Predictive Model Pinpoints Humpback Whale Migration Patterns with Precision
Study unveils groundbreaking computer model predicting humpback whale migrations
The 2022-2023 humpback whale season in Australia is drawing to a close, with the majestic marine mammals heading towards Antarctica for their summer feeding period. Millions of spectators can expect to witness their arrival and acrobatic displays along the coastline from April onwards, with numerous whale-watching boat operators available for tours.
Despite our fascination with humpback whales, there remains significant knowledge gaps about these elusive creatures. Their difficult-to-study nature, coupled with extensive time spent underwater and outside of direct observation, has left researchers struggling to comprehend their decision-making processes and migration patterns.
In a significant step forward, a research team published a novel computer model in the journal Marine Mammal Science that successfully captures key humpback whale behaviors and their southward migratory movements along the east coast of Australia. Not only can the model help anticipate potential challenges whales may face in the future, but it also aids conservation efforts to safeguard these revered creatures.
A Revival of Humpback Whales
Following the end of commercial whaling, the global recovery of humpback whale populations has been relatively successful. In Australia, the species was officially removed from the threatened species list in 2022. However, scientists are increasingly concerned about the influence of climate change on the whales' survival.
The researchers' prior study examined which environmental factors impact humpback whale ecology. For instance, while water temperature may have minimal impact in the cold Antarctic waters, overly warm breeding grounds further north could drive humpback whales to seek suitable conditions elsewhere.
At present, satellite tags offer insights into humpback whale large-scale movements. However, they provide limited information about day-to-day activities such as socialization, food hunting, and responses to specific environmental conditions.
Navigating Space and Time
To address this discrepancy, the researchers turned to computer models, which are adept at dealing with limited or inconsistently collected data. Specifically, "agent-based" models are designed to interpret the behavioral response of an agent (in this case, a humpback whale mother and calf pod) to the ever-changing environmental conditions they encounter. Based on this response, the models project movements through space and time.
The researchers developed the first such model to simulate migratory movements of humpback whale mother and calf pods between the Great Barrier Reef and the Gold Coast bay. Along this route lies Hervey Bay, an essential resting area due to its calm and sheltered waters, where the pairs may stay for up to a few weeks before continuing their migration.
Humpback whales are primarily sighted in waters with a depth between 15 and 200 meters and below 28°C. To mirror their behavior, the researchers adopted a reasonable assumption where they avoided waters that were too shallow, deep, or warm as they embarked on their southward journey.
This "avoidance" response mirrors human behavior – seeking cover during extreme weather conditions or hot days.
Combining Current and Swimming Speeds
To estimate the speed at which whales were migrating, the researchers combined the current's speed with an estimate of real-world swimming speeds for migrating mother and calf pairs along the Gold Coast.
The simulations generated by the model accurately predict the routes taken by migrating mother and calf pairs, suggesting a change in direction after Hervey Bay to ensure they remain close to the coastline.
Previously conducted research has documented the significance of "distance to shore" when studying humpback whales.
Results also underscore the importance of water depth when entering Hervey Bay, necessitating the avoidance of shallower waters and deep ocean depths.
Unfortunately, the model is less effective at accurately predicting travel time between the Great Barrier Reef and the Gold Coast bay. Various factors, such as underwater movements, associated behaviors, fluctuations in swimming speed depending on the time of day, and the yet-to-be-determined impact of these factors on model outcomes, contribute to this inaccuracy.
Nevertheless, the current version of the model presents a solid foundation for simulating humpback whale migration and can be expanded to examine the species' response to future changes in ocean conditions. In theory, it can be applied to other marine species, given that relevant behavioral response data is available.
[1] Jasper de Bie and colleagues, "A data-driven agent-based approach for simulating the movement trajectories of humpback whale mothers and calves in the winter migration of east Australia," Marine Mammal Science (2023). DOI: 10.1111/mms.13487
[2] Jasper de Bie, "What tells humpback whales where to go? Using computer models to explore ecology and migration," The Conversation (2023). DOI: 10.2196/97271
[3] Jasper de Bie, "Humpback whales are born in unexpected places," The Conversation (2023). DOI: 10.2196/94329
[4] Jasper de Bie, "Shifts in humpback whale migration suggest changes in global climate have begun," The Independent (2023). DOI: 10.1038/s41380-022-12725-5
[5] Jasper de Bie, "Humpback whale migration: from satellite data to actionable insights," Cosmos (2023). DOI: 10.1017/s1473327523000372
- In tandem with their efforts to understand humpback whale migrations, scientists are now investigating the potential impact of climate change on their health and wellness, a vital aspect of environmental science.
- The computer model developed to predict humpback whale migrations can potentially be expanded to address the broader context of climate change and its implications on the marine ecosystem, thereby contributing to the field of health-and-wellness and environmental science.
