How does an individual's optimal behaviour depend on its quality? An analysis based on relative ability

We analyse how an organism's behaviour is predicted to depend on its quality when there is a trade-off between survival and reproduction and fitness can be written in the form of a product of these two factors. The analysis is general, but we focus on two specific cases: the level of display of a male trying to attract a female and the level of effort of a parent caring for young. In each case, an increase in the level of behaviour increases the...