Sociality and reproductive tactics in ground-dwelling squirrels: conflict and cooperation

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Why some animals are social and others are not is a major area of research in animal behaviour. Although individuals in groups can benefit from collective detection of predators or helping each other raise offspring, they also incur increased costs, such as more competition for food or mates and the loss of reproductive opportunities. My research program focuses on understanding the evolution of sociality by examining these costs and benefits. In complex animal societies, females usually live with their close kin but these close kin are also their closest competitors. Reproduction in such groups is not equally distributed and success is often determined by dominance or aggression. Less is known about the factors influencing reproductive distribution in egalitarian societies that do not use aggressive means of competing for resources, even when we observe unequal reproductive success. We will test hypotheses related to the factors that influence female reproductive success in a species with what appears to be an egalitarian social system (all adults breed and there is no dominance hierarchy), but where some females wean far more offspring than others. While females may compete for resources, males are predicted to compete for mates via sexual selection. First described by Darwin, sexual selection includes one sex directly competing to gain access to another or mate choice by one sex. Such competition or choice can lead to adaptations including large antlers and brightly coloured feathers. However, if a female mates with more than a single male, then competition can also occur in the reproductive tract of the female. Thus we seek to understand more than just the visible results of sexual selection (e.g. peacock's tail), as copulations alone do not ensure fertilization. We will examine specific differences in the morphology and functioning of sperm and other reproductive structures under different social situations. Understanding differences in sperm form and function among males may be the ultimate key to understanding reproductive success, yet few studies have investigated these differences. We will test critical hypotheses about the evolution of social behaviour, reproduction, and sexual selection in solitary and social, free-ranging ground squirrels, particularly the social African ground squirrel (