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Ann Arbor,MI 48106 ACOUSTIC AND VISUAL TRACKING REVEALS DISTRIBUTION, SONG VARIABILITY AND SOCIAL ROLES OF HUMPBACK WHALES IN HAWAIIAN WATERS A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAII IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN OCEANOGRAPHY DECEMBER 1994 By Adam S. Frankel Dissertation Committee: Louis M. Herman, Chairperson Alexander Malahoff Craig R. Smith Dixon Stroup Joseph R. Mobley, Jr. © Copyright 1994 by Adam S. Frankel All Rights Reserved iii This dissertation is dedicated to my parents, Patricia M. Frankel and Alan Arby Frankel, Ph.D.. I wish that he were here to see the next Dr. Frankel. iv Acknowledgments As in all dissertations, there are numerous people to thank. In my case, they come from a wide geographic range. The person most deserving mention is Christopher W. Clark, without whose help this dissertation would not have been possible. The people involved with the field work in Hawai'i include Gordon Bauer, C. Scott Baker, Tom Freeman, Anjanette Perry, Brooks G. Bays, Frank Minogue, David Helweg, Michael A. Hoffhines, Christine M. Gabriele, Yin, and Hilary L. Maybaum. Those in Hawai'i who have contributed in their own way include Shannon Atkinson, Shawn Doan, Craig Moyer, Ed Laws, Ed Parnell, Sheryl McCarthy, Christoph Heironymus, Colleen Allen, Stewart Reid, John Constinou, Chuck Holloway and Monika Fischer. People at Cornell University who have contributed include Kathy Breese, Jenn Colby, Janet Doherty, Sean Cunningham, Brian Corzillius, John Bower, Steve Mitchell, Tom Calupca, Dave Mellinger, Russ Charif, Katy Payne, Susie Minges, Matt Irinaga, Mia Griafalconi, Craig George and the North Slope Borough, Katy Payne and Connie Gordon. The North Slope Borough also provided much needed equipment. This work has been supported by UH Sea Grant, Waikoloa Marine Life Fund, American Museum of Natural History, Earthwatch and the Cornell Bioacoustics Research Program. v Abstract Acoustic and visual methods were used to track and observe humpback whales off Hawai'i. Chapter 3 found 62 singing whales were located acoustically in water depths from 10 to 305 fathoms. This indicates that singers are not confined within the 100 fathom contour, although near shore waters had a higher density of singers. The relative bearings from one singer to another indicated that singers predominantly oriented and moved away from other singers. A negative relationship was found between change-in-separation and the initial distance between singers, thus singers close to another were more likely to increase their separation. These observations suggest that 4 km is the preferred minimum spacing between singers off Northwestern Hawai'i. Some singers actively swam while singing and others continued singing while afftliating with or being joined by other whales. The correlation between breaching and the cessation of singing suggests that the sounds of aerial behavior can convey information to other whales. Humpback whales song has been characterized as having the same structure shared by all individuals simultaneously. Chapter 4 found that the songs ofindividual whales were significantly different from one another at the level of the song unit. Significant differences were found in the duration, bandwidth, lowest frequency, frequency of peak amplitude and the source level ofdifferent singers. The implication of these findings is that these small scale differences allow for the possibility ofassessment of the song and the singer by other animals. The opposite end of the acoustic sensory modality was examined in Chapter 5. Whales responded to playbacks of biological and synthetic sounds. An empirically determined measurement ofsound transmission loss allowed the received sound levels to be estimated when the stimulus was presented. The lowest sound level that produced a response was 102 dB re I f.J.Pa. This corresponds to a 16 dB signal-to-noise ratio. This vi value is probably an underestimate of the response threshold and certainly an underestimate of their hearing threshold. Taken together, these findings reported here suggest the need to expand the traditional interpretations of singing humpback whales as obtained from visual observations alone. vii Table of Contents Acknowledgments v Abstract. vi List of Tables .ix List of Figures x List of Abbreviations xi Chapter I: Introduction 1 Chapter 2: General Methods for Data Collection 24 Chapter 3: Habitat Utilization and Social Interactions 39 Chapter 4: Variation in Structure and Amplitude of Humpback Whale Song Units 59 Chapter 5: Behavioral Response Thresholds to Playback of Biological Signals 89 Chapter 6: Summary and Synthesis 107 Appendix I: Behavioral Ethogram 122 Appendix 2: Sonogram Parameters 126 Literature Cited 128 Vlll List of Tables Table Page 2.1 Non-Focal Ethogram 38 3.1 Relative Singer Bearings .46 4.1 Repeated Measures Omnibus Tests 72 4.2 Summary of Univariate Song Feature Tests 73 4.3 F-scores, Degrees of Freedom and Probabilities for Univariate Tests 87 5.1 Sound Conditions used during Playback Experiments 92 5.2 Calculated Received Levels for Playback Trials that Resulted in Rapid Approach Responses: Biological and Synthetic Sounds 102 6.1 Model of Male Strategies 119 IX List of Figures Figure Page 2.1 Study Area 25 2.2 Diagram of Sonobuoy Mooring Rig 30 2.3 Intersection of Three Hyperbolic Pointing Lines 34 3.1 Mean Location of Singers .43 3.2 Inter-Individual Spacing .45 3.3 Four Simultaneously Moving Singers .48 3.4 An Affiliation of a Singer with Another Whale .49 3.5 A Whale Approaches and Affiliates with a Singer 51 4.1 Spectrogram of Theme 2 65 4.2 Spectrogram of Theme 3 66 4.3 Spectrogram of Theme 4 67 4.4 Theme 2 Unit 1 Measures 74 4.5 Theme 2 Unit 2 Measures 75 4.6 Theme 3 Unit 1 Measures 76 4.7 Theme 3 Unit 2 Measures.....................................................77 4.8 Theme 4 Unit 1 Measures.....................................................78 4.9 Theme 4 Unit 2 Measures.....................................................79 4.10 Source Level v. Range 81 5.1 Kawaihae Bay Transmission Loss 96 5.2 Whale-Vessel Separation 98 5.3 Whale Speed 100 5.4 Distributionof Rapid Approach Responses by Received Level... 101 x List of Abbreviations Abbreviation Full Spelling Description dB Decibel A measure of sound pressure ~a microPascal A reference sound pressure level Hz Hertz A measure of sound frequency dB re 1~a2/Hz Decibel referenced to A measure of sound pressure in 1 micropascal squared per a 1 Hertz wide frequency band hertz xi xii Chapter 1 Introduction OVERVIEW Life is divided into two components: Survival and reproduction. It can be argued that every purposeful act ofan animal directly or indirectly serves these goals. The migratory nature of humpback whales provides a unique opportunity to study these components, since mating and feeding appear to be both spatially and temporally separated by migration (Baker and Herman, 1984b). Humpback whales (Megaptera novaeangliae) feed primarily during the summer, in the highly productive northern end of their range (Jurasz and Jurasz, 1979). Humpbacks subsist upon their energy reserves stored in the blubber while migrating and on the wintering grounds (Slijper, 1962; Brodie, 1975; Lockyer, 1981). The biology and behavior of humpback whales during the winter in the low latitudes is dominated by reproduction (Chittleborough, 1965; Dawbin, 1966). Females return to the wintering ground either with or without a calf, and both of these classes mayor may not mate that year. The average interval between calving years is between 2.4 and 2.8 years (Baker et aI., 1987; Clapham and Mayo, 1987). There is considerable variation in this interval; the inter-calf interval can range from 0 to 9 years (Baker et al., 1987; Glockner-Ferrari and Ferrari, 1990). During the winter, male humpbacks exhibit two modes of social behavior. The first is active physical competition between males for reproductive access to females (Tyack and Whitehead, 1983; Baker and Herman, 1984a; Clapham et aI., 1992; Medrano et al., in press). The second is the singing behavior of males (Payne and McVay, 1971; Winn and Winn, 1978). Song appears to be a reproductive display, although its exact function remains unknown.