VOCAL BEHAVIOR OF CAPTIVE ATLANTIC BOTTLENOSE DOLPHINS IN A SWIM PROGRAM by Deborah D. Boege A Thesis Submitted to the Faculty of The College of Science in Partial Fulfillment of the Requirements for the Degree of Master of Science Florida Atlantic University Boca Raton, Florida April 1994 For My Father, Harald, In Loving Memory VOCAL BEHAVIOR OF CAPTIVE A1LANTIC BOITLENOSE DOLPHINS IN A SWIM PROORAM by Deborah D. Boege This thesis was prepared under the direction of the candidate's thesis advisor, Dr. Godfrey R. Bourne, Department of Biological Sciences and has been approved by the members of her supervisory committee. It was submitted to the faculty of the College of Science and was accepted in partial fulfillment of the requirements for the degree of Master of Science. SUPERVISORY COMMITIEE: Chairman Dr. Daniel F. Austin ~u_ ~~ Dr. Michael Salmon Date ii ACKNOWLEDGEMENTS I thank Drs. Daniel F. Austin, Godfrey R. Bourne, and Michael Salmon for providing helpful comments about experimental design, and on early drafts of the thesis. I am particularly grateful to G. R. Bourne for his continuous support and invaluable advice throughout this project. The generous permission to conduct this research was granted by Lloyd and Rick Borguss of Dolphins Plus to whom I am greatly indebted. I appreciate the staff of Dolphins Plus, particularly Wendy Kellam, for their cooperation and hospitality. I also thank Scott Spitz for all his help, and Annika Woehr for fieldwork assistance. Special gratitude is owed to Judy Hicklin and Sue Schmidt for their statistical advice and assistance when Dr. Bourne was out of the country. Finally, I especially thank Ingeburg Boege and Michael Schmidt for their continuous encouragement and enthusiastic support. A Marine Biology Research Grant through the Department of Biological Sciences, Florida Atlantic University, equipment loans from G. R. Bourne, Ed Gerstein, and M. Salmon, and contributions from Joe Scandroli, Judy Fuchs, and the Spitz family made it possible for me to conduct this research. ill ABSTRACT Author: Deborah D. Boege Title: Vocal Behavior of Captive Atlantic Bottlenose Dolphins in a Swim Program Institution: Florida Atlantic University Thesis Advisor: Dr. Godfrey R. Bourne Degree: Master of Science Year: 1994 Dolphins emit distinct vocalizations in the contexts of stressful situations, such as when captured in nets. It has been assumed among animal rights groups that the presence of human swimmers causes stress in captive Atlantic bottlenose dolphins (Tursiops truncatus). Stress may be expressed in dolphin vocalizations and the associated visual behaviors before, during, and after swim sessions with humans. Thus, these behaviors were recorded to elucidate quantitative vocal patterns suggestive of conspecific stress. Significant differences among vocalization types within sample sessions were found only for whistles between During II and After sessions. Other comparisons indicated no significant differences for vocalization production frequencies between the presence or absence of human swimmers. Additionally, correlations found among the seven vocalization types and all five sample sessions indicated only that one variable, i.e. the presence or absence of human swimmers, was being measured in several different ways (by the different vocalization type production frequencies). Thus, conspecific stress, if indeed it can be measured by vocalization production frequency, does not appear to occur more often in the presence of human swimmers. IV TABLE OF CONTENTS ACKNOWLEDGEMENTS ........................................................................ iii ABSTRACT .......................................................................................... iv LIST OF TABLES .................................................................................. vi LIST OF FIGURES ................................................................................ vii INTRODUCTION ................................................................................... 1 MATERIALS AND METHODS ................................................................... 3 Study Site and Animals ..................................................................... 3 Recording Procedures ...................................................................... 3 Vocalization Categories ..................................................................... 4 Behavioral Categories ...................................................................... 5 Statistical Analyses .......................................................................... 6 RESULTS ............................................................................................. ? Vocalizations ................................................................................. 7 Vocal Behavior. .............................................................................. 7 DISCUSSION ...................................................................................... 15 Sample Sessions and Vocal Behavior ................................................... 15 Conclusions .............. .................................................................. 16 LITERATURE CITED ............................................................................. 18 v LIST OFTABLES 1. Vocalization parameters used to distinguish between vocalization types (N = 70) ........................ .. ......... ................. .................. 9 2. Mean numbers and standard errors of vocalization totals by session (N = 276) .......... .................. ... ...... ................................ 11 3. Results of analysis of variance for seven vocalization types among five sample sessions employing square root transformed data [DF = 4 (session types), 271 (sessions); N = 276 (total number of sessions sampled)] ................................................ 12 4. Matrix of significant differences (P values) among pairwise sample session comparisons within each vocalization type at Dolphins Plus estimated using a one-way ANOV A model, after square root transformations, followed with pairwise post-hoc Fisher's Protected LSD tests (Nscss ion s = 276) ................................... 13 VI LIST OF FIGURES 1. Audiospectrograms and waveforms of dolphin vocalization types ......................... 8 2 . Frequencies of seven audible behavior types emitted by dolphins during the five sample sessions ................................................................ lO Vll INTRODUCTION Many cetaceans, including Atlantic bottlenose dolphins (Tursiops truncatus Montagu), exhibit highly developed auditory and sound producing systems, and are among the most vocal of the nonhuman mammals (Herman and Tavolga, 1980). Little is known about the social contexts in which captive and free-living dolphins vocalize (Herman and Tavolga, 1980; Herman, 1991; Tyack, 1991). However, Caldwell and Caldwell (1965) contend that bottlenose dolphins might emit more, louder, and faster whistles when stressed. Some sounds produced by dolphins are coordinated with a visible display. For example, the jaw clap is a sound produced by the snapping together of the jaws, and is usually emitted in conjunction with an agonistic, open mouth display (Wood 1954). Moreover, according to Caldwell et a!. (1962), Pryor (1973), Norris and Dohl (1980), Ralston and Herman (1989), and Pryor and Schallenberger (1991) certain visual displays, such as tail slaps, jaw claps, and tail swishes, as well as high-energy vocalizations, including repetitive whistling bouts, and rapid burst-pulse sounds (referred to as "barks" in this study) appear to be indications of agitation and stress among both captive and wild dolphins. There is concern among animal rights groups that stress may be induced in captive dolphins by the presence of human swimmers that are without escape routes (DeGeorge, 1989; Linden, 1989). Only two studies (Ostman, 1991; Spitz, 1993) have quantitatively analyzed the social behavior of captive dolphins in association with humans. To study the impact human presence has upon captive dolphins, the frequencies of vocalizations, their social contexts, and the associated visual behaviors in which these vocalizations are produced must be examined. An evaluation of auditory emissions is of vital importance in the study of dolphin social behavior. Dolphins have remarkable auditory information processing skills and apparently communicate most often by auditory means (Herman, 1991). Many dolphins are able to detect signals above 100 kHz, thereby suggesting a very specialized hearing apparatus (Schevill and Lawrence, 1952; Popper, 1980; Norris, 1991). The reliance on the auditory rather than the visual system is not surprising, given the short visibility of light in the murky water where some dolphins live. In contrast, nonhuman primates tend to be more visually oriented (D 'Amato, 1973; D 'Amato and Colombo, 1986). Presently there are four Swim-with-the-Dolphins (SWTD) programs in the United States. Each SWTD program is authorized by the Marine Mammal Commission on a "probationary basis" due to the assumption that "undesirable modifications of the dolphin's behavior," including stress and agitation, may result as a consequence of swimming with humans. An examination of vocalizations, with special reference to agonistic emissions, the behavioral contexts in which vocalizations are produced, and the presence or absence of human swimmers may aid in determining whether swimming with humans causes adverse effects on captive dolphins. In this