Temperature and heart rate as stress indicators of handled common eider

Three eider ducks were handled every 4 min for 16 min to measure their cloacal temperature. This simple handling triggered a rise in their core temperatures from 41.5+/-0.6 degrees C at minute 0 to 43.5+/-0.5 degrees C at minute 16. This increase in body temperature occurred with no obvious motor load from the eiders, but was facilitated by peripheral vasoconstriction and, moreover, was blocked significantly by salicylate, suggesting that the increase in temperature was due to fever. After 10 days of similar handling, the mean fever-like responses displayed by the ducks was significantly lower than their responses of day one, showing a habituation to the emotional stimulation. The eider's heart rate was measured continuously before, during and for a 10-min session following a 1-min handling period. Results showed that the eiders displayed a tachycardia during handling and for 2-3 min posthandling. Such tachycardia is another sign of emotion in animals [Am J Psychol 39 (1927) 106]. Our study showed therefore that eider ducks are prone to emotions and, when emotionally stressed, will display a fever-like response and a tachycardia. Our results on ducks are similar to responses obtained from studies on more terrestrial birds in similar conditions (e.g., chicken [Physiol Behav 69 (2000) 541]), but are in opposition to the bradycardia and the observed decreases in temperature [Hvalradets Skr 22 (1940) 1; Acta Physiol Scand 46 (1959) 231] of birds forcibly submerged.