THE USE OF HEART-RATE TO ESTIMATE OXYGEN-CONSUMPTION OF FREE-RANGING BLACK-BROWED ALBATROSSES DIOMEDEA MELANOPHRYS

Heart rates (fH) and rates of oxygen consumption (Vo(2)) were measured in eight black-browed albatrosses (Diomedea melanophrys) when walking on a treadmill, with the aim of using fH to predict Vo(2), in free-ra nging albatrosses. The resulting relationship between the variables wa s: Vo(2) (ml min(-1)) = [0.0157 fH (beats min(-1)](1.60), r(2)= 0.80, P<0.001. In addition to the calibration procedure, six of the albatros ses were injected with doubly labelled water (DLW), and fH and Vo(2) w ere monitored continuously over a 3 day period while the birds were he ld in a respirometer. During the 3 day period, the birds were walked f or up to 3-4 h day(-1) in bouts lasting approximately 0.5 h. The heart rate data were used to estimate the metabolic rates of these birds us ing the above regression. Estimates of metabolic rate derived from fH, DLW and respirometry did not differ (ANOVA; P=0.94), primarily becaus e of the variance between individual birds. There was also no signific ant difference between the different estimates obtained from the diffe rent equations used to calculate energy expenditure from the DLW techn ique (ANOVA; P=0.95). Mean estimates of Vo(2) from fH under active and inactive conditions differed from measured values of Vo(2) by -5.9 % and -1.7 % respectively. In addition, the estimates of Tie, from fH at different walking speeds did not differ significantly from the measur ed values. It appears that, in the black-browed albatross, fH is as go od a predictor of the mean metabolic rate of free-ranging birds as DLW or time-energy budgets combined with either respirometry or DLW. Howe ver, the method should be applied to as many individuals and as many i nstances of a particular behaviour as possible. The heart rate techniq ue offers potential for much more detailed analyses of the daily energ y budgets of these birds, and over much longer periods, than has previ ously been possible.