The metabolic rates associated with resting, and with the performance of agonistic, submissive and digging behaviours in the cichlid ®sh Neolamprologus pulcher (Pisces: Cichlidae)

We measured the metabolic rates as a direct estimate of energy expenditure of individual Neolamprologus pulcher, a cooperatively breeding cichlid ®sh, when resting and when performing agonistic, submissive or digging behaviours in a respirometer. Standard and routine metabolic rates increased linearly with body mass (range 0.9±8.4 g) when plotted on a doubly logarithmic scale (linear regression equations: standard metabolic rate: log individual oxygen consumption rate ˆ 0.65 + 0.86 log body mass; routine metabolic rate: log individual oxygen consumption rate ˆ 0.75 + 0.86 log body mass). Routine metabolic rates were, on average, 30% higher than standard metabolic rates. Submissive and agonistic behaviours raised routine metabolic rates by factors of 3.3 and 3.9, respectively. Digging resulted in a 6.1-fold increase of routine metabolic rates. Di€erences in metabolic rates between active and resting rates were statistically signi®cant. However, those between the three behaviours were not. Mean opercular beat frequencies correlated signi®cantly with routine metabolic rates and with metabolic rates when performing speci®c behaviours, which o€ers methodological prospects for ®eld measurements. In N. pulcher, the high energy expenditure for submissive behaviour may indicate that this is a reliable signal. The considerable energy expenditure involved in territory defence suggests that these costs should be considered in addition to risk in cost-bene®t analyses. This is the ®rst study in which the energy expenditures of speci®c social and territory maintenance behaviours of individual ®sh were measured directly by respirometry and within the usual social setting of the ®sh.