Linking Feeding and Reproductive Ecology in Beluga (Delphinapterus leucas) and Narwhal (Monodon monoceros) by Tritsya C. Kelley A Thesis submitted to the Faculty of Graduate Studies of the University of Manitoba in partial fulfillment of the requirements of the degree of Doctor of Philosophy Department of Environment and Geography University of Manitoba Winnipeg, MB © 2014 Abstract Beluga whales (Delphinapterus leucas) and narwhals (Monodon monoceros) are arctic specialists. Both species show philopatry to their summer grounds, though the reason for this site tenacity is not well understood. Aside from migration routes, little is known about other aspects of monodontid ecology, such as their mating and feeding ecology. An understanding of the feeding ecology of a species may provide some insights into their mating ecology, and vice versa. The purpose of this thesis is to relative testes mass and dietary biomarkers to gain insights in the mating and feeding ecology of both species, as well as possible links between the two. Relative testes and brain masses and body masses of odontocetes were collected from the literature and analysed for correlations between sexual size dimorphism (SSD), relative brain mass, and relative testes mass. Results indicate that odontocete species follow a pattern of increasing SSD with decreasing testes mass. An examination of reproductive tracts from belugas and narwhal collected across the Canadian arctic was performed to examine differences in beluga and narwhal mating systems. Belugas were found to have larger relative testes masses, and narwhal testes masses were correlated with tusk length, indicating that sperm competition may play a larger role in the beluga mating system than for narwhal, and narwhal tusks may be honest indicators of male fitness. Investigations of narwhal and beluga feeding ecology using dietary biomarkers were conducted. In the summer, belugas appear to be congregating and feeding in the estuary plume during the summer, as opposed to along ice floe edges in the spring. Spring diets are ii representative of diets consumed during the beluga mating season, and no sexual segregation in carbon isotopes or fatty acids was apparent. There was no evidence for sexual segregation in feeding habits outside the mating season, either. Conversely, narwhal showed some evidence of sexual segregation outside the mating season, and the sexes may be feeding in different food webs. Results suggest that belugas may have a more promiscuous mating system, while narwhals are more polygynous. Implications for conservation for both species are discussed. iii Acknowledgements Thank you to my advisor, Dr. Steven Ferguson, for his support throughout my thesis, as well as his enthusiasm, motivation, and patience, and providing me with the opportunity to conduct research in the Arctic and climb mountains in South Africa. Thank you also to my committee members, Dr. David Walker and Dr. Kevin Campbell, for their insights, suggestions, and guidance. I am thankful to the many researchers, Inuit hunters, and lab partners that I have worked with over the course of my degree, for your invaluable assistance in the lab and in the field. Thank you to the many friends and family members for you encouragement and distractions throughout the years. I am especially grateful to my parents, for their love and support throughout my degrees and for not letting me give up. iv Table of Contents ABSTRACT ............................................................................................................................. II ACKNOWLEDGEMENTS ......................................................................................................... IV TABLE OF CONTENTS ............................................................................................................. V LIST OF FIGURES ................................................................................................................. VIII LIST OF TABLES ...................................................................................................................... X THESIS FORMAT AND CLAIM ................................................................................................. XI 1 GENERAL INTRODUCTION ............................................................................................... 1 1.1 BELUGA AND NARWHAL BIOLOGY .............................................................................................. 1 1.2 CONSERVATION CONCERNS ..................................................................................................... 2 1.3 MATING SYSTEMS AND FEEDING ECOLOGY ................................................................................. 5 1.3.1 Environmental Influences on Mating Systems ............................................................ 6 1.3.2 Seasonality of Mating .................................................................................................. 9 1.3.3 Sexual Segregation .................................................................................................... 10 1.4 ESTIMATING MATING SYSTEM ............................................................................................... 10 1.5 USING DIETARY BIOMARKERS TO UNDERSTAND FEEDING ECOLOGY ............................................... 12 1.6 THESIS APPROACH AND OBJECTIVES ........................................................................................ 13 1.7 REFERENCES ....................................................................................................................... 16 2 LARGE TESTES AND BRAIN MASSES IN ODONTOCETES: THE INFLUENCE OF MATING SYSTEM ON ENCEPHALIZATION ....................................................................... 30 2.1 ABSTRACT .......................................................................................................................... 31 2.2 INTRODUCTION ................................................................................................................... 33 2.3 METHODS .......................................................................................................................... 39 2.3.1 Data Collection ........................................................................................................... 39 2.3.2 Preliminary Analysis .................................................................................................. 40 2.3.3 Phylogenetic Analysis ................................................................................................ 41 2.4 RESULTS ............................................................................................................................ 41 2.4.1 Preliminary Analysis .................................................................................................. 41 2.4.2 Phylogenetic Analysis ................................................................................................ 42 2.5 DISCUSSION ........................................................................................................................ 42 2.6 REFERENCES ....................................................................................................................... 50 3 MATING ECOLOGY OF BELUGA (DELPHINAPTERUS LEUCAS) AND NARWHAL (MONODON MONOCEROS) AS ESTIMATED BY REPRODUCTIVE TRACT METRICS ....................................... 62 3.1 ABSTRACT. ......................................................................................................................... 63 v 3.2 INTRODUCTION ................................................................................................................... 64 3.3 METHODS .......................................................................................................................... 69 3.3.1 Data Collection ........................................................................................................... 69 3.3.2 Reproductive Status ................................................................................................... 72 3.3.3 Mass ............................................................................................................................ 72 3.3.4 Statistical Analysis ..................................................................................................... 73 3.4 RESULTS ............................................................................................................................ 76 3.4.1 Males........................................................................................................................... 76 3.4.2 Females ....................................................................................................................... 80 3.5 DISCUSSION ........................................................................................................................ 81 3.6 REFERENCES ....................................................................................................................... 97 4 STABLE ISOTOPES AND FATTY ACIDS DIFFERENTIATE BETWEEN SUMMER AND SPRING FEEDING IN BELUGAS (DELPHINAPTERUS LEUCAS) IN HUDSON BAY ................................... 109 4.1 ABSTRACT ........................................................................................................................ 110 4.2 INTRODUCTION ................................................................................................................. 112 4.3 METHODS .......................................................................................................................