VOCAL SOUNDS OF THE CHINCHILLA Heather Hunyady A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 2008 Committee: Ronald Scherer, Advisor Donald Cooper Laura Dilley ii ABSTRACT Ronald Scherer, Advisor Purpose: The goal of this project was to categorize the fundamental frequency and durational patterns of chinchilla (laniger) vocal productions relative to typical interaction situations. Methods: This project focused on 4 distinct call types: Exploratory, Contact, Bark, and Alarm from three sources: doctoral dissertation supplements, pet owner posts, and newly collected samples from a single chinchilla. Praat was used to extract the fundamental frequency (F0) contour from the recordings. Results: Primary characteristics of the Exploratory utterances were: token Fo contours had a rapid decrease in frequency (136 ST/s), (2) token durations and token periods overlapped to a large extent across animals, 77% of all tokens contained a final Fo up-sweep tag, and utterances contained an average of 9 tokens. The Contact utterances contained 2-4 Exploratory-like tokens preceding a few transitional tokens, segueing into a sequence of the Contact tokens, Fo contours were complex, variable, and low pitched (300-800 Hz), there is a typical brief “low Fo dip” of less than an octave from the preceding and following Fo, and the utterances contained an average of approximately 7. Bark utterances were characterized by a brief tonal segment followed by a distinctive noise interval, an abrupt intensity onset followed by a more gradual intensity offset, an increase in token period duration across the utterance, an intensity decrease across the tokens, with a variant of the Bark category including an inspiratory tone preceding or following the token, and the utterances contained an average of 6 tokens. iii The Alarm utterance token was a high intensity call that included a large, very rapid frequency jump, and maintained a high intensity throughout. iv ACKNOWLEDGMENTS I would like to sincerely thank Dr. Ronald Scherer, project advisor for his guidance and continued optimistic support. I would like to thank committee members, Dr. Laura Dilley and Dr. Donald Cooper, for your patience, encouragement, and advice. Additionally, I would like to acknowledge Lynn Hewitt, Larry Small, and the Communication Disorders Department. v TABLE OF CONTENTS Page INTRODUCTION ................................................................................................................. 1 Animal Communication............................................................................................. 1 History of the Chinchilla............................................................................................ 2 Behavior of the Chinchilla......................................................................................... 4 Anatomy and Physiology of the Chinchilla............................................................... 6 Hearing, Vision, and Smell............................................................................ 6 Respiration ..................................................................................................... 7 Dentition and Tongue.................................................................................... 7 Vocal Tract..................................................................................................... 7 Larynx ............................................................................................................ 8 Reproduction.................................................................................................. 9 Body Composition ......................................................................................... 10 Habitat of the Chinchilla............................................................................................ 11 LITERATURE REVIEW ...................................................................................................... 14 Chinchilla Vocal Communication.............................................................................. 14 Work by Susan Carol Vogt (1980) ................................................................ 14 Work by Juliana Bartl (2006.......................................................................... 17 World Wide Web Sources, Ross (2006) and Termathe (2006) ..................... 22 Summary ............................................................................................................ 23 METHODS ........................................................................................................................... 24 Observational Contexts ............................................................................................. 24 vi New Recording (“Chester”)....................................................................................... 25 Acquisition of Fundamental Frequency and Intensity............................................... 25 Accuracy of F0 Recording and Analysis ................................................................... 26 Analysis of Fundamental Frequency and Intensity.................................................... 32 RESULTS ........................................................................................................................ 35 Exploratory Call......................................................................................................... 36 Contact Call............................................................................................................... 41 Bark Call.................................................................................................................... 43 Alarm Call.................................................................................................................. 46 DISCUSSION ........................................................................................................................ 50 General Findings........................................................................................................ 50 Comparison to Vogt (1980) ....................................................................................... 53 Comparison to Bartl (2006) ....................................................................................... 54 Comparison to Other Mammals................................................................................. 54 CONCLUSIONS.................................................................................................................... 56 REFERENCES ...................................................................................................................... 58 APPENDIX............................................................................................................................ 61 vii LIST OF TABLES Table Page 1 Chinchilla taxonomy.................................................................................................. 4 2 Observational description of chinchilla vocalizations ............................................... 6 3 Physical distinctions between chinchilla langier and chinchilla brevicaudata .......... 11 4 Physical properties of the “ow unit” .......................................................................... 16 5 Frequency characteristic of prototypical “hoot units” ............................................... 17 6 Corpus, source, and quantity of wav file recordings ................................................. 21 7 Olympus-based Fo vs. Windaq-based Fo – correlation between values, average Fo difference between values, and standard deviations of the Fo differences................ 31 8 Vocalization sample labels broken down by source and call category...................... 35 9 Exploratory call measures.......................................................................................... 38 10 Exploratory up-sweep tag frequency and amount of token involved in the up-sweep tag 39 11 Summary of vocal production categories in relation to communication context, token corpus, and token similarity....................................................................................... 50 viii LIST OF FIGURES Figure Page 1 Typical chinchilla laniger skull.................................................................................. 8 2 Microscopic view of the larynx of chinchilla laniger ................................................ 9 3 Photograph of a Chinchilla Laniger, (“Chester”). ..................................................... 12 4 “Positionslaute”, spectrogram of exploratory vocalization series ............................. 19 5 “Lockruf”, wave form and spectrogram of a contact vocalization series.................. 20 6 “Alarmruf”, waveform and spectrogram of an offensive bark series ........................ 20 7 “Schrei”, waveform and spectrogram of an alarm call ............................................. 21 8 The total range of Fo should cover the range produced by Chester 8a. Fo sweeps from Olympus recorder ...................................................................... 28 8b. Fo sweeps from Dataq recorder ........................................................................... 28 9 Fo comparisons between Windaq-based and Olympus recorder-based recordings for four female Fo sweeps and four whistle sweeps. ............................................................. 30 10 Token duration measures: token duration, token period,