Collective animal behaviour through time

Collective behaviours such as flocking in birds or decision making in colonial insects are some of the most intriguing behavioral phenomena in the animal kingdom. This fascination coupled with advancing technologies has allowed scientists to make ever more refined investigations into the mechanisms and functional value of such behaviours. But, as is often the case with behaviour, this work has generally only been able to focus on snapshots of collective behaviour. This static perspective has hindered our ability to focus on other key questions relating to collective behaviour: how does development and natural selection shape the patterns of mechanisms of such fascinating behaviours? Such 'time-depth' perspectives will help offer insight into how responsive collective behaviours may be to external environmental influence throughout animals lives and whether there are certain pathways of evolutionary least resistance in the mechanisms underlying these behaviours. Experimental and analytical methods for studying collective behaviour, the development of behaviour and evolutionary processes are all well established within each of their fields; our goal here is to facilitate the cross-fertilisation of methodologies and ideas for the benefit of both those already working collective behaviour and those who can apply their expertise in development and evolution to novel questions in collective behaviour. 

Aging is universal amongst vertebrates. The enhanced experience and physical deterioration that come with age can influence how individuals engage with their social worlds. On the flipside, social processes can themselves influence the pace at which individuals age, ultimately impacting on their longevity and ability to reproduce. Our ability to understand the mechanistic and functional drivers of social behaviour is thus fundamentally tied to our understanding of how social behaviour changes across the lifespan. Using data from a long-term fieldsite of macaque monkeys whose individual survival is linked to their social connections to other members of their group, Dr Brent shows how affiliative social interactions change across adulthood – from prime-aged to older adults. Adult females continue to engage with their social worlds as they age but narrow their networks to have a smaller number of partners. Scaling up to higher-level network properties, Dr Brent tests if network narrowing has knock on effects for how indirectly connected older individuals are compared to their younger counterparts, and whether demographic shifts in the age of group members predicts global network properties, eg, are ‘older’ networks more or less connected compared to ‘younger’ networks. Efforts across taxa to quantify changes in sociality as individuals develop and age will help move us towards a more holistic understanding of the causes and consequences of social behaviours. 

Mechanical self-assembly is used by several social insect species to quickly build, out of their own bodies, temporary structures that can serve as shelter, scaffolding, bridges, and even life rafts. For over 50 years, these structures have fascinated naturalists and inspired applications in engineering. Yet, their functional mechanisms and their proximate drivers are still poorly understood. Fortunately, recent technical developments imported from engineering and material sciences have started to uncover the construction principles of these – literally – living architectures. During this talk, Dr Garnier will present recent findings across several social insect species that illustrate the behavioral processes that allow these structures to emerge, develop, adapt, and fade away in response to the needs of the colony and the variable environmental conditions they are subjected to. Dr Garnier will also discuss how these results fit into our general understanding of biological self-assembly, for instance in embryology, and how they can impact areas in engineering interested in the design of complex systems for hard-to-predict and noisy environments.

Collective behaviour is, fundamentally, a response to ecological drivers. For example, animals might be more coordinated and cohesive in their movements when predation risk is higher. However, how animals collectives respond to ecological challenges is likely to reflect not only current conditions, but also individuals' prior experiences. At present, the relative contributions of different temporal processes—individual development, changes in the social environment, and changes in ecological conditions-contribute to the expression of collective behaviours is largely unexplored. One reason is that studies face significant challenges arising from mismatching timescales, where processes such as demographic change take places on completely different timescales to the collective behaviours that they affect. Dr Farine will discuss examples of mismatching timescales, explain the methodological challenges that these raise, and illustrate the conceptual challenges arising from mismatching timescales by drawing from data on wild vulturine guineafowl. By explicitly tackling the challenge of mismatching timescales, Dr Farine hopes to provide some foundations for studying collective behaviour through the lens of development and evolution.

The structure of individuals’ social groups can be an important driver of variation in components of individuals’ fitness. Yet processes that drive variation in social group structure and its impact on fitness -ie, social selection- are not well- described. The genotypic composition of social groups and how it affects individuals’ fitness -ie, indirect genetic effects (IGEs)- is thought to be an important driver of variation in social selection; subsequently, studying the quantitative genetic basis of social group structure and its effects on fitness is necessary for understanding how groups both generate and respond to social selection. Two ways that the genotypic composition of social groups and IGEs can impact social selection is via frequency-dependent selection, and selection on individuals’ direct and indirect social interactions (ie, social network position). Using replicate genotypes of Drosophila melanogaster flies, the researchers manipulated the genotypic composition of social groups, and measured social network positions and multiple components of fitness for individuals within these groups. They found positive frequency-dependent selection operating on measures of females’ fitness, and this frequency-dependent selection varied with indirect genetic effects of social groupmates. Additionally, they found selection operating on measures of individuals’ social network positions, and this selection also varied depending on indirect genetic effects. These findings suggest variation in social selection can be driven by variation in the social context individuals experience. Because social context has a quantitative genetic basis, these findings also suggest social context-dependent social selection provides a mechanism for the adaptive maintenance of social group structure.