The ideal long-term record: Using baleen to understand changes in whale feeding and spatial movements through time

• Main Author: Dedden, Adelaide
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UNSW, Sydney 2023
• Subjects: Baleen whale; Stable isotopes; Diet; Migration; Environmental change; Long-term data; anzsrc-for: 310305 Marine and estuarine ecology (incl. marine ichthyology); anzsrc-for: 310301 Behavioural ecology; baleen whale
• Online Access: http://hdl.handle.net/1959.4/101643; https://unsworks.unsw.edu.au/bitstreams/2b1d3d60-dc75-415d-8e85-0cdd3c524d16/download; https://doi.org/10.26190/unsworks/25350

The stable isotopes of nitrogen (δ15N) and carbon (δ13C) within whale baleen plates provide an indirect measure of individual resource use, migration strategy, and physiological changes at an interannual level. Predictable annual changes in whale dietary input and/or physiological condition (e.g., annual fasting periods) cause periodic oscillations in nitrogen and carbon stable isotope values within a baleen plate. However, there is a high degree of interannual variability in stable isotope oscillation patterns observed, both within an individual, as well as within and between populations, making interpretations difficult. This interannual variability may be driven by changes in resource utilisation, movements between different regions, and/or a difference in fasting endurance. However, methods to quantify variability in stable isotope patterns and what drives these differences each year remain unknown. In my thesis, I develop new methodology to quantify variability in baleen stable isotope patterns, and then applied these methods to examine some of the potential drivers behind baleen stable isotope variability. Overall, I show that large-scale climate cycles and oceanographic signals (like SST) are associated with changes in baleen stable isotope patterns. I also show, for some species, that baleen stable isotope patterns vary between males and females of the same species and thus, sex differences may also drive inter-individual variability within a population. Additionally, I infer the resource use and movement patterns of the smallest baleen whale, the pygmy right whale, commonly left out among comparisons with other baleen whale species. I find evidence to suggest they remain in temperate waters between southern Australia and the Subtropical Convergence, where they likely rely on euphausiid and copepod species to sustain their feeding and breeding requirements. Despite the lack of research on pygmy right whales, I show that their annual presence in coastal waters make them a relatively accessible species to ...