A. Cree et al., Stable carbon isotope ratios as indicators of marine versus terrestrial inputs to the diets of wild and captive tuatara (Sphenodon punctatus), NZ J ZOOLOG, 26(3), 1999, pp. 243-253
Stable carbon isotope analysis was used to examine feeding relationships of
wild tuatara on Stephens Island and captive tuatara in New Zealand institu
tions. We first measured delta(13)C in three food items of wild tuatara. Pe
ctoral muscle of fairy prions (a seabird eaten seasonally by tuatara) was s
ignificantly enriched in C-13 compared with whole bodies of wild insects (d
arkling beetles and tree weta). Values for delta(13)C in blood cells varied
significantly among wild tuatara of different life-history stages. Male tu
atara were more enriched in C-13 than were females or juveniles, suggesting
that males prey more heavily on seabirds. Insect foods of captive tuatara
varied dramatically in delta(13)C; this is attributed to differential consu
mption of plant material derived from the C-3 and C-4 photosynthetic pathwa
ys. Blood cells from four different groups of captive tuatara differed sign
ificantly in delta(13)C. This was perhaps related to assimilation of insect
s with different delta(13)C values, and cannot be attributed to differences
in seabird predation as captive tuatara do not have access to seabirds. Fo
r 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.