Date of Award
Doctor of Philosophy in Biological and Environmental Sciences
Integrative and Evolutionary Biology (IEB)
Becky L. Sartini
With conservation and ethical concerns facing cetaceans, minimally invasive research on reproduction is important for population management. Belugas (Delphinapterus leucas) are endangered in parts of their range, yet little is known about their breeding behavior and much of the existing research depends on post-mortem sampling. To date, there have been no directed studies of social interactions between belugas during the breeding season, and few studies have attempted to correlate reproductive physiology with behavior in any species of cetacean. Improved understanding of reproductive strategies in this species would facilitate management. This work describes the development of minimally invasive methods for determining sex, maturity, and reproductive cycle stage in belugas, and the utilization of these methods to assess relationships between reproductive physiology and behavior in a social group of belugas in an aquarium. The results of this work are interpreted in the context of the current understanding of beluga reproductive physiology and ecology.
Chapter 1 describes the physiological validation of blow (exhale) sampling for measuring testosterone and progesterone in belugas. Concentrations of both progesterone and testosterone in blow are correlated with circulating concentrations and reflect variation in the reproductive status of individuals.
Chapter 2 presents the development of DNA isolation from beluga blow samples and determines the relationship between various sample characteristics and DNA yield and performance in polymerase chain reactions (PCR). Although yield and quality varied greatly among samples, single exhale samples from wild and aquarium belugas enabled PCR amplification of genes used in sex determination or population genetics.
Chapter 3 describes the seasonal variation in testicular volume and testosterone in male belugas studied longitudinally. This work revealed a seasonal increase in testes size in belugas of approximately 50%, filling a significant gap in knowledge for wild belugas.
Chapter 4 utilizes methods developed and validated in Chapters 1 and 3 to evaluate social behavior in a group of aquarium belugas in the context of reproductive physiology. Reproductive seasonality and the occurrence of reproductive events were detected using non-invasive techniques and used to contextualize patterns of association and the frequency of social behaviors of interest, including courtship.
Appendix 1 presents a general review of the literature regarding beluga mating strategies and reproductive biology; specific literature reviews are included with each chapter. Appendix 2 provides a synthesis of the dissertation and discusses the implications of these findings on the current understanding of beluga mating strategies, and by extension, the management and conservation of this species. Appendix 3 presents laboratory protocols utilized in this dissertation, and provides supplementary data that was not included in Chapter 1.
Richard, Justin Thomas, "Correlating Behavior with Non-Invasive Physiological Measures to Evaluate Mating Strategies in Belugas" (2016). Open Access Dissertations. Paper 456.