Male personality and female spawning consistency in a goby with exclusive male care

Consistent inter-individual behavioral differences in animals, or animal personalities, are increasingly recognized as an important component of sexual selection. Despite growing evidence for personality-mediated effects on reproductive success in species with biparental care, the link between personality and intrasexual competition or mate choice in species with uniparental care remains largely unexplored. Here, the non-caring sex in particular should seek partners with personality traits that promise high quality care. Therefore, we investigated effects of male personality in the common goby, a well-established model species for sexual selection under exclusive male care. Using competitive trials, we investigated how personality affects male ability to monopolize either of two central reproductive resources, nesting sites (male-male competition) and ready-to-spawn females (female choice). Personalities were scored in a feeding context and thus independent of reproduction. We found that slow-feeding individuals better succeeded in monopolizing nests, but that female spawning decisions were independent of the foraging personality of two male competitors. Instead, females showed a remarkably consistent between-female spawning preference for slightly heavier males and males with more elaborate nests. Our findings indicate that fitness benefits of the male personality type only materialize via male-male competition in environments where nesting sites are a limiting resource, whereas female choice favors large males with elaborate nests independent of male personality. Animal personality can strongly affect reproductive success in species with parental care. We studied this link in the common goby, a fish where males build nests and solely take care of the brood until hatching. Hence, females should choose a male whose personality traits promise high quality care. We scored male personalities and conducted nest-competition and mate-choice trials. We found that male personality had an effect on nest monopolization, but not on female mating preferences. Instead, females agreed remarkably well in their mating decisions and consistently favored large males with elaborate nests. Our results show that male personality is important for nest allocation, which is crucial in environments where nesting sites are rare.