Animals move continually, interacting with others, foraging for food and searching for new territory, but what determines the speed at which they go about their everyday business? ‘Often, animals do not reach their maximal locomotor capacity when moving under undisturbed conditions’, say Frank Seebacher and colleagues from the University of Sydney, Australia. Having discussed potential mechanisms that may determine the voluntary speed at which animals move, including the role of muscle efficiency and the impact of temperature on muscle contraction, Seebacher and his team monitored the movements of fish swimming at 18, 24 and 30°C in a shallow featureless tank before analysing their movements during the first and tenth minute to determine how their voluntary speed varied with their familiarity with a location. In addition, the team measured the fish's top swimming speed and their metabolic rate in a bid to identify the factors that determine the fish's voluntary speed.
The team found that the fish increased their voluntary speed when exploring novel environments regardless of the increased metabolic cost that this incurred. However, when they were familiar with their surroundings and at the temperature that they normally inhabit, their energy expenditure did not increase. ‘The implications of these data are that the energetic costs of exploring and dispersal into novel environments is relatively greater than movement within familiar home ranges’, says the team, who suspect that the urge to explore novel settings overrides the fish's determination to conserve energy, making exploration a costly prospect for fish that fail to locate new resources or encounter predators.
