Foraging preferences of an apex marine predator revealed through stomach content and stable isotope analyses

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  • S. M. McCluskey, Murdoch University
  • ,
  • K. R. Sprogis
  • J. M. London, NOAA
  • ,
  • L. Bejder, Environmental and Conservation Sciences, Murdoch University, Centre for Sustainable Aquatic Ecosystems, Marine Mammal Research Program, University of Hawaii at Manoa
  • ,
  • N. R. Loneragan, Murdoch University

Insights into the food habits of predators are essential for maintaining healthy predator populations and the functioning of ecosystems. Stomach content and stable isotope analyses were used to investigate the foraging habits of an apex predator, the Indo-Pacific bottlenose dolphin (Tursiops aduncus) in south-western Australia. A total of 2,594 prey items from 26 families were identified from the stomachs of 10 deceased stranded dolphins. Fish otoliths from stomach contents were used to identify fish to family or species level. Ninety-three percent of identified stomach contents were perciforme fishes, however, perciformes comprised only 30% of the catch during prey sampling. Gobiidae species, small fish generally <100 mm in total length, were the most prevalent family identified in dolphin stomachs, accounting for 82% of identified prey, yet Gobiidae accounted for 12.7% of the catch during prey sampling. For stable isotope analyses, tissue samples from 14 free-ranging dolphins were analyzed for nitrogen (δ15N) and carbon (δ13C) ratios. From stable isotope analyses and boat-based dolphin photo-identification surveys (n = 339, 2007–2011), results indicated niche differentiation between coastal and inshore (bay and estuarine habitat) dolphins. Carbon signatures showed that coastal dolphins had a more pelagic diet compared to a benthic diet observed in the inshore dolphins. Whereas, nitrogen signatures of inshore dolphins showed higher nitrogen levels than coastal dolphins, likely attributed to feeding on enriched prey typical of estuarian environments. Overall, these results indicated that bottlenose dolphins in the study area were selective foragers and that their foraging is specialized by the habitats most frequently used.

OriginalsprogEngelsk
Artikelnummere01396
TidsskriftGlobal Ecology and Conservation
Vol/bind25
Antal sider20
ISSN2351-9894
DOI
StatusUdgivet - jan. 2021

Bibliografisk note

Funding Information:
This study was funded by SWMRP partners: Bemax Cable Sands, BHP Billiton Worsley Alumina ltd., the Bunbury Dolphin Discovery Centre, Bunbury Port Authority, City of Bunbury, Cristal Mining, the Western Australian Department of Parks and Wildlife, Iluka, Millard Marine, Naturaliste Charters, Newmont Boddington Gold, South West Development Commission, and WA Plantation Resources. SMM was supported for 3.5 years of her Ph.D. with a Murdoch University International Scholarship. This paper represents HIMB and SOEST contribution numbers 1839 and 11214, respectively.

Funding Information:
We thank the following people for their assistance with prey sampling data collection: C. Birdsall, A. Brown, A. Cesario, D. Cori, H. Cross, V. Gillmann, L. Howes, A. Mail, and S. Osterrieder. We are appreciative to H. Raudino and the South West Marine Research Program (SWMRP) associates for running dolphin field seasons, and numerous assistants and interns for help in the field during dolphin surveys. We thank S. Allen, D. McElligott, and A. Sellas for obtaining dolphin biopsy samples as a part of a broader study, and C. Daniel, A. Kopps, and O. Manlik for dolphin sexing results. S. McLachlan and N. Stephens assisted in obtaining dolphin stomachs during dolphin necropsies. We would also like to thank the reviewers of this article. This study was funded by SWMRP partners: Bemax Cable Sands, BHP Billiton Worsley Alumina ltd., the Bunbury Dolphin Discovery Centre, Bunbury Port Authority, City of Bunbury, Cristal Mining, the Western Australian Department of Parks and Wildlife, Iluka, Millard Marine, Naturaliste Charters, Newmont Boddington Gold, South West Development Commission, and WA Plantation Resources. SMM was supported for 3.5 years of her Ph.D. with a Murdoch University International Scholarship. This paper represents HIMB and SOEST contribution numbers 1839 and 11214, respectively.

Publisher Copyright:
© 2020 The Authors

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

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