Whales of the rainforest| Habitat use strategies of sympatric rorqual whales within a fjord system

by Eric Michael Keen

Institution: University of California, San Diego
Year: 2017
Keywords: Ecology; Behavioral sciences; Environmental science
Posted: 02/01/2018
Record ID: 2154930
Full text PDF: http://pqdtopen.proquest.com/#viewpdf?dispub=10256131


The energy needs of rorqual whales (f. Balaenopteridae) govern their relationship to marine habitats during the foraging season. However, their cryptic foraging strategies and extreme feeding behaviors complicate our effort to identify and protect habitats critical for rorquals. What is the relationship between rorquals and their habitat, and how must that shape conservation strategies? I addressed this question in the case of sympatric humpback (Megaptera novaeangliae) and fin whales ( Balaenoptera physalus) in the marine territory of the Gitgaat First Nation in the Kitimat Fjord System of British Columbia. For three summers (2013-2015) I studied whales, their prey, and their environment aboard the RV Bangarang using oceanographic station sampling, systematic transect surveys, and opportunistic focal follows of whales (Chapter 1). Ocean sampling demonstrated the strong coupling of water features with offshore patterns in storm forcing and regional meteorology (Chapter 2). By combining these surveys with a long-term Gitgaat dataset, area humpback whales were found to practice a structured and persistent pattern in seasonal habitat use, which demonstrates how complex and habitat-specific a rorquals habitat use can be (Chapter 3). Both humpback and fin whales were found to respond to changes in krill supply in aggregative and behavioral thresholds that are set by a combination of intrinsic energetic needs and the context of local prey supply (Chapter 4). Associations with non-prey habitat features were markedly different in the two species (Chapter 5). Humpback distribution was more closely coupled to that of their prey and other habitat features, while fin whale distribution was driven broadly by site fidelity. Novel spatial analytics were used to identify the most probable environmental cues used by foraging whales (Chapter 6). Both species were found to be particularly sensitive to the depth of prey layers, which is governed largely by oceanographic features (Chapter 7). This coupling of habitat features and feeding performance influences the competitive dynamics of rorqual whales. The findings in this case study advance general theories on marine predator ecology and conservation, and have direct implications for the management of Gitgaat territory and the identification of fin whale critical habitat in Pacific Canada.