Oxygen consumption during crowing by roosters: talk is cheap

The energetic cost of signalling may be important in maintaining the honesty of the signal, yet it is rarely measured directly. Oxygen consumption during crowing by roosters, Gallus gallus domesticus, was measured in a closed-circuit indirect calorimeter. Although there was a positive relationship between crowing and O 2 consumption, roosters consumed only 0·005 ml/g/h for each vocalization. Thus at the average crowing rate, O 2 consumption rate would be 15% above standing, which is less than the cost of low-level activities such as feeding, drinking and preening, and over 10 times less than the maximum sustainable metabolic rate. These results contrast with previous reports of high energy consumption during calling in insects and frogs, which approach or exceed maximal levels. Other costs, such as predation and social retaliation, are probably more important than energetic costs in maintaining crowing as an honest signal.