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Size-based differences in isotopic niche width (δC and δN) of green turtles (Chelonia mydas) nesting on Príncipe Island, Gulf of Guinea

Marine Ecology, ISSN: 1439-0485, Vol: 42, Issue: 1
2021
  • 4
    Citations
  • 0
    Usage
  • 14
    Captures
  • 0
    Mentions
  • 11
    Social Media
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  • Citations
    4
  • Captures
    14
  • Social Media
    11
    • Shares, Likes & Comments
      11
      • Facebook
        11

Article Description

Within the same population, nesting green turtles (Chelonia mydas) might exploit different niches by exhibiting polymorphic foraging strategies and/or inhabiting geographically distinct foraging areas. This is crucial information for the conservation of this species. Here, we used stable carbon and nitrogen isotope ratios (δC and δN) to test for differences in a population of green turtles nesting on Príncipe Island (1°37′N; 7°24҆′E), Central Africa. A total of 60 nesting females were sampled on the two main nesting beaches of the island in December 2012. Minimum curved carapace length (CCL) was recorded, and δC and δN values were measured in the epidermis of each individual. Overall, CCL varied from 87.0 to 108.0 cm (mean ± SD =100.0 ± 5.1), δC values from −19.4 to −8.6‰ (−17.3 ± 1.8) and δN values from 7.9 to 17.3‰ (13.6 ± 1.5). Despite the large variation in both isotopic ratios, their distributions were unimodal, showing an absence of polymorphic foraging strategies and isotopically distinct foraging areas. However, smaller females (< median, 100.8 cm) occupied a much larger isotopic niche (i.e., four times greater) than larger females. These results suggest that nesting green turtles may forage opportunistically on the resources available in each of their foraging home ranges, with smaller females venturing to more isotopic-diversified areas and/or exhibiting broader foraging strategies than larger females. In addition, and in accordance with other studies, findings suggest that the foraging grounds used by the Príncipe green turtle nesting females are distributed mainly throughout the Gulf of Guinea.

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