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Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea)
Thesis (PhD)--Stellenbosch University, 2025.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867614026054238208 |
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| access_status_str | Open Access |
| author | Dines, Sasha Francess |
| author2 | Measey, John |
| author_browse | Dines, Sasha Francess Measey, John |
| author_facet | Measey, John Dines, Sasha Francess |
| author_sort | Dines, Sasha Francess |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132009 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:45:29.584Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132009 Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea) Dines, Sasha Francess Measey, John Gridley, Tess Elwen, Simon Stellenbosch University. Faculty of Science. Dept. of Botany & Zoology. Marine mammals -- Monitoring -- Data processing Indian Ocean humpback dolphin -- Conservation -- South Africa Passive acoustic monitoring -- Technique Dolphins -- Behavior Indian Ocean humpback dolphin -- Effect of human beings on Sousa -- Habitat -- South Africa UCTD Thesis (PhD)--Stellenbosch University, 2025. Dines, S. F. 2025. Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea). Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/ba08fdd7-4a00-4367-b6fd-f7dd10e309c6 ENGLISH ABSTRACT: Monitoring is crucial for conservation, but elusive species, including some species of coastal delphinids, represent particular challenges. Traditional visual surveys can often underestimate metrics such as abundance. For Indian Ocean humpback dolphins (Sousa plumbea) in South Africa, near-shore habitats and low encounter rates hinder photographic data collection. Passive acoustic monitoring (PAM) offers a non-invasive alternative for species monitoring. This thesis investigates the whistling behaviour of S. plumbea in South Africa, focusing on exploring the use of signature whistles for individual acoustic detection. Using boat-based recordings (2016–2023) from five sites throughout their South African range, it examines whistle variation across different geographic scales (including a comparison of whistle-contour time-frequency parameters across the extremes of the entire geographic range of the species) and the effect of group composition and behaviour on signature whistle production rates, aiming to optimise passive acoustic detection methods. The efficacy of individual acoustic detection using PAM was directly compared to visual detection (Photo ID) through a two-week survey period in Mossel Bay. Following this, an extended acoustic monitoring period along a portion of the south coast subpopulation investigated individual acoustic monitoring across three sites, using five hydrophones over six weeks, providing abundance estimates, as well as density estimates generated using spatially explicit capture-recapture (SECR). Macrogeographic variation in whistle contours was evident between South Africa and India, two populations at the furthest extent of the species' geographic range (Random Forest model correct classification rate; South Africa 84% (35.2% chance) and India 93% (64.8% chance)). Moderate variation within South Africa ranged from 39–90% across study sites, indicating increased acoustic variation with geographic distance. Group composition factors such as group size, group spread, calf presence, and behaviour had little impact on signature whistle production. These findings suggest that these factors are not crucial for optimising the detection of signature whistles in the acoustic monitoring of S. plumbea. Comparing monitoring methods, photographic identification was more cost-effective (6,400 ZAR.dolphin-1) than acoustic methods (12,266.40 ZAR.dolphin-1). However, acoustic detection was diurnal, identifying more individuals and signature whistles at night and across the entire survey area. Visual surveys detected dolphins at only two locations, emphasising PAM's effectiveness as an alternative method for detecting S. plumbea. Abundance estimates from signature whistle detected along a 120 km stretch of South Africa's south coast revealed limited individual movement, with low abundance (SECR: 23–26; POPAN: 26, 95% CI 23–30) and density (0.000061–0.000439 animals.ha-1). This proof-of-concept study explored mooring configurations and model optimisation, demonstrating that expanding the geographic range of the acoustic array could be more effective for increasing unique recaptures than clustering acoustic receivers in a smaller area. This thesis demonstrates that PAM is a reliable alternative to photographic surveys to study the elusive coastal species S. plumbea and produces sufficient data to understand population abundances and movements using individual acoustic signatures. These techniques offer a scalable and reproducible approach to producing population estimates, which can equip wildlife practitioners and scientists with the tools to monitor this elusive species reliably over time and space. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2025-05-16T07:45:22Z 2025-05-16T07:45:22Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132009 en Stellenbosch University 304 pages : illustrations (some color), maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Marine mammals -- Monitoring -- Data processing Indian Ocean humpback dolphin -- Conservation -- South Africa Passive acoustic monitoring -- Technique Dolphins -- Behavior Indian Ocean humpback dolphin -- Effect of human beings on Sousa -- Habitat -- South Africa UCTD Dines, Sasha Francess Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea) |
| title | Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea) |
| title_full | Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea) |
| title_fullStr | Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea) |
| title_full_unstemmed | Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea) |
| title_short | Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea) |
| title_sort | applied passive acoustic monitoring of south africa s most threatened marine mammal the indian ocean humpback dolphin sousa plumbea |
| topic | Marine mammals -- Monitoring -- Data processing Indian Ocean humpback dolphin -- Conservation -- South Africa Passive acoustic monitoring -- Technique Dolphins -- Behavior Indian Ocean humpback dolphin -- Effect of human beings on Sousa -- Habitat -- South Africa UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132009 |
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