Born to be bold? Personality traits and reproductive performance in Magellanic penguins (Spheniscus magellanicus)

Abstract

Personality differences in animals are defined as consistent behavioral variation among individuals and are known to influencefitness. However, the mechanisms by which personality traits affect fitness remain largely underexplored. In this study,we assessed intra-annualboldness in Magellanic penguins (Spheniscus magellanicus) from a breeding colony on Isla Quiroga,Argentina, using a novel object test during incubation and chick-rearing.We estimated its repeatability, examined whether boldnesscorrelated with reproductive performance, and explored how this relationship varied across years with differing resourceavailability and environmental conditions. Boldness remained consistent over the breeding season, and we found a negative associationbetween male boldness and reproductive success, as bolder males fledged fewer chicks. In addition, although boldnesswas not associated with mate choice, pairs with similar boldness exhibited intermediate reproductive success (approximately onefledgling from two eggs). Overall, our findings indicate that variation in boldness behavior may play a role in shaping reproductivesuccess in this species.