Estimation of the rate of oxygen consumption of the common eider duck (Somateria mollissima), with some measurements of heart rate during voluntary dives

The relationship between heart rate (f(H)) and rate of oxygen consumption ( (V) over dot O-2,) was established for a marine diving bird, the common eld er duck (Somateria mollissima), during steady-state swimming and running ex ercise. Both variables increased exponentially with speed during swimming a nd in a linear fashion during running. Eleven linear regressions of (V) ove r dot O-2, (ml kg(-1) min(-1)) on f(H) (beats min(-1)) were obtained: five by swimming and six by running the birds. The common regression was describ ed by (V) over dot O-2=10.1+0.15f(H) (r(2)=0.46, N=272, P<0.0001). The accu racy of this relationship for predicting mean (V) over dot O-2 was determin ed for a group of six birds by recording f(H) continuously over a 2-day per iod and comparing estimated (V) over dot O-2 obtained using the common regr ession with (i) (V) over dot O-2, estimated using the doubly labelled water technique (DLW) and (ii) (V) over dot O-2 measured using respirometry. A t wo-pool model produced the most accurate estimated db, using DLW. Because o f individual variability within mean values of (V) over dot O-2, estimated using both techniques, there was no significant difference between mean (V) over dot O-2 estimated using f(H) or DLW and measured (V) over dot O-2 val ues (P>0.2), although individual errors were substantially less when f(H) w as used rather than DLW to estimate (V) over dot O-2. Both techniques are, however, only suitable for estimating mean (V) over dot O-2 for a group of animals, not for individuals. Heart rate and behaviour were monitored during a bout of 63 voluntary dives by one female bird in an indoor tank 1.7 m deep. Tachycardia occurred both in anticipation of and following each dive. Heart rate decreased before su bmersion but was above resting values for the whole of the dive cycle. Mean f(H) at mean dive duration was significantly greater than f(H) while swimm ing at maximum sustainable surface speeds. Heart rate was used to estimate mean (V) over dot O-2, during the dive cycle and to predict aerobic dive li mit (ADL) for shallow dives.