Reassessment of the cardio-respiratory stress response, using the king penguin as a model
Résumé
Research in to short-term cardio-respiratory changes in animais in reaction to a psychological
stressor typically describes increases in rate of oxygen consumption (Vo,) 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 mavement levels in a sedentary yet
free-ta-mave 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 Va, and heart rate when exposed ta the stressor. Hawever, mavement levels, while still
law, also increased in respanse ta the stressar. Once this was accaunted for by camparing
periads oftime during the control and stress conditions when movement levels were similar as
recorded by the accelerometers, only Va, 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 cardia-respiratary respanse per se ta a psycholog ical
stressor (Le. the respanse as a result of physialagical changes directly attributable to the
stressar) is an increase in Vo, withaut an increase in heart rate.