Date of Award
Doctor of Philosophy in Biology - (Ph.D.)
Federated Department of Biological Sciences
Gareth J. Russell
Judith S. Weis
Simon J. Garnier
Daniel E. Bunker
Large whales have historically been difficult to study and many aspects of their ecology remain unknown especially at the long -term population level. The ability to identify individual whales based on natural markings provides the opportunity to track individuals over time and space; this data may offer more insight into the ecology of whales than previously imagined. This study demonstrates use of photo-identification data to model both social structure and habitat selection, minimizing the need for invasive research and greatly increasing the sample size used in such endeavors. A conditional logistic model is written for a 20-year sightings dataset on humpback whales collected by Allied Whale research trips and on the Bar Harbor Whale Watch Company vessels, examining choice of individuals over a given landscape and incorporating the cost of movement. Habitat choices are represented by static and remotely sensed variables including bathymetry, distance from shore, and sea surface temperature. Results show significant active decisions of whales to move towards specific hotspots ~23km offshore of intermediate depth. These models are validated by systematic boat surveys conducted during two field seasons. Sightings data are also applied to social networking analyses. Association indices are calculated for each dyad of whales and preferred association is tested for through a valid Markov chain of permutations. Network structure is delineated through optimal modularity clustering producing visualizations of communities. Significant preferred companionship is seen between 94 dyads and individuals are separated into nine communities. Community structure is not entirely stable and shifts over time. Lastly, movement behavior and social structure between the whales in the northern Gulf of Maine are compared to that of the whales in the southern Gulf of Maine. The analyses listed above are run on a 26-year dataset provided by Provincetown Center for Coastal Studies on humpback whales on Stellwagen Bank. Differences are seen between northern and southern whales in use of habitat and degree of sociality. Whales in the southern aggregation are more gregarious, but have a lesser degree of long-term community structure. By applying new analytic tools to long-term observations, this research provides insights into humpback whale social behavior and ecology that should inform marine management strategies in the region.
Lubansky, Tanya Marie, "E pluribus unum: what individual whales can tell us about enigmatic species distribution and social organization" (2014). Dissertations. 101.