Social context modulates how the winner effect restructures territorial behaviour in free-living woodpeckers

Abstract

Animal interactions such as competition are mediated by complex social strategies, which consist of behaviours and cognitive mechanisms that guide their production. As a result, behaviour is highly flexible. This poses a challenge to understanding how competition plays out in natural systems, because the course of a contest can essentially be rewritten by prior experience and/or changes in social context. Here we addressed this gap by studying how both of these factors interact to reconfigure competitive strategies used in territorial defence by a wild bird. After experimentally inducing the winner effect, a cognitive-behavioural phenomenon in which winning a contest increases the probability of winning again in the future, we found that male red-bellied woodpeckers, Melanerpes carolinus, adopted a new social strategy marked by more flexible transitions between different aggressive displays, as well as increasing overall aggressive output. However, this effect was mitigated by the arrival of the female social mate; in response to this momentary shift in social context, males decreased their use of territorial drum displays and became less likely to move around the territory or switch display modes during competition. In other words, the winner effect increased spatiotemporal diversity of territorial strategies, such that males frequently changed their location and display output. A female's arrival, however, reversed this effect. More specifically, males tended to revert to advertisement and social vocalizations on female arrival, which suggests that the need to attend to the social mate may supersede the threat of territorial intrusion. This is consistent with a model in which competitive outcomes are impacted by the interactive effects of an individual's past experiences and shifts in present-day social context, which may allow monogamous animals to effectively manage the competing demands of driving off intruders and attending to the social mate.