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Spatial and Temporal Variations in the Occurrence and Foraging Activity of Coastal Dolphins in Menai Bay, Zanzibar, Tanzania

Lookup NU author(s): Dr Andrew Temple, Professor Per Berggren

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

Understanding temporal patterns in distribution, occurrence and behaviour is vital for theeffective conservation of cetaceans. This study used cetacean click detectors (C-PODs) toinvestigate spatial and temporal variation in occurrence and foraging activity of the Indo-Pacific bottlenose (Tursiops aduncus) and Indian Ocean humpback (Sousa plumbea) dolphinsresident in the Menai Bay Conservation Area (MBCA), Zanzibar, Tanzania. Occurrencewas measured using detection positive minutes. Inter-click intervals were used toidentify terminal buzz vocalisations, allowing for analysis of foraging activity. Data were analysedin relation to spatial (location) and temporal (monsoon season, diel phase and tidalphase) variables. Results showed significantly increased occurrence and foraging activityof dolphins in southern areas and during hours of darkness. Higher occurrence at night wasnot explained by diel variation in echolocation rate and so were considered representativeof occurrence patterns. Both tidal phase and monsoon season influenced occurrence butresults varied among sites, with no general patterns found. Foraging activity was greatestduring hours of darkness, High water and Flood tidal phases. Comparisons of echolocationdata among sites suggested differences in the broadband click spectra of MBCA dolphins,possibly indicative of species differences. These dolphin populations are threatened byunsustainable fisheries bycatch and tourism activities. The spatial and temporal patternsidentified in this study have implications for future conservation and management actionswith regards to these two threats. Further, the results indicate future potential for using passiveacoustics to identify and monitor the occurrence of these two species in areas wherethey co-exist.

Publication metadata

Author(s): Temple AJ, Tregenza N, Amir OA, Jiddawi N, Berggren P

Publication type: Article

Publication status: Published

Journal: PLoS ONE

Year: 2016

Volume: 11

Issue: 3

Online publication date: 02/03/2016

Acceptance date: 25/01/2016

Date deposited: 21/03/2016

ISSN (electronic): 1932-6203

Publisher: Public Library of Science

URL: http://dx.doi.org/10.1371/journal.pone.0148995

DOI: 10.1371/journal.pone.0148995

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