Resource partitioning among South African delphinids

    Authors

    N. E. Browning; V. G. Cockcroft;G. A. J. Worthy

    Comments

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    Abbreviated Journal Title

    J. Exp. Mar. Biol. Ecol.

    Keywords

    Feeding ecology; Habitat utilization; Isotopic niche-width; Stable; isotopes; BOTTLE-NOSED DOLPHINS; NITROGEN ISOTOPE RATIOS; STABLE-ISOTOPE; TURSIOPS-TRUNCATUS; COMMON DOLPHINS; ODONTOCETE CETACEANS; SOCIAL-ORGANIZATION; NORTHEAST ATLANTIC; HUMPBACK DOLPHINS; STOMACH; CONTENTS; Ecology; Marine & Freshwater Biology

    Abstract

    In order to better understand trophic relationships among four species of coastal delphinids, we compared isotopic composition of skin to attempt to assess potential inter- and intra-specific resource partitioning. Skin samples were collected from Indo-Pacific bottlenose dolphins (Tursiops aduncus) (n = 132), long-beaked common dolphins (Delphinus capensis) (n = 78), humpback dolphins (Sousa chinensis) (n = 27), and striped dolphins (Stenella coeruleoalba) (n = 3) along the coastline of South Africa. While the latter species tends to be found offshore, the other species have overlapping distributions and feed on similar prey, carbon (delta C-13) and nitrogen (delta N-15) isotope analyses revealed resource partitioning with differences in diet and habitat use. Striped dolphin delta C-13 values (-16.97 +/- 0.25 parts per thousand, SD) were consistent with evidence that they typically forage offshore, while delta C-13 values of humpback dolphins reflected their use of inshore habitats (-15.16 +/- 0.65 parts per thousand). Common and bottlenose dolphins had delta C-13 (-15.48 0.66 parts per thousand and -15.76 +/- 0.71 parts per thousand respectively) values that fell between these two extremes. Mean values for delta N-15 ranged from 11.92 +/- 0.20 parts per thousand for striped dolphins to 15.19 +/- 0.73 parts per thousand, for humpback dolphins, suggesting either that these species were feeding at different trophic levels or that they were feeding in different trophic systems. Common and bottlenose dolphins had delta N-15 values of 13.49 +/- 0.50 parts per thousand and 14.40 +/- 0.74 parts per thousand respectively. Male bottlenose dolphins were significantly more enriched in delta N-15 compared to females suggesting dietary differences. No sex related differences were found in other species. Isotopic niche width determinations using corrected standard elliptical area (SEA,) were calculated. Humpback and bottlenose dolphins had the largest SEA, reflecting a broader trophic niche, while striped dolphins had the smallest SEA, reflecting a more specialized niche. Overall, these sympatric species appear to reduce potential competitive pressure through a combination of differing prey selection and habitat utilization. (C) 2014 Elsevier B.V. All rights reserved.

    Journal Title

    Journal of Experimental Marine Biology and Ecology

    Volume

    457

    Publication Date

    1-1-2014

    Document Type

    Article

    Language

    English

    First Page

    15

    Last Page

    21

    WOS Identifier

    WOS:000337868700003

    ISSN

    0022-0981

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