Corticosterone levels, leukocyte profiles, and foraging and diving behaviours of Humboldt penguins during chick rearing in Northern Chile

ABSTRACT

Understanding the physiology of stress in wild animals is essential for the conservation of species subject to anthropogenic perturbations. Humboldt penguins (Spheniscus humboldti) are exposed to increasing anthropogenic impacts in their natural habitat. In this species, females are typically smaller and dive less deep than males. In related species, the more limited foraging habitat of females and their reduced resiliency due to their smaller size were associated with higher mortality. We hypothesise that potential sex-specific differences in the foraging behaviour of Humboldt penguins may also relate to differences in their physiological stress. Here, we studied sex-specific foraging and diving behaviours and variations in plasma corticosterone levels and leukocyte profiles of Humboldt penguins during the chick-rearing period in Northern Chile. We report no evidence of sex-related differences in most foraging parameters, except that males dived significantly deeper than females. We found that plasma corticosterone levels and leukocyte profiles showed no significant differences between the sexes. Furthermore, there was no clear relationship between an individual’s foraging behaviour and its plasma corticosterone level or leukocyte profile. In summary, we found no support for sex-related differences in physiological stress levels of Humboldt penguins, and no link between their foraging behaviour and their physiological stress. However, we acknowledge that our sample size is small and that more studies are needed. This study contributes with information on the physiological stress and foraging behaviours of Humboldt penguins in Northern Chile. This information can help to understand context-dependent differences in physiological parameters and foraging behaviours for the species.

KEYWORDS:

• penguin
• Chile
• diving
• foraging
• sex-related differences

Acknowledgements

We thank Wolfgang Goymann and Monika Trappschuh from the Max Planck Institute for Ornithology in Germany for their collaboration with the hormone analysis. Special thanks go to Nicolas Gouin and Paula Plaza for their professional advice regarding the sexing analysis and the Centro de Estudios Avanzados en Zonas Áridas (CEAZA) for allowing us to use their facilities to conduct this analysis. We thank Esther Rickert for the transportation of tracking devices, and Henri Kröling for useful discussions. We thank the reviewers who provided thoughtful recommendations that improved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Ethics statement

This study was conducted according to Subsecretaría de Pesca y Acuicultura de Chile permit resolution no. 3367/2017, in line with the applicable international ethical standards for the care and use of wild animals. The procedures were performed by qualified veterinarians under the regulations and supervision of local authorities.

Supplementary material

Supplemental data for this article can be accessed at https://doi.org/10.1080/01584197.2022.2153699

Additional information

Funding

This study was financed by Fondecyt postdoctorate (grant no. 3170936 to RQ) and the Research and Technology Centre (FTZ), University of Kiel. ML received support from CONACyT-INAPI (grant no. 411876). CV received support from Fondecyt postdoctorate (grant no. 3160679). RQ received support from Convocatoria Nacional Subvención a la Instalación en la Academia 2021 (grant no. SA77210088-ANID-Chile).