Contributions from the Mote Marine Laboratory Volume 1, Number 2 Shark Attack: A Program of Data Reduction and Analysis H. David Baldridge Sarasota, Florida 1974 ANNOUNCEMENT The Mote Marine Laboratory is an outgrowth of the Cape Haze Marine Laboratory founded in 1955 by William H. and Alfred G. Vanderbilt and ably directed by Dr. Eugenie Clark from 1955 to 1966. In 1961 the Cape Haze Marine Laboratory was moved from its original location in Placida, Florida to Sarasota, Florida and in 1967 its name was changed to honor its President, William R. Mote. The Mote Marine Laboratory is an independent, nonprofit institution, staffed by resident scientists and visiting investigators. Major areas of interest include continuing programs in Neurobiology and Behavior, Biomedical Studies, Estuarine Ecology, Microbiology and Environ­ mental Health, and the Biology of Elasmobranch Fishes. Volume 1, Number 2 of Contributions from the Mote Marine Laboratory represents the second of a series based on work entirely or chiefly undertaken at this laboratory. Number 1 of the series appeared in 1972 and the mono­ graph entitled "On the relationship of teleost scales to pigment patterns" was authored by Dr. C. M. Breder, Jr. It is with pleasure that we continue the high standards of excellence Dr. Breder's monograph set for the series and publish "Shark attack: A program of data reduction and analysis" by Dr. H. David Baldridge, Senior Research Associate at MML. The publication of the second number in this series is made possible by a generous financial contribution from Elizabeth Mote Rose of Tampa, Florida and from funds provided in Contract N00014-73-C-0252 between the Mote Marine Laboratory and the Office of Naval Research, United States Navy. PERRY W. GILBERT, PHD Director Sarasota, Florida January, 1974 CONTRIBUTIONS FROM THE MOTE MARINE LABORATORY Volume 1, Number 2 Shark Attack: A Program of Data Reduction and Analysis H. David Baldridge Sarasota, Florida 1974 Additional copies may be obtained from MOTE MARINE LABORATORY 9501 Blind Pass Road Sarasota, Florida 33581 $4.00 postpaid Publication costs were partially defrayed by the Office of Naval Research, Department of the Navy, under Contract NOOOI4-73-C-0252 (NR 104-148). PRINTED IN U .S.A. BY ALLEN PRESS, INC., LAWRENCE, KANSAS 66044 ABSTRACT Data from 1165 case histories of shark attack against man were reduced to a form handleable by automatic data retrieval systems. Numerous probes by computer were made to (a) provide statistical significance to the existence or absence of common factors associated with known instances of predaceous shark behavior, and (b) evaluate the present approach to gathering meaning­ ful data on shark attack and thereby determine requirements for maintaining such an effort in the future. Although information was carefully screened for correlations between occurrence of shark attack and a number of environ­ mental and behavioral parameters, it was considered of greater importance that patterns or relationships be identified that distinguished victims from non-victims among exposed populations. Points of interest were examined in the light of previously accepted correlations and popular beliefs. Wound characteristics and other considerations suggested that perhaps 50-75% of shark attacks on humans have no direct relationship to feeding. A number of popular concepts linking shark attack to environmental parameters, in­ cluding water temperature, appear to be casual relationships having to do more with determining bathing pressure at beaches. Contrary to current ideas, divers appear attack prone, with a strong relationship to spearfishing. Trends indicate that, in the 1970's, attacks upon divers will average at least one-third of all reported cases. Yet, divers show fewer, less damaging injuries than swimmers and enjoy a far lower mortality rate. Effectiveness of a variety of weapons and diversionary actions were examined. Updated advisories were developed for bathers and swimmers, divers, and attack victims. The question of shark motivation in human attack was examined. A case was made strongly favoring continuation and expansion of the Shark Attack File. CONTENTS BACKGROUND 1 DEVELOPMENT OF DATA REDUCTION PROCEDURES 2 DATA ASSIMILATION PROGRAM . 5 PRELIMINARY COMPUTER PROGRAMS 6 RESULTS REFLECTING UPON DATA CREDIBILITY 6 Documentation lag time 7 Primary data source 7 Analytical approach 7 DATE AND TIME . 8 Trends in mortality rates 8 Human population dynamics 10 Day of the week . 10 Time of day. 10 Shark population dynamics 11 Conclusions regarding time factors 11 GEOGRAPHICAL CONSIDERATIONS 11 METEROLOGICAL AND HYDROGRAPHIC FACTORS 13 Sunlight conditions . 13 General weather conditions 13 Underwater visibility 14 Sea conditions 14 TEMPERATURES OF AIR AND WATER 14 Water temperature . 14 Feeding behavior of sharks versus temperature 17 Human physiology temperature considerations 18 Conclusions regarding water temperature. 19 Water temperature affecting species of attackers 20 FEATURES OF THE SITE OF ATTACK 21 Proximity to deep water . 21 Depth of water at attack site 23 Relative water depth . 24 Distance from shore . 26 Depth of victim in water at time of attack 28 GENERAL CHARACTERISTICS OF VICTIMS 29 Race ........ 29 VII CON TEN T S (Continued) Sex of victims 30 Age of victims 31 Physical condition of victims prior to attack 31 Skin pigmentation 32 Degree of clothing . 32 Wetsuits . 33 Colors of clothing and gear 34 Laboratory studies on color effects under attack conditions 35 Strikes directed at colored bathing suits . 37 Conclusions regarding importance of color 37 Sudden presentation of unfamiliar color 37 Patterns and special features of clothing 38 General visual presentation . 38 PRESENCES OF POSSIBLE SIGNIFICANCE AT A ITACK SITE 39 Artificial lighting . 39 Animals. 39 Porpoises (dolphins) 39 Other people . 40 Fish. 41 Large floating objects 41 Blood, human 42 Blood, fish . 42 Human waste 43 Garbage or refuse 43 Other chemical stimuli 44 ACTIVITIES OF VICTIMS AND OTHERS IMMEDIATELY PRIOR TO ATTACK 44 Fishing . 44 Provocative acts 46 Specialized gear 46 General activities of others than victims 46 Pre-attack shark behavior . 47 Pre-attack activities of victims . 48 Length of time victim was in water prior to attack 51 Headings of victims in water 51 THEATTACK. 52 Number of sharks directly involved 52 viii CON TEN T S (Continued) Direction of original strike received by victim 53 Nature of initial strike . 53 Aggressive close passes without contact 53 Number of strikes by shark. 53 Number of bites or wound-groups 54 Attacks as single-event encounters 54 Shark behavior during attack . 55 High mortality rate of victims of frenzied sharks 55 Use of weapons against attacking sharks . 55 Chemical and physical anti-shark devices 56 Shark billy . 57 Spears, spearguns, etc. 57 Powerhead or bangstick 57 Diversionary actions by victims and others 57 OUTCOME OF A ITACK 59 Mortality rate . 60 Injury to rescuers 60 Injury to others than primary victims and rescuers 61 Wound characteristics 62 Recovery of tooth fragments from wounds 62 Body parts injured 62 Nature of wounds 64 A ITACKER SHARKS 65 Identity of attackers 65 Basis for identification of attacker sharks 65 Lengths of attacker sharks . 65 Basis for length assignments . 69 Evaluation of abilities to estimate shark length 70 Post-attack shark behavior . 71 Capture of attacker shark . 71 Human remains in sharks' stomachs 71 DIVERS AS VICTIMS OF SHARK A ITACK 72 Trends with time . 72 Distance from shore 73 Depths at which attacks occurred on divers 74 Provocation by divers 74 General activities of divers . 75 ix CON TEN T S (Continued) Direction of initial strike against divers 75 Close passes, strikes, and bites . 75 Body parts injured . 76 Nature of wounds received by divers 77 Mortality rate among diver-victims 78 Lengths of sharks attacking divers 78 Pre-attack shark behavior . 79 Nature of initial strike . 80 Shark behavior during attacks on divers 80 Post-attack shark behavior 81 Identity of sharks . 81 Water temperature . 81 Rescuers of diver-victims 82 Frequent availability of speargun as weapon 82 Summary of observations on attacks involving divers 82 CONCLUSIONS AND RECOMMEND A TIONS 83 Advice to bathers and swimmers 84 Advice to divers . 85 Advice to victims . 86 THE QUESTION OF SHARK MOTIVATION 86 REMARKS CONCERNING STATISTICAL TREATMENTS 90 THE CASE FOR CONTINUING AND EXPANDING THE SAP 91 ACKNOWLEDGMENTS 92 LITERATURE CITED . 93 APPENDIX. Summary listing of localities of 1165 shark attacks for which data were coded and analyzed . 96 x Shark Attack: A Program of Data Reduction and Analysis H. DAVID BALDRIDGE Mote Marine Laboratory BACKGROUND This program had its beginnings along with that of the Shark Research Panel of the American Institute of Biological Sciences (AIBS), which was established on 25 June 1958 by the Office of Naval Research (Gilbert, 1963a). Dr. Sydney Galler, who then headed the Biology Branch of ONR, assembled in April of that year in New Orleans, Louisiana a group of 34 scientists internationally recognized for their knowledge of sharks. The pur­ pose of the conference, which was jointly supported by ONR and the Navy's Bureau of Aeronautics, was to consider basic research approaches to the development of better means for protecting naval personnel from predaceous shark activity. It was generally agreed that to accomplish this goal a much better understanding of the shark attack problem would have to be gained through intensified basic research in such areas as shark behavior, taxonomy, and functional anatomy. The Shark Research Panel was then charged with responsibility to the Navy for serving as a clearing house for information related to elasmobranch biology in general and the shark hazard problem in particular. It would also coordinate Navy-supported research in these and related areas, acting through the Hydrobiology Committee of the AIBS. Dr. Perry Gilbert, present Director of the Mote Marine Laboratory, was chairman of the Panel during its almost 12 years of existence. Other members were Dr. Sydney Galler (ONR), Dr.