Begging and bleating: the evolution of parent-offspring signalling

The evolution of biological signalling in the face of evolutionary conflict s of interest is an active area of evolutionary ecology, and one to which M aynard Smith has made important contributions. We explore the major theoret ical challenges in the field, concentrating largely on how offspring signal to their parents when there is the potential for parent-offspring conflict . Costly offspring solicitation (begging etc.) has been interpreted in term s of a Zahavi-Grafen honest handicap signal, but this has been challenged o n the grounds of the costs of signalling. We review this controversy and al so explore the issue of pooling versus separating signalling equilibrium. A n alternative explanation for costly begging is that it is due to sibling c ompetition, and we discuss the relationship between these ideas and signall ing models in families with more than one offspring. Finally we consider si gnal uncertainty; how signalling models can be made dynamic, and briefly ho w they may be tested experimentally.