Swimming and Diving in Tufted Ducks, Aythya Fuligula, with Particular Reference to Heart Rate and Gas Exchange

In six tufted ducks there was a linear relationship between heart rate and oxygen consumption when swimming at different velocities.Mean oxygen consumption at mean duration of voluntary dives was 3.5 times resting and not significantly different from that at maximum sustainable swimming speed. Contrary to an earlier report (Prange & Schmidt-Nielsen, 1970), leg beat frequency increased with increased swimming speed. Although heart rate at mean dive duration was 51 % higher than the resting value, it was a significant 59 beats min−1 lower than predicted from the heart rate/oxygen consumption relationship obtained during swimming. This relationship is, therefore, of no use for predicting oxygen consumption from heart rate during diving, nor incidentally during transient changes during air breathing. It is concluded that during voluntary diving in tufted ducks there is a balance between the cardiovascular responses to forced submersion (bradycardia, selective vasoconstriction) and to exercise in air (tachycardia and vasodilatation in active muscles), with the bias towards the latter.