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Abstract Trophic ecology and resource use are challenging to discern in migratory marine species, including sharks. However, effective management and conservation strategies depend on understanding these life history details. Here we investigate whether dental enameloid zinc isotope (δ66Znen) values can be used to infer intrapopulation differences in foraging ecology by comparing δ66Znenwith same-tooth collagen carbon and nitrogen (δ13Ccoll, δ15Ncoll) values from critically endangered sand tiger sharks (Carcharias taurus) from Delaware Bay (USA). We document ontogeny and sex-related isotopic differences indicating distinct diet and habitat use at the time of tooth formation. Adult females have the most distinct isotopic niche, likely feeding on higher trophic level prey in a distinct habitat. This multi-proxy approach characterises an animal’s isotopic niche in greater detail than traditional isotope analysis alone and shows that δ66Znenanalysis can highlight intrapopulation dietary variability thereby informing conservation management and, due to good δ66Znenfossil tooth preservation, palaeoecological reconstructions.
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This content will become publicly available on May 21, 2026
Trophic Ecology of Threatened Sympatric Coastal Dolphins and Other Odontocetes in North‐Western Madagascar
ABSTRACT Investigating the foraging ecology and trophic interactions of threatened marine predators is critical to assess how community changes due to anthropogenic activities will affect predator–prey relationships. Two species of threatened coastal dolphins, the Indian Ocean humpback dolphin (Sousa plumbea) and the Indo‐Pacific bottlenose dolphin (Tursiops aduncus), occur off Nosy Be, north‐western Madagascar, in a region where artisanal fisheries are ecologically and socioeconomically important. Here, we investigated the feeding ecology of these two coastal dolphins and their trophic interactions with four other odontocetes using bulk stable carbon and nitrogen isotope analysis (δ13C andδ15N). Humpback dolphins had significantly enrichedδ13C values, reflecting a preference for coastal/benthic prey. Bottlenose dolphins had a broader isotopic niche, suggesting a broader range of prey and foraging habitats. The overlap in isotopic niche of all six odontocete species was limited, indicating partitioning of resources and habitats. Bayesian mass‐balance isotopic mixing models revealed that humpback dolphins forage primarily on reef planktivores (38.9%) and inner reef mesopredators (20.5%), while bottlenose dolphins had a broader diet, including reef‐associated (15%–32%) and pelagic prey (12%–23%). Our study reveals that the reliance on inshore prey by humpback dolphins may place them in competition with coastal fisheries.
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- Award ID(s):
- 1827195
- PAR ID:
- 10643304
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Marine Mammal Science
- Volume:
- 41
- Issue:
- 4
- ISSN:
- 0824-0469
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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