Exploring techniques to assess stress-related physiological responses in captive African penguins

TL;DR

This study explores methods to measure stress in captive African penguins, including heart rate monitoring and hormone analysis in blood, feathers, and urofaeces.

Contribution

The study introduces a novel heart rate recorder and evaluates the utility of glucocorticoid measurements in different biological samples for stress assessment in penguins.

Findings

Heart rate recorders captured immediate stress responses but require design improvements for consistent data.

Urofaecal glucocorticoid metabolites offer a minimally invasive way to assess long-term stress.

Feather glucocorticoids reflect integrated stress over time but require further research to clarify their interpretation.

Abstract

As animals experience a range of stressors, monitoring their stress response is important in conservation management and animal welfare practices. This study investigated possible techniques for evaluating stress-response in captive African penguins (Spheniscus demersus), including recording heart rate (HR) with a novel recorder inside a dummy egg, quantifying glucocorticoids in serum (sGC) and feathers (fGC) and glucocorticoid metabolites (ufGCM) in urofaeces.

● The HR recorders allowed for an assessment of immediate responses to stressors, however improvements in the design are necessary to record more consistent HR data.

● SGCs provide an assessment of an immediate stress response to acute stressors, however, due to the invasive nature of sampling this technique should only be used when blood is being drawn for medical reasons. UfGCM concentrations are less sensitive to short-term perturbations due to the accumulation of GC metabolites over longer periods, and due to the minimally invasive sampling procedure, allow for resampling, providing a useful tool for assessing long-term stress-related physiological response and welfare. FGC concentrations represent an integration of hypothalamic pituitary-adrenal activity over a period of days/weeks, however, whether this reflects circulating baseline levels or significant stressful events during feather growth is unclear and further research is needed to determine this.

Image, graphical abstract

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