Secondary sexual ornaments as signals: the handicap approach and three potential problems

ABSTRACf. Secondary sexual ornaments as signals:77te handicap approach and three potential problems.Secondary sexual ornaments have recently been discussed in the context of biological signals, and the handicap principle has been suggested as a model explaining their evolution. The handicap principle predicts that at equilibrium, sexual ornaments will be honest signals of the male's quality. This is because the cost of ornaments to a potential cheater (a low quality male) will be greater than to an honest signaler (a high quality male), to an extent that makes cheating maladaptive. Accordingly, the cost of the ornament (the handicap) should be related to the quality it reveals. In the following, I discuss three problems with the handicap approach: i) It is difficult to determine the cost of the handicap and the quality it reveals. Nevertheless, I suggest that it is feasible and is worth doing. ii) It is not clear whether phylogenetic data can be used to distinguish between the handicap model and the sensory exploitation model. I suggest that it can be used only under restricted conditions. ill) Cheating (dishonest signalling) seems to contradict the handicap model. I will try to show, however, that some forms of cheating can be explained by the handicap model.