MEPS 166:277-284 (1998)  -  doi:10.3354/meps166277

The trophic status of marine turtles as determined by stable isotope analysis

B. J. Godley1,2,*, D. R. Thompson1,**, S. Waldron3, R. W. Furness1

1Division of Environmental and Evolutionary Biology, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom 2Department of Veterinary Anatomy, University of Glasgow Veterinary School, Glasgow G61 1QH, United Kingdom 3Scottish Universities Research and Reactor Centre, Scottish Technology Park, East Kilbride, Glasgow G75 OQU, United Kingdom
*E-mail:
**Present address: National Institute of Water & Atmospheric Research, 301 Evans Bay Parade, Greta Point, PO Box 14-901, Kilbirnie, Wellington, New Zealand

Stable isotope ratios of nitrogen and carbon were determined in bone collagen, egg proteins and keratin from epidermal carapace scutes of loggerhead Caretta caretta, green Chelonia mydas, and leatherback Dermochelys coriacea turtles from the Mediterranean Sea and the European Atlantic Ocean. Isotope ratios in proteins from loggerhead turtles indicate that this species occupies a higher trophic position than green turtles. Leatherback turtles are apparently intermediate in trophic status. Within loggerhead turtles, both isotope ratios correlated positively with body size, indicating a trend of increasing trophic level with age. Within the size range of green turtles sampled, there was apparently no change in trophic level in relation to body size. In absolute terms, isotope signatures of egg proteins were markedly different from those of bone collagen. However, inter-specific differences in isotope values were consistent with those in bone protein. The novel application of this technique to marine turtles generally confirmed dietary information collected conventionally in these species and has also afforded additional insights into shifts in diet and trophic status as turtles mature.


Feeding ecology · Caretta caretta · Chelonia mydas · Dermochelys coriacea · Mediterranean · Carbon · Nitrogen


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