Abstract
Living in groups has various advantages and disadvantages for group members. We investigated the fitness consequences of early social connectivity (normalized Freeman degrees based on nearest neighbour data), physiology (levels of excreted corticosterone metabolites assayed from droppings), and agonistic interactions in a group of free-ranging greylag geese (Anseranser). Forty-four greylag geese below 3 years of age were observed in three different seasonal phases: during the re-aggregation of the flock in autumn, at the end of the winter and during the forthcoming breeding season. We show that corticosterone metabolite levels and initiated and received aggression increased with increasing social connectivity. Individuals had higher connectivity scores in the winter flock than during the mating and breeding seasons. One-year old juveniles were more connected than 2- and 3-year old individuals. In addition, we examined the link between social connectivity during early development and reproductive success several years later. We found that birds with greater connectivity early in life attempted to breed at a younger age. Furthermore, successful breeders with higher early connectivity scores had higher numbers of fledged goslings. Our results show that social context in early life stages may have long-term effects on individual fitness.
Highlights
The adaptive value of group living has long been documented, especially with emphasis on the costs and benefits involved[1]
We investigated the interplay between early social connectivity, calculated as centrality based on the number of nearest neighbours in a social network analysis (SNA), and physiology, expressed as levels of excreted corticosterone metabolites (CM), in 1-year old juveniles and immature (2- and 3-year old) greylag geese in a non-migratory and free-roaming flock in Upper Austria
The interaction between season and age showed a high connectivity during the winter and the mating season in juveniles, while social connectivity gradually decreased in 2- and 3-year old individuals from winter throughout the mating and breeding season (Fig. 3)
Summary
The adaptive value of group living has long been documented, especially with emphasis on the costs and benefits involved[1]. Zebra finches exposed to corticosterone early in life were shown to have weaker associations to their parents, but instead higher numbers of association with other flock mates later in life[19] Both studies highlight that the structure of social groups, as well as the position of an individual within the social group, which was assessed using www.nature.com/scientificreports/. We investigated the interplay between early social connectivity, calculated as centrality based on the number of nearest neighbours in a SNA, and physiology, expressed as levels of excreted corticosterone metabolites (CM), in 1-year old juveniles and immature (2- and 3-year old) greylag geese in a non-migratory and free-roaming flock in Upper Austria. With regard to future reproductive success, we expected to find higher numbers of fledged goslings from individuals that showed high early social connectivity, probably due to access to high quality nesting and foraging sites
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