Investigating Fiordland penguin/tawaki foraging plasticity using stable isotope analysis.

ELLENBERG, URSULA; SEDDON, PHIL; MAYS, HERMAN; MATTERN, THOMAS; WHITE, JEFF; HOUSTON, DAVID; GARCIA BORBOROGLU, P.; CROWLEY, BROOKE; HOPKINS, JOHN III

Dunedin

Congreso; International Penguin Congress; 2019

University of Otago

Fiordland penguins or tawaki (Eudyptes pachyrhynchus) depend on the abundant resources of the Tasman Sea to ensure reproductive success and to build fat reserves to sustain them during the molting fast. Environmental change impacts prey distribution and abundance, requiring penguins to change their foraging behavior. Tawaki occupy a broad range of marine ecosystems suggesting they have higher diet plasticity than most other penguin species. To assess differences in foraging strategies between sexes and among locations, we compared stable isotope (SI) ratios (13C/12C and 15N/14N, expressed as δ13C and δ15N values) in penguins from sites associated with marine environments characterized as pelagic, continental shelf, or fjord. We analyzed SI ratios in blood (which integrates prey intake during ca. 2 weeks prior to sampling), and feathers (which represent diet during feather formation and the pre-moult dispersal). We used stable isotope mixing models to conduct a preliminary reconstruction of penguin diet in each location. Although we found that stable isotope values did not differ between sexes, they did vary among locations, suggesting that penguins use different foraging strategies in each habitat. As climate change continues to affect marine ecosystems, detailed investigation of tawaki foraging ecology will be critical for understanding how penguins will respond. We will use the results from this study to estimate dietary parameters to predict reproductive success and survival of tawaki under different climate scenarios.