual ice cover and the escalating human activity are encroaching upon the areas that were once exclusive to these whales. In this context, the method developed by the researchers can serve as a crucial tool, aiding in the comprehension of the resulting consequences.
Outi Tervo highlights the significance of the developed method, stating that it enables researchers to investigate the impact of diverse human activities on whales. These activities encompass external sources of noise, such as explosions or passing ships, as well as sounds and actions emitted by humans. With Lars' algorithm, a comprehensive understanding of how these factors affect the animals can be obtained, providing a clear picture of their impact.
The escalating human activity in the ocean will result in a rise in ocean noise, a matter of great concern for marine biologists due to its potential impact on large marine creatures such as narwhals, which possess exceptional sound sensitivity. Professor Susanne Ditlevsen, a co-author and supervisor, anticipates that the studies conducted and the newly developed method will gain even greater significance in the coming years, highlighting the increasing importance of understanding and mitigating the effects of ocean noise on these animals.
Susanne Ditlevsen explains that climate change is driving a surge in human activity within the Arctic whale habitats. As the ice melts, previously inaccessible areas are now reachable by humans. There is a need to evaluate the potential impacts of these activities on the whales, specifically in terms of whether they cause fear or disturbance. However, the appropriate assessment methods have not been clear until now. The newly developed methods can now be employed to determine the optimal distance from animal habitats for various activities, providing valuable insights into minimizing potential disturbances to the whales.
Facts: Statistical method with two mathematical calculations and one intersection.
The statistical method is essentially a process involving two categories of tagged data - acceleration and depth. It employs a technique of combining these data sets in a manner that determines the most favorable intersection.
1.Acceleration serves as an indicator of energy level and whale movements, often referred to as "jerks." To assess natural behavior, indicators are categorized based on whale activity. For instance, a high energy level is considered natural when associated with hunting, but not during rest periods.
2.The whale's diving behavior is evaluated using measurements of depth and the duration of their dives. Over a 40-hour period, the temporal impacts reveal a distinct pattern of various dive types, such as U-dives, where the whale remains at depth for a significant duration, or V-dives, where the whale surfaces rapidly. This pattern is then compared to the established normal values obtained from measurements taken after the 40-hour period.
3.To determine the cut-off point indicating when the whale returns to normal behavior, individual measurements are assessed as "votes" either in favor or against normal behavior. By tallying these votes, researchers identify the optimal threshold for dividing the research data into segments representing natural and influenced behavior.
About the study
The study is part of a larger research collaboration between the Greenland Institute of Natural Resources and the University of Copenhagen’s Department of Mathematics, that focuses on the Arctic's large marine mammals.
The researchers include Lars Reiter Nielsen and Susanne Ditlevsen from the University of Copenhagen, Outi M. Tervo and Mads Peter Heide-Jørgensen from the Greenland Institute of Natural Resources and Susanna B. Blackwell from Greeneridge Sciences, Inc., Santa Barbara, USA
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