Ageing, reproductive value, and the evolution of lifetime fighting behaviour

Abstract

The study of sexual selection has recently been enriched by an explicit life history focus. This lifetime perspective has much to offer the field; however, most existing interdisciplinary exchanges have restricted themselves to the context of mate choice and associated phenomena. The present study explores the consequences of an explicit life history view upon the evolution of male-male contest competition. Key to this view is the fact that fighting typically has lifetime consequences, and thus the costs involved with contests are best considered in lifetime currencies such as residual reproductive value. The rate of contemporary contest cost accrual may vary among contestants due to differences between them in what they 'stand to lose', in terms of future reproductive opportunities. It is also suggested that it may be fruitful to partition key life history parameters into components that are either dependent or independent of future choice of mating strategy. Using a simple simulation, it is demonstrated that the optimum pattern of lifetime contest participation may vary depending upon lifetime variation in 'strategy-independent' components of reproductive value (such as the rate of mortality experienced in contexts unrelated to mating behaviour). In line with previous models of age-specific sexual advertisement, increasing lifetime aggression appears as the most favoured strategy; however, young age aggression is predicted if resource holding potential is expected to decline with age irrespective of prior contest participation. The model is discussed, along with key concepts surrounding the life history viewpoint, in light of prior life history/sexual selection models and the existing empirical data regarding lifetime fighting strategies in the wild. © 2006 The Linnean Society of London.