Limited trophic partitioning among sympatric delphinids off a tropical oceanic atoll

PLoS One. 2017 Aug 2;12(8):e0181526. doi: 10.1371/journal.pone.0181526. eCollection 2017.

Abstract

Understanding trophic relationships among marine predators in remote environments is challenging, but it is critical to understand community structure and dynamics. In this study, we used stable isotope analysis of skin biopsies to compare the isotopic, and thus, trophic niches of three sympatric delphinids in the waters surrounding Palmyra Atoll, in the Central Tropical Pacific: the melon-headed whale (Peponocephala electra), Gray's spinner dolphin (Stenella longirostris longirostris), and the common bottlenose dolphin (Tursiops truncatus). δ15N values suggested that T. truncatus occupied a significantly higher trophic position than the other two species. δ13C values did not significantly differ between the three delphinds, potentially indicating no spatial partitioning in depth or distance from shore in foraging among species. The dietary niche area-determined by isotopic variance among individuals-of T. truncatus was also over 30% smaller than those of the other species taken at the same place, indicating higher population specialization or lower interindividual variation. For P. electra only, there was some support for intraspecific variation in foraging ecology across years, highlighting the need for temporal information in studying dietary niche. Cumulatively, isotopic evidence revealed surprisingly little evidence for trophic niche partitioning in the delphinid community of Palmyra Atoll compared to other studies. However, resource partitioning may happen via other behavioral mechanisms, or prey abundance or availability may be adequate to allow these three species to coexist without any such partitioning. It is also possible that isotopic signatures are inadequate to detect trophic partitioning in this environment, possibly because isotopes of prey are highly variable or insufficiently resolved to allow for differentiation.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Behavior, Animal
  • Biopsy
  • Dolphins / classification
  • Dolphins / physiology*
  • Ecosystem
  • Feeding Behavior / physiology*
  • Food Chain
  • Nutritional Status
  • Remote Sensing Technology
  • Skin / chemistry*

Grants and funding

Research was supported by funding from the National Oceanic and Atmospheric Administration Pacific Islands Fisheries Science Center, the Southwest Fisheries Science Center, the Office of Science and Technology Ocean Acoustics Program, the National Geographic Waitt Foundation (W9-08), the U.S. Marine Mammal Commission, and the U.S. Navy Chief of Naval Operation-N45. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.