Information in Scent Signals of Competitive Social Status: The Interface Between Behaviour and Chemistry

Abstract

From an evolutionary viewpoint, signals generally should be reliable or honest (Zahavi, 1987; Johnstone, 1997). Animals can gain a number of advantages from advertising high competitive ability to potential mates and to other competitors, particularly males which often compete strongly for mating opportunities (Andersson, 1994). Animals often prefer high quality mates that will increase the fitness of their offspring, both because of genetic benefits (through good genes or Fisherian selection) and because parents of high competitive ability often provide better resources and protection. Competitors will also gain an advantage if potential challengers withdraw from, or otherwise avoid, aggressive encounters with an opponent of high fighting ability. There is thus strong selection pressure on signallers to advertise high social status and competitive ability to others. However, receivers will only gain an advantage from responding to such signals if these are reliable indicators of the signaller’s competitive ability. Females that mate with low quality males that dishonestly signal high competitive ability will gain no advantage for their offspring, while males that withdraw from agonistic encounters with poorer competitors will be disadvantaged. There is thus strong selection on receivers to respond only to honest signals that are resistant to cheating, and therefore for high quality animals to provide such reliable information in signals as these will be effective in attracting mates and deterring competitors.