Predicting the rate of oxygen consumption from heart rate in barnacle geese Branta leucopsis: effects of captivity and annual changes in body condition

Quantifying a relationship between heart rate (f(H)) and rate of oxygen consumption ((V) over dot(O2)) allows the estimation of (V) over dot(O2) from f(H) recordings in free-ranging birds. It has been proposed that this relationship may vary throughout an animal's annual cycle, due to changes in physiological status. Barnacle geese, Branta leucopsis, provide an ideal model to test this hypothesis, as they exhibit significant intra-annual variability in body mass, body composition and abdominal temperature, even in captivity. Heart rate data loggers were implanted in 14 captive barnacle geese, and at six points in the year the relationship between f(H) and (V) over dot(O2) was determined. The f(H)/(V) over dot(O2) relationship was also determined in seven moulting wild barnacle geese to examine whether relationships from captive animals might be applicable to wild animals. In captive barnacle geese, the f(H)/(V) over dot(O2) relationship was significantly different only between two out of the six periods when the relationship was determined (late September-early October and November). Accounting for changes in physiological parameters such as body mass, body composition and abdominal temperature did not eliminate this difference. The relationship between f(H) and (V) over dot(O2) obtained from wild geese was significantly different from all of the relationships derived from the captive geese, suggesting that it is not possible to apply calibrations from captive birds to wild geese. However, the similarity of the f(H) and (V) over dot(O2) relationship derived during moult in the captive geese to those during the remainder of the annual cycle implies it is not unreasonable to assume that the relationship between f(H)/(V) over dot(O2) during moult in the wild geese is indicative of the relationship throughout the remainder of the annual cycle.