Opposite-sex associations are linked with annual fitness, but sociality is stable over lifetime

Abstract

Animal sociality, an individuals propensity to association with others, has consequences for fitness, and particularly mate choice. For example, directly, by increasing the pool of prospective partners, and indirectly through increased survival. Individuals benefit from both over the short-term as these benefits are associated with mating status and subsequent fecundity, but whether animal sociality also translates into fitness is unknown. Here, we quantified social associations and their link with annual and lifetime fitness, measured as the number of recruits and in de-lifed fitness. We measured this in birds visiting a feeding station over two non-breeding periods, using social network analysis and a multi-generational genetic pedigree. We find high individual repeatability in sociality. We found that individuals with an average sociality had the highest fitness, and that birds with more opposite-sex associates had higher fitness, but this did not translate to improved lifetime fitness. For lifetime fitness, we found evidence for stabilizing selection on between sex sociality measures, suggesting that such benefits are only short-lived in a wild population.

Adaptive significance of affiliative behaviour differs between sexes in a wild reptile population

“…This is probably a case of increased mating opportunity relative to the number of females that are social associates [ 53 , 54 ]. Interestingly, this echoes recent findings that house sparrows ( Passer domesticus ) with more opposite-sex associates gain within-year fitness advantages [ 55 ]. However, this pattern appeared to exist for both sexes in sparrows, whereas only male dragons appeared to benefit from these particular social traits.…”

Indirect genetic effects improve female extra-pair heritability estimates

“…We have monitored the sedentary and closed population of house sparrow Passer domesticus (hereafter sparrow/s) breeding on Lundy Island in the Bristol Channel, UK (51°10’N, 4°40’W), since 1984 (see Ockendon, Griffith, and Burke 2009; Schroeder et al 2012; Dunning et al 2022). The sparrows on Lundy breed in nest boxes.…”