Reassessment of the cardio-respiratory stress response, using the king penguin as a model

Abstract

Research in to short-term cardio-respiratory changes in animals in reaction to a psychological stressor typically describes increases in rate of oxygen consumption () and heart rate. Consequently, the broad consensus is that they represent a fundamental stressor response generalizable across adult species. However, movement levels can also change in the presence of a stressor, yet studies have not accounted for this possible confound on heart rate. Thus the direct effects of psychological stressors on the cardio-respiratory system are not resolved. We used an innovative experimental design employing accelerometers attached to king penguins (Aptenodytes patagonicus) to measure and thus account for movement levels in a sedentary yet free-to-move animal model during a repeated measures stress experiment. As with previous studies on other species, incubating king penguins (N = 6) exhibited significant increases in both and heart rate when exposed to the stressor. However, movement levels, while still low, also increased in response to the stressor. Once this was accounted for by comparing periods of time during the control and stress conditions when movement levels were similar as recorded by the accelerometers, only significantly increased; there was no change in heart rate. These findings offer evidence that changing movement levels have an important effect on the measured stress response and that the cardio-respiratory response per se to a psychological stressor (i.e. the response as a result of physiological changes directly attributable to the stressor) is an increase in without an increase in heart rate.

• Accelerometer
• heart rate
• king penguin
• oxygen consumption
• psychological stressor
• respirometry

Acknowledgements

We thank the French Polar Institut (Institut Polaire Paul Emile Victor) for their financial and logistical support in realising this study. Marguerite Netchaieff gave invaluable help during data collection. Nicholas Decalmer built the respirometer chamber for the experiments. We would also like to thank Anne Robertson, René Groscolas, Charles-André Bost, Laëtitia Maréchal, Stuart Semple and Nils Arrigo for their advice during data collection, data analyses and manuscript writing.

Declaration of interest

The authors report no conflicts of interests. The Swiss Fund for Women at University (Association Suisse des femmes diplômées des universités), the Company of Biologists and the Society for Experimental Biology provided funding for this study.