FORAGING STRATEGY PLASTICITY IN FIORDLAND PENGUINS (EUDYPTES PACHYRHYNCHUS): A STABLE ISOTOPE APPROACH

Author

Jeffrey Wayne WhiteFollow

Date of Award

2020

Degree Name

Biology

College

College of Science

Type of Degree

M.S.

Document Type

Thesis

First Advisor

Dr. Herman Mays, Committee Chairperson

Second Advisor

Dr. Anne Axel

Third Advisor

Dr. Jennifer Mosher

Fourth Advisor

Dr. John Hopkins III

Abstract

Foraging ecology in the crested penguins (genus: Eudyptes) is an active area of research, with new techniques rapidly increasing our understanding of these charismatic species. The most common techniques to assess foraging ecology include stomach content analysis, fecal DNA analysis, stable isotope analysis, tracking, and video loggers. Here we review dietary research on all 8 taxa within the genus Eudyptes to identify gaps in our current knowledge. However, foraging studies that assess dietary segregation require a method for quickly and accurately sexing penguins in the field. Obvious sexual dimorphism in plumage is largely absent in penguins leaving behavioral cues for sex determination. We identified morphological characters that could be easily measured in the field to predict sex in the Fiordland penguin (tawaki; Eudyptes pachyrhynchus) by assessing the correlation between five morphological metrics and individual sex as determined by a PCR-based molecular approach. We found that a combination of foot length and either bill length or bill depth was the most accurate morphological approach to determine individual sex in the field. Finally, to identify differences in foraging strategies in tawaki among marine habitat types (pelagic, continental shelf, or fjord), we analyzed stable isotope ratios of carbon (¹³C/¹²C, expressed as δ¹³C values) and nitrogen (¹⁵N/¹⁴N, expressed as δ¹⁵N values) in penguin blood and feathers. We found that both δ¹³C and δ¹⁵N values differed significantly between tissues. During incubation (blood), δ¹⁵N values were highest in the fjord and δ¹³C values differed significantly between years. In the pre-molt period (feathers), δ¹³C values were significantly different among sites, between sexes, and between certain years. δ¹⁵N values were only different between certain years. Monitoring the foraging ecology of tawaki and other crested penguins is critical for understanding population responses to changing prey distributions in a warming ocean.

Subject(s)

Penguins -- Research.

Penguins -- Life cycles.

Penguins -- Behavior.

Recommended Citation

White, Jeffrey Wayne, "FORAGING STRATEGY PLASTICITY IN FIORDLAND PENGUINS (EUDYPTES PACHYRHYNCHUS): A STABLE ISOTOPE APPROACH" (2020). Theses, Dissertations and Capstones. 1284.
https://mds.marshall.edu/etd/1284