Exploring the intersection between animal personality and sociality

A topic of growing interest in behavioral ecology centers around the causes and consequences of animal personality - defined as consistent interindividual differences in behavior. Although much work has focused on examining the relationships between an individual’s personality and its fitness, limited knowledge exists regarding how variation in personality is maintained or how the personalities of competitors and actual or potential mates may play into this. Furthermore, few studies have examined how other aspects of an individual’s social environment (e.g. competition levels) might influence relationships between focal personality and fitness, or how the combined personalities of individuals in a group might affect emergent group properties. A main objective of this thesis was to explore how the relationship between focal personality and reproductive performance is modulated by the social environment. In doing so, I aimed to elucidate potential mechanisms that help maintain variation in personality within populations. I progressed from examining the individual level consequences of personality to investigating the effects of group personality composition on emergent group dynamics which, while not examined here, could promote differential fitness between groups.
My thesis demonstrates the potential for an individual’s social environment to interact with its personality to affect reproductive performance. In great tits, I found evidence to suggest that the species composition, but not the conspecific personality composition, of birds breeding in the vicinity of a focal bird, modulated the relationship between focal personality and reproductive performance. Males with different personality types became increasingly similar in the proportion of their clutch fledged with increasing ratios of blue tit to great tit neighbors, suggesting that relaxing the amount of intra- versus interspecific competition led males to converge in reproductive performance. It appears that heterogeneity in an individual’s social environment might influence selection on exploration behavior, but that it is not sufficient in itself to maintain interindividual variation in this behavioral trait. In female-biased red junglefowl groups, I found that slower-exploring males mated with more females when their competitors were faster-exploring, on average, and vice versa. Furthermore, in female-biased groups, the proportion of matings attained by faster-exploring males rose with increasing proportions of slower-exploring males in a group, suggesting negative frequency dependent sexual selection may help maintain interindividual variation in exploration. Lastly, I found that group personality composition in red junglefowl may affect the mean number of aggressive, affiliative, and sexual harassment interactions occurring within the group, as well as the social network structure of these interactions, particularly network density. Understanding the factors that influence network structure are important for our knowledge of processes like disease transmission and information flow, and future work should examine how such emergent group properties might impact group level fitness.
In conclusion, this thesis improves our understanding of the consequences and maintenance of animal personality. It expands upon past work looking at the reproductive consequences of a focal individual’s personality to examine how the social environment may work to shape the relationships between focal personality and reproductive performance. Future work should examine the broader ecological and evolutionary consequences of my results and how individual and group level outcomes might influence population and community dynamics.

Keywords: Ornithology
Sexual Selection
Behavioural ecology
Animal personality
Group phenotypic composition
Sociality
Advisor: Sheldon, B
Pizzari, T
Cole, E