Measurement of maximum oxygen consumption in guinea fowl Numida meleagris indicates that birds and mammals display a similar diversity of aerobic scopes during running

Judgement of exercise performance in birds has been hampered by a paucity of data on maximal aerobic capacity. We measured the maximal rate of oxygen consumption ((V)over dotO(2,max)) in running. guinea fowl Numida meleagris, a bird that has been used in several previous studies of avian running. Mean (V)over dotO(2,max) during. level treadmill running was 97.5 +/- 3.7 mL O-2 kg(-1) min(-1) (mean +/- SEM, N = 5). (V)over dotO(2,max) was on average 6% higher when the birds ran uphill compared with the value during level running (paired t-test, P = 0.041, N = 5). The mean basal rate of oxygen consumption ((V)over dotO(2,max)) of the same individuals was 7.9 +/- 0.5 mL O-2 kg(-1) min(-1). Mean factorial aerobic scope based on individually measured values of (V)over dotO2, max and (V)over dotO(2,bmr) was 13.2 +/- 0.6 (mean +/- SEM, N = 5). This value was considerably lower than the factorial aerobic scope previously measured during running in Rhea americana, a large flightless ratite. The difference in factorial scope between these two running birds likely reflects the effects of body size as well as size-independent differences in the ability to deliver and use oxygen. These data confirm a previous prediction that birds have a diversity of factorial aerobic scopes similar to that exhibited by mammals.