How costly is the honest signaling of need?

ESS models of biological signaling have shown that costly signals can provide honest information. In the context of parent-offspring conflict over the allocation of resources by parents to their young, the theory explains costly offspring solicitation behavior as an accurate signal of offspring need to parents who cannot assess offspring condition directly. In this paper, we provide a simple but general characterization of the honest signaling of need in models of parent-offspring conflict: the offspring's signaling cost is proportional to the parent's fitness loss from satisfying the offspring's resource requirement. The factor of proportionality is given by a measure of the extent of parent-offspring conflict that depends only on coefficients of relatedness. These results hold for interbrood conflict with uniparental investment even if the relationship between offspring condition and resource requirement is not monotonic, and extend to cases of biparental care, uncertainty concerning the parent's condition, and intra-brood conflict. Copyright 1999 Academic Press.