Distribution, Habitat Use, and Behaviour of Cetaceans in the Greater Dyer Island Area, Western Cape, South Africa
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Distribution, habitat use, and behaviour of cetaceans in the Greater Dyer Island Area, Western Cape, South Africa BY KATJA VINDING PETERSEN Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Zoolog) In the Faculty of Natural and Agricultural Sciences, Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria © University of Pretoria © University of Pretoria June 2016 Supervisor Doctor Simon Elwen Co-supervisor Professor Marthán Bester I, Katja Vinding Petersen declare that the thesis/dissertation, which I hereby submit for the degree Doctor of Philosophy at the University of Pretoria, is my own work and has not previously been submitted by me for a degree at this or any other tertiary institution. 21. June 2016 © University of Pretoria Table of contents SUMMARY 7 3 CETACEAN DATA COLLECTION FROM COMMERCIAL FOREWORD AND ACKNOWLEDGEMENTS 11 WHALE WATCHING VEssELS: CONSISTENCY, VALIDITY, LIST OF FUNDING SOURCES 16 AND VALUE IN LOCAL HABITAT MONITORING 83 ABBREVIATIONS 17 3.1 Abstract 83 3.2 Key words 83 1 GENERAL INTRODUCTION 19 3.3 Introduction 84 1.1 Cetaceans 19 3.4 Materials and methods 85 1.2 Aim and motivation of the study 20 3.4.1 Study area 85 1.3 Research area 21 3.4.2 Data 86 1.3.1 Greater Dyer Island Area 21 3.4.3 Data analysis 86 1.3.2 Potential human impacts 23 3.5 Results 92 1.3.3 Protection status 25 3.5.1 Consistency 92 1.4 Research design and methods 28 3.5.2 Validity 94 1.4.1 Platforms of opportunity (Whale watching) 28 3.6 Discussion 97 1.4.2 Land-based observations (Theodolite tracking) 28 3.6.2 Effort 100 1.4.3 Passive Acoustic Monitoring 31 3.6.3 Observer skills and training 100 1.5 Coastal cetacean species 34 3.6.4 Platform of opportunity or random 1.5.1 Right whales 34 pointless observations? 101 1.5.2 Humpback whales 37 3.6.5 World-wide guidelines 102 1.5.3 Bryde’s whales 38 3.7 Conclusion 103 1.5.4 Indian Ocean humpback dolphins 38 3.8 Literature 104 1.5.5 Indo-Pacific bottlenose dolphins 40 1.6 Organisation of the report 40 4 SHORE-BASED OBSERVATIONS OF FIVE CETACEAN 1.7 Literature 42 SPECIES IN THE GREATER DYER ISLAND AREA, SOUTH AFRICA: SPATIAL DISTRIBUTION, 2 THE USE OF DATA FROM A PLATFORM OF OPPORTUNITY SEASONALITY, AND GROUP COMPOSITION 107 (WHALE WATCHING) TO STUDY COASTAL CETACEANS 4.1 Abstract 107 ON THE SOUTH WEST COAST OF SOUTH AFRICA 53 4.2 Key words 108 2.1 Abstract 53 4.3 Introduction 108 2.2 Key words 53 4.4 Methods 109 2.3 Introduction 53 4.4.1 Study site 109 2.4 The study 55 4.4.2 Shore-based stations 110 2.4.1 Study area 55 4.5 Data collection 112 2.4.2 Data collection and validation 56 4.5.1 Shore-based stations 112 2.4.3 Data analysis 58 4.5.2 Data collection protocols 113 2.5 Results 59 4.5.3 Environmental data and sighting conditions 114 2.5.1 Search effort 59 4.5.4 Distribution scan 114 2.5.2 Cetacean occurrence and seasonal distribution 60 4.5.5 Focal follows or search mode 114 2.5.3 Temporal patterns 62 4.5.6 Surface behaviour in whales 117 2.5.4 Spatial patterns 66 4.5.7 Surface behaviour in dolphins 117 2.5.5 Observed on rare occasions 70 4.6 Analysis 117 2.6 Discussion 71 4.6.1 Effort 117 2.6.1 Seasonality and distribution of cetacean species 71 4.6.2 Data preparation and filtering 117 2.6.2 Caveats and recommendations 72 4.6.3 Comparison between WWV-data 2.7 Conclusion 75 and theodolite observations 121 2.8 Acknowledgements 75 4.7 Results 121 2.9 Literature 78 4.7.1 Effort 121 4.7.2 Temporal distribution patterns of cetacean species 125 4.7.3 Spatial distribution 125 4 © University of Pretoria 4.7.4 Behaviour 132 6 CONCLUDING REMARKS 183 4.7.5 Focal follows 137 6.1 Distribution, habitat use, and behaviour 183 4.7.6 Comparison between WWV-data 6.2 PAM 183 and theodolite sightings 140 6.3 Platforms of opportunity 185 4.8 Discussion 141 6.4 Conservation and management 186 4.8.1 Seasonality and distribution of cetacean species 141 6.5 Literature 187 4.8.2 Southern right whales 141 4.8.3 Humpback whales 142 7 APPENDIX 1 191 4.8.4 Bryde’s whales 143 7.1 The use of data from a platform of opportunity 4.8.5 Inshore dolphin species 143 (whale watching) to study coastal cetaceans on 4.8.6 Bias 144 the south west coast of South Africa 191 4.8.7 Inherent inaccuracy 144 4.8.8 Comparison between WWV-data 8 APPENDIX 2 214 and theodolite sightings 146 8.1 Data collection from commercial whale 4.9 Conclusions 146 watching vessel: the need for international 4.10 Acknowledgement 146 guidelines and systematic quality control 214 4.11 Literature 148 9 APPENDIX 3 221 5 PAssIVE ACOUSTIC MONITORING OF 9.1 Occurrence of vagrant leopard seals, SOUTHERN RIGHT WHALES 153 Hydrurga leptonyx, along the South African coast 221 5.1 Abstract 153 5.2 Key words 154 10 APPENDIX 4 225 5.3 Introduction 154 10.1 Possible non-offspring nursing in the 5.4 Methods 155 southern right whale, Eubalaena australis 225 5.4.1 Study site 155 5.4.2 Study setup 156 11 APPENDIX 5 238 5.4.3 Passive acoustic monitoring 157 11.1 Poster presentations 238 5.4.4 Land-based theodolite tracking 160 5.5 Data analysis 161 5.5.1 Passive acoustic monitoring 161 5.5.2 Signal to Noise Ratio (SNR) 164 5.5.3 Humpback whale vocalisations 164 5.5.4 Linking Acoustic and Visual data 165 5.6 Results 165 5.6.1 Passive acoustic monitoring 165 5.6.2 Southern right whale call analysis 168 5.6.3 Humpback whale call analysis 168 5.6.4 Land-based theodolite tracking 169 5.6.5 Passive acoustic monitoring & land-based theodolite tracking 174 5.7 Discussion 174 5.7.1 Passive acoustic monitoring 174 5.7.2 Bias and considerations 177 5.8 Conclusion 177 5.9 Acknowledgement 177 5.10 Literature 179 5 © University of Pretoria Southern right whale in question. PHOTO CREDIT KATJA VINDING PETERSEN 6 © University of Pretoria Summary This thesis is a study of the occurrence, behaviour, spatial distribution, and temporal distri- bution of cetaceans in the Greater Dyer Island area, Western Cape, South Africa. Three main methods were used in the study: Analysis of data from a local whale-watching vessel (WWV) (2000 – 2012), visual land-based theodolite tracking (during four southern right whale seasons (August – December) from 2011 – 2014 and one summer/autumn season in 2013), and passive acoustic monitoring (PAM) using a single bottom moored hydrophone (DSG-Ocean Loggerhead) in the months of January/February, September, and October, 2014). Methods were chosen, due to suitability, cost efficiency, and because they complement each other. Data from the WWV covered more than a ten-year period and provided indications of temporal and spatial distribution trends, but data were limited with respect to survey effort and behavioural data. Shore-based observations provided spatial, temporal, and behaviour patterns of the cetacean species in the area, but the method is labour intensive, requires daylight and is restricted by weather conditions. PAM could be conducted 24 hours a day and in poor weather conditions and enabled a temporal extension of the monitoring of cetaceans in the area, but individual hydrophones, are expensive and can break down or be lost. Simultaneous visual observations and PAM were used to investigate the vocalisation patterns of southern right whales and the possibility of using PAM to monitor presence of southern right whales. An analysis of the consistency and validity of the opportunistic data from the WWV was con- ducted before the data was used in a spatial and temporal analysis. The Consistency Index (CI) was defined as the proportion of times a data field was recorded per total number of trips during all years. The validity of the data were assessed to determine accuracy of the data. The validity and consistency analysis of the sighting records revealed that the dataset was useful but data fields varied considerably in their consistency of collection. The trip duration and route was recorded in less than 5% of cases, making analysis of temporal and spatial patterns difficult. The validity of species identification was excellent with 100% agreement between observer records and photographic documentation in 152 encounters of seven cetacean species. Behavioural data were described in overly subjective terms, thus not allowing for any analysis of patterns. The analysis also resulted in a list of suggestions for the design of future observa- tion sheets, and data collection methods and the development and implementation of world- wide standards are encouraged (guidelines and protocols), which should address different levels and scenarios of data collection from WWV. This work has made a novel contribution to the global research field by submission of a paper and direct communication with the whale watch- ing subcommittee at the International Whaling Commission (IWC) concerning content in the International guidelines for “platform of opportunity guiding principles on data collection”. An analysis of opportunistic cetacean sightings from the local WWV consisted of more than 5500 cetacean encounters during more than 2500 trips from 2003 to 2012.