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Application of novel methods in conservation physiology for understanding cases of baleen whale mortalities

Fernandez Ajo, Alejandro Apolo (2021) Application of novel methods in conservation physiology for understanding cases of baleen whale mortalities. Doctoral thesis, Northern Arizona University.

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Recovery and conservation of populations of large whales is particularly important to the marine environment due to their key ecological roles and unique biological traits, i.e., their large body size, long lifespan, and enormous home ranges. Although commercial whaling is currently banned, today´s whales are exposed to a variety of other anthropogenic stressors and concomitant ecological impacts, such as climate change, fisheries bycatch, entanglement with fishing gear, wounds from vessel strikes, disease epidemics, alterations in food availability, ingestion of plastics, exposure to toxins, and numerous other stressors. Understanding the effects and identifying the relative importance of multiple stressors is critical for managing endangered species and in this context, methods in conservation physiology can help. Traditionally, physiological and endocrine assessments have used plasma-based analyses. Implementing such techniques to monitoring the physiology of mysticetes (baleen whales) are largely impractical or impossible, so novel approaches have resulted in the adaptation and validation of several physiological analyses, particularly endocrine assays, to quantify analytes of interest from alternative sample types, such as feces, respiratory vapor, blubber samples, baleen, and earplugs. Outputs from these analyses can be used to infer the physiological status of whales. In this dissertation, I validated and applied a novel method in conservation physiology to investigate the potential cause or causes of calf mortalities of southern right whales (SRW, Eubalaena australis) of Península Valdés (PV), Argentina. From the period of 1993-2002 as compared to 2007-2013, the average number of calf mortalities per year increased tenfold (8.2 to 80 mortalities per year). Although the cause for increased and recurrent high calf mortalities at PV is currently unknown, negative interactions with Kelp Gulls (KG, Larus dominicanus) stands out amongst several compelling hypotheses that seek to explain the elevated calf mortalities. In short, KGs in Patagonia have developed a microparasitic behavior which consists in attacking living SRW calves to feed on their skin and blubber. I determined appropriate laboratory sampling parameters (minimum mass of sample and solvent:sample ratio) for hormone extractions from baleen, and then quantified lifetime glucocorticoids (cortisol and corticosterone, GC) and metabolic (triiodothyronine, T3) hormones profiles of post-mortem collected baleen plates to retrospectively assess the role of KG interactions on SRW physiology. Based on T3 results, this study suggests no evidence of malnutrition in whale calves exposed to KG attack. However, the strong positive correlation between extent of wounding and glucocorticoid hormones indicate that heavily wounded calves suffered high levels of physiological stress throughout their short lifespans. Thus, considering the negative effect that chronic elevations in GCs levels might pose to SRW calves’ growth and immune system, KG wounding and harassment may have contributed to the high calf mortality observed at the PV calving ground, in Patagonia Argentina. More broadly, my findings highlight that baleen hormone analysis may be a fruitful method with which to explore the physiological and population impacts of other types of stressors, both natural and anthropogenic.

Item Type: Thesis (Doctoral)
Publisher’s Statement: © Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords: Baleen; Conservation Physiology; Glucocorticoids; Southern Right Whale; Thyroid
Subjects: Q Science > QL Zoology
NAU Depositing Author Academic Status: Student
Department/Unit: Graduate College > Theses and Dissertations
College of the Environment, Forestry, and Natural Sciences > Biological Sciences
Date Deposited: 25 Feb 2022 16:47
Last Modified: 25 Feb 2022 16:47
URI: https://openknowledge.nau.edu/id/eprint/5758

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