Wanted: dead or alive? Isotopic analysis (δ13C and δ15N) of Pygoscelis penguin chick tissues supports opportunistic sampling.

RATIONALE

Physiological stress and starvation have been shown to affect δ(13)C and δ(15)N isotope values and, given that animals often die from starvation, the cause of death may be an important factor to consider in stable isotope analyses of opportunistically collected samples.

METHODS

We addressed this issue by comparing tissue stable isotope values of living and deceased Adélie (Pygoscelis adeliae) and Chinstrap Penguin (P. antarctica) chicks collected from the same respective populations.

RESULTS

No significant difference was found between living and deceased penguin chick feather, down, and toenail isotope values and both groups displayed similar isotopic trends between tissue types. In addition, similar relationships were observed between both species and across several seasons. Furthermore, sub-dermal adiposity and cause of death (starvation and/or predation) had no significant effect on the δ(13)C and δ(15)N values.

CONCLUSIONS

Our findings suggest that tissues from deceased penguins can be isotopically representative of tissues obtained from the living population, despite the cause of death, and support the use of opportunistic sampling in stable isotope analyses.