Perturbation, Social Rewiring, and Population Dynamics in Animal Societies

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Many animal species are at risk of extinction in the wild and understanding the threats to these populations is essential to ensure their conservation. In many species, social relationships are essential for individual survival and the strength and quality of an individuals' social relationships can predict their reproductive success. For long-lived animals, the death of social partners (perturbation) represents a major upheaval that can have long-lasting negative effects on survival. We thus expect individuals to rewire and adjust their social relationships after the loss of a social partner to mitigate the negative effects of partner loss. Social rewiring strategies are likely to be crucial in determining the resilience of long-lived animal populations to environmental change. Social rewiring strategies that are individually adaptive (e.g. that improve individual survival) will alter the global social network structure, which may have positive or negative consequences for population resilience. For example, the degree of social connectivity within a population can determine the population's vulnerability to decline or even extinction, for example, because of its susceptibility to a disease outbreak. We predict that this system of feedbacks (social network structure affects survival/reproduction and vice versa) will drive population dynamics, which in shrinking populations may hasten or delay population decline. Currently however, we have little understanding of the rewiring strategies that animals use in wild populations or their implications for population resilience. This project will capitalize on the unique opportunity provided by the long-term monitoring of a population of highly social resident killer whales in the coastal waters off Washington State, USA, and British Columbia, Canada, for which we have access to over 45 years of detailed demographic and social data on all individuals. The project will quantify the rewiring strategies that individuals use following the death of a social partner and determine how individuals regulate their existing relationships and form new ones. Moreover, using the long-term data the project will determine the consequences of individual rewiring strategies for population trajectories and feedbacks between social structure and demography. Outputs of this work will provide a new fundamental understanding of the link between population dynamics and social behaviour and will improve our ability to forecast population trajectories and design conservation interventions in social species.