Energetics in the Atlantic bottlenose dolphin, Tursiops truncatus Montagu
Various aspects of energetics of the Atlantic bottlenose dolphin, Tursiops truncatus Montagu, were investigated, including the relationship between ventilation rate and behaviour, the structure of the breath, basal metabolic rate, and the cost of echolocation. An ethogram was defined through observation of a sub-group of seven dolphins, which proved to be representative for dolphins in captivity. Ventilation rates for the behaviours within the ethogram were measured using a stopwatch, and analysis of spoken and filmed commentaries, on the behaviour of 36 dolphins at five study sites. Ventilation rate was found to vary significantly with behaviour, and was used to estimate the relative costs for different behaviours. All the behaviours were assumed to be aerobic as there was no correlation between consecutive apnoeic periods, and there were no "carry-over" effects when dolphins changed behaviour. Swimming at approximately 1.5 m s-1 and 2 m -1s, incurred similar ventilation rates, and presumably costs, to stationary resting. Ventilation rate increased as speed increased, or when the dolphins swam at the surface. Dolphins spent the majority of time for which they were observed in the behaviours which incurred the lowest ventilation rates. Six ventilatory parameters were measured in 29 dolphins. These included expiration and inspiration duration, the time for which the blowhole was open, and the time spent at the surface. Mean breath duration (expiration + inspiration) was 0.860.16 s (n=2762). The duration of both expiration and inspiration could be varied, although inspiration was more flexible than expiration. Expiration time could be increased by reducing inspiration time or by extending the time the blowhole was open. Inspiration time had a significant influence on the time the blowhole was open and the time spent at the surface.