Low-Frequency Sound and Marine Mammals

Current Knowledge and Research Needs

Committee on Low-Frequency Sound and Marine Mammals Ocean Studies Board

Commission on Geosciences, Environment, and Resources National Research Council

NATIONAL ACADEMY PRESS
Washington, D.C.
1994



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--> Low-Frequency Sound and Marine Mammals Current Knowledge and Research Needs Committee on Low-Frequency Sound and Marine Mammals Ocean Studies Board Commission on Geosciences, Environment, and Resources National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1994

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--> NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competence and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. Support for this project was provided by the U.S. Office of Naval Research Contract No. N00014-92-J-1560/R. Library of Congress Catalog Card No. 93-61700 International Standard Book Number 0-309-05025-1 Additional copies of this report are available from: National Academy Press 2102 Constitution Avenue, NW Box 285 Washington, DC 20055 800-624-6242 202-334-3313 (in the Washington Metropolitan Area) B-267 Copyright 1994 by the National Academy of Sciences. All rights reserved. Printed in the United States of America Cover art by Ellen Hill-Godfrey. Ms. Hill-Godfrey received her Master of Fine Arts degree from the University of North Carolina-Chapel Hill. Her paintings and prints have been exhibited in the Washington, DC, area and throughout the Mid-Atlantic and Southern regions. She has done illustrations for the University of Georgia Press and the University of North Carolina's Endeavors magazine. She lives in Germantown, MD, and teaches at The Barnesville School.

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--> COMMITTEE ON LOW-FREQUENCY SOUND AND MARINE MAMMALS David M. Green, University of Florida, Chairman Harry A. DeFerrari, University of Miami Dennis McFadden, University of Texas John S. Pearse, University of California at Santa Cruz Arthur N. Popper, University of Maryland W. John Richardson, LGL Ltd., King City, Ont., Canada Sam H. Ridgway, Naval Ocean Systems Center at San Diego Peter L.Tyack, Woods Hole Oceanographic Institution Staff Mary Hope Katsouros, Director Robin Peuser, Project Officer LaVoncyé Mallory, Senior Secretary Curtis Taylor, Office Assistant

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--> OCEAN STUDIES BOARD William Merrell, Texas A&M University, Chairman Robert A. Berner, Yale University Donald F. Boesch, University of Maryland Kenneth Brink, Woods Hole Oceanographic Institution Gerald Cann, Independent Consultant Robert Cannon, Stanford University Biliana Cicin-Sain, University of Delaware William Curry, Woods Hole Oceanographic Institution Rana Fine, University of Miami John E. Flipse, Texas A&M University Michael Freilich, Oregon State University Gordon Greve, Amoco Production Company Robert Knox, Scripps Institution of Oceanography Arthur R. M. Nowell, University of Washington Peter Rhines, University of Washington Frank Richter, University of Chicago Brian Rothschild, University of Maryland Thomas Royer, University of Alaska Lynda Shapiro, Oregon State University Sharon Smith, University of Miami Paul Stoffa, University of Texas Liaison Member John Orcutt, Chairman, Navy Committee, Scripps Institution of Oceanography Staff Mary Hope Katsouros, Director Edward R. Urban, Jr., Staff Officer Robin Peuser, Research Associate David Wilmot, Research Associate Mary Pechacek, Administrative Associate LaVoncyé Mallory, Senior Secretary Curtis Taylor, Office Assistant

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--> COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND RESOURCES M. Gordon Wolman, The Johns Hopkins University, Chairman Patrick R. Atkins, Aluminum Company of America Peter S. Eagleson, Massachusetts Institute of Technology Edward A. Frieman, Scripps Institution of Oceanography W. Barclay Kamb, California Institute of Technology Jack E. Oliver, Cornell University Frank L. Parker, Vanderbilt University Raymond A. Price, Queen's University at Kingston Thomas C. Schelling, University of Maryland Larry L. Smarr, University of Illinois at Urbana-Champaign Steven M. Stanley, The Johns Hopkins University Victoria J. Tschinkel, Landers and Parsons Warren Washington, National Center for Atmospheric Research Edith Brown Weiss, Georgetown University Law Center Staff Stephen Rattien, Executive Director Stephen D. Parker, Associate Executive Director Morgan Gopnik, Assistant Executive Director Jeanette Spoon, Administrative Officer Sandi Fitzpatrick, Administrative Associate Robin L. Allen, Senior Project Assistant

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--> The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is the president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. Robert M. White are chairman and vice chairman, respectively, of the National Research Council.

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--> Preface By passage of the Marine Mammal Protection Act (MMPA) of 1972, the United States acknowledged through public policy that marine mammals are a valuable national resource to be protected. Various human activities affect marine mammals and such activities are being discussed as part of the national debate during the reauthorization of the MMPA. A crucial element in the debate is the conflicting demands of protecting and conserving marine mammals versus allowing human activities that are considered important to the nation but that might affect marine mammals. In particular, the issue of whether and how low-frequency sound might affect marine mammals has escalated to national attention because of a proposal to repeatedly measure the speed of sound in the ocean over time to determine if the ocean and the global atmosphere are warming. The Acoustic Thermometry of Ocean Climate (ATOC) project proposes to use low-frequency sound along long-distance undersea paths. This is an important issue because ocean scientists employ low-frequency sound in: geophysics research, to determine the structure of the ocean sediment and crust; ocean acoustic tomography, to study three dimensional structure of the water column over distances from 100-1000 kin; ocean acoustics, to study the acoustical properties of the ocean such as propagation in ocean waves and reflections from the surface and bottom of the sea; and biological oceanography,

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--> to study marine organisms such as populations in the deep scattering layers. In 1992, the National Research Council (NRC) established a Committee on Low-Frequency Sound and Marine Mammals under the auspices of the NRC Ocean Studies Board. The committee was chaired by Dr. David M. Green and included a range of expertise: marine mammal behavior and vocalizations, marine mammal physiology, marine mammal bioacoustics, fish bioacoustics, marine ecology, underwater acoustics, and human hearing. This report is comprehensive and timely, contributing important information relevant to the current debate about the potential effects of low-frequency sound on marine mammals. As the public discussion intensifies, this report serves as an objective review of the current state of knowledge on this subject, recommends changes in the regulatory process to improve acquisition of scientific knowledge (not just about marine mammals but also about the ocean and Earth), and also proposes experiments that should provide the needed information to evaluate the effects of intense low-frequency sounds on a variety of marine mammals and their major prey. WILLIAM J. MERRELL CHAIRMAN, OCEAN STUDIES BOARD

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--> Acknowledgments The committee would like to acknowledge the contributions to the development of this report by several individuals who provided background information, including presentations to the committee, and who participated in several discussions on the topic of the effects of low-frequency sound and marine mammals. The committee would like to express its gratitude to Dr. Whitlow Au, Dr. Aleta Hohn, Dr. Joal Newcomb, Dr. Robert Hofman, Dr. Greg Silber, Dr. Dan Costa, Ms. Carol Fairfield, Dr. Melbourne Briscoe, Dr. Steven Swartz, Dr. Darlene Ketten, Mr. Charles Malme, Dr. Alan Berman, and Mr. Donald Baur for their valuable contributions. In addition, the committee would like to thank Mr. William Schevill, Dr. William Watkins, Ms. Nina Young, and Mr. Bruce McKay for their willingness to meet and discuss this topic with the committee.

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--> Contents     List of Figures and Tables   xiii     Executive Summary   1 1   A Review of Current Knowledge   8     Changes in Ocean Sounds and Potential Effects on Marine Mammals   9     Evaluating Noise Interfence   12     Transmission Loss of Sound in the Ocean   12     Ambient Noise Level of the Sea   13     Acoustic Characteristics of Marine Mammal Hearing Organs   13     The Need for Additional Research   17     Origins and Drawbacks of the ''120-dB Criterion,''   18     References   21 2   Regulatory Barriers and Possible Alternatives   25     The Marine Mammal Protection Act and Its Interpretation   25     Harassment of Marine Mammals   27     Permitting Implications for Research Activity   29     Scientific Research Permits   29     Small Incidental Take (SIT) Authorizations   31

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-->     Magnitude of Potential Noise Pollution from Oceanic Acoustics Studies   33     Proposed Changes in the Regulatory Structure   35     Using a New Mechanism to Regulate Scientific "Takes,"   35     Utilization of the IACUC System   36     Streamlining Existing Regulations   36     Summary of Recommended Changes   38     References   39 3   Topics for Future Research   40     Behavior of Marine Mammals in the Wild   41     Natural, Ecologically Important Signals   42     Habituation to Repeated Human-made Sounds   43     Differential Responses of Migrating Whales to Various Human-made Sounds   45     Responses of Deep-diving Marine Mammals to Low-frequency Sounds   46     Structure and Function of the Auditory System   47     Basic Studies of Audiometry   47     Measurements on Ensnared or Beached Marine Mammals   48     Replication of Data   50     Temporary Threshold Shift   50     Basic Studies of the Anatomy and Physiology of the Auditory System   52     Effects of Low-Frequency Sounds on the Food Chain   53     Development and Application of Measurement Techniques   54     Tag Development   54     Integrated Undersea Surveillance System (IUSS)   56     SWAT Team for Studying Hearing by Ensnared or Beached Animals   57     Warning Signals   57     References   58     Appendixes     A   Comparison of Sound-Pressure Reference Levels in Air and Water   63 B   An Introduction to Marine Mammals   65 C   Comparison of Yearly Sound Energy from Oceanographic Research and Supertankers   74

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--> List of Figures and Tables Figures Figure 1.   Ambient noise spectra   11 Figure 2.   Underwater audiograms of selected toothed whales (A) and pinnipeds (B)   15 Tables Table A-1.   Typical Airborne Sounds and Some Sound Levels of Marine Mammals   64 Table B-1.   Classification of the Living Mammals of the Order Cetacea   67 Table B-2.   Marine Mammals (Pinnipeds, Otters, Polar Bears) of the Order Carnivora   71 Table B-3.   Living and Recent Members of the Totally Aquatic Order Sirenia (Sea Cows)   72

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