Sociality and reproductive strategies in ground-dwelling squirrels: effects of infection on reproduction and sperm competition

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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 cooperative food searching, they also incur increased costs, such as more competition for food or mates and greater exposure to diseases and parasites. My research program focuses on understanding the evolution of sociality by examining these costs and benefits. One cost, increased competition for mates, can result in increased sexual selection. First described by Darwin, sexual selection includes one sex directly competing to gain access to the other or mate choice of one sex for the other. 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 male-male competition can also occur within the reproductive tract of the female. Thus we seek to understand not only external features resulting from sexual selection (e.g. peacock's tail or large antlers), but also internal (such as the speed of sperm). As copulations alone do not ensure fertilization we must look beyond the behaviour of the animal to the behaviour of his sperm. We will examine specific differences in the morphology and functioning of sperm, as well as the response of individuals to pathogens and parasites and effects on their fertility. Understanding differences in sperm morphology 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 and sexual selection in solitary and social, free-ranging ground squirrels using a combination of behavioural, molecular, and endocrine techniques. Results of our research will have both theoretical and applied implications to evolutionary biology and epidemiology.