Delayed costs of growth and compensatory growth rates

1. Many studies recognize that growth carries with it a mortality risk that can influence an animal's growth rate. 2. Data suggest that these costs of growth act over a range of time-scales, from instantaneous to an animal's lifetime. 3. Models of adaptive growth rate have not addressed the issue of differing time-scales over which the costs of growth act. Here, we develop an adaptive growth model in which the costs of growth are delayed for a period of time, to assess optimal growth strategies in relation to delays in growth costs. 4. The optimal growth rates are calculated assuming one of two possible fitness measures: the reproductive rate, R-0 and the intrinsic population growth rate, r. 5. It is shown that if the costs of growth are felt only after maturity, then growth compensation can be an adaptive strategy, even in an unchanging environment. 6. Compensatory growth is predicted only when R-0 is the relevant fitness measure, implying that this mechanism of compensatory growth is sensitive to the processes of population regulation. 7. The effect of time-delayed costs for other life-history problems is discussed in light of these results.