Data from: Exercise changes behaviour

1. Exercise, which may be defined as bodily movement produced by the
contraction of skeletal muscle and which increases energy expenditure
above basal levels, is essential for fitness-related activities such as
foraging, migration, and dispersal. The frequency with which individuals
engage in exercise depends on a range of intrinsic and environmental
factors. Exercise itself can modify behaviour by inducing endocrine
changes and by a training effect that increases physiological capacities.
2. Here we test the hypothesis that exercise changes behaviour, and that
there is positive feedback so that performing exercise increases the
likelihood of performing exercise-related behaviours. 3. We show that
there was a training effect that improved sustained swimming performance
of mosquitofish (Gambusia holbrooki) exposed to chronic exercise in
flowing water for four weeks compared to sedentary controls. Exercised
fish also became bolder and were quicker to leave a refuge, showed an
increasing tendency to explore unfamiliar environments, and were more
aggressive than sedentary fish. These physiological and behavioural
changes reverted back to control levels when exercised fish assumed a
sedentary lifestyle again. 4. We used the calcium channel blocker
nifedipine to decrease swimming performance of exercised fish to control
levels, which allowed us to determine whether increased locomotor capacity
per se influences behaviour. We show that reducing the swimming
performance of exercised fish also reduced exploration and aggression, but
it did not affect the latency to leave a refuge (boldness). 5. Our data
show that behavioural phenotypes are not fixed. Exercise changes behaviour
and may thereby alter interactions between individuals and dispersal.
Environmental changes that demand increased levels of exercise induce
behavioural responses that are likely to increase the success of
individuals under these changed conditions.