New Zealand Journal of Zoology abstracts

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Stable carbon isotope ratios as indicators of marine versus terrestrial inputs to the diets of wild and captive tuatara (Sphenodon punctatus)

ALISON CREE

Department of Zoology
University of Otago
P.O. Box 56
Dunedin, New Zealand
email: alison.cree@stonebow.otago.ac.nz

GRAEME L. LYON

Institute of Geological and Nuclear Sciences
P.O. Box 31312
Lower Hutt, New Zealand

LINDA CARTLAND-SHAW
CLAUDINE TYRRELL

Department of Zoology
University of Otago
P.O. Box 56
Dunedin, New Zealand

Abstract  Stable carbon isotope analysis was used to examine feeding relationships of wild tuatara on Stephens Island and captive tuatara in New Zealand institutions. We first measured d¹³C in three food items of wild tuatara. Pectoral muscle of fairy prions (a seabird eaten seasonally by tuatara) was significantly enriched in ¹³C compared with whole bodies of wild insects (darkling beetles and tree weta). Values for d¹³C in blood cells varied significantly among wild tuatara of different life-history stages. Male tuatara were more enriched in ¹³C than were females or juveniles, suggesting that males prey more heavily on seabirds. Insect foods of captive tuatara varied dramatically in d¹³C; this is attributed to differential consumption of plant material derived from the C3 and C4 photosynthetic pathways. Blood cells from four different groups of captive tuatara differed significantly in d¹³C. This was perhaps related to assimilation of insects with different d¹³C values, and cannot be attributed to differences in seabird predation as captive tuatara do not have access to seabirds. For wild tuatara on Stephens Island, stable carbon isotope analysis provides support for the dietary information available from behavioural observations, gut analyses and measurements of plasma composition.

Keywords  tuatara; Sphenodon punctatus; fairy prion; Pachyptila turtur; stable isotope analysis; carbon-13; marine versus terrestrial diets

Z98033
Received 31 July 1998; accepted 10 March 1999

PDF file of entire paper: medium quality (922K); (scanned from paper original: notes about this process)

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