How are animals with ornaments predicted to compensate for a bad start in life? A dynamic optimization model approach

Summary1 Animals may compensate for a poor start in life by accelerated (‘catch up’) growth if conditions subsequently improve. Although this incurs costs, the occurrence of catch up growth across taxa suggests there are also considerable benefits to it. 2 A state‐dependent, dynamic optimization model was constructed to explore how and under what circumstances individuals are predicted to vary their compensatory resource allocation to soma vs sexual ornaments. 3 In the model, individuals of differing initial state either experienced a constant environment, or one in which initially poor resource availability subsequently improved. Individuals could allocate resources, at each time step, to body growth, somatic maintenance or a sexual ornament. 4 The results showed that resource allocation strategies are sensitive to the fitness return functions used. Consequently, there is a wide range of potential optimal adult phenotypes. 5 Four general patterns emerged. (i) Making specific predictions about compensatory resource allocation is difficult owing to the general lack of information about the shape of the fitness return functions. (ii) Complete compensation in expected fitness (such that a poor start does not reduce future fitness) is likely to occur rarely. (iii) If a sexual ornament is required for mating success, compensating individuals are likely to be smaller in body size than those experiencing a constant environment. (iv) Poor initial resource availability in life tends to delay sexual maturation.