DISSERTATION RESEARCH: The functional basis of whole-organism trade-offs between locomotor economy and physical competitive ability

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This study will examine the characteristics of limbs, muscles and physiology of male mice in order to identify the underlying factors leading to a possible trade-off in locomotion versus physical competition. Locomotion and physical competition are critically important activities for most species. However, anatomical and physiological traits that improve performance in either of these behaviors may impair performance in the other. In socially dominant male house mice, those with greater ability to gain and control territories containing females do so at the cost of less efficient locomotion. This trade-off is likely associated with specific anatomical and physiological traits. The results of this study will increase understanding of animal function and conflicting evolutionary pressures. Additionally, this study will be involved in several public engagement projects, including a science lecture series at correctional institutions in Utah, informal science communications events at the Natural History Museum of Utah, and other programs that bring locally-relevant science to Utah residents. This project will also provide research, presentation, and outreach opportunities for undergraduate students.This research will investigate underlying factors that influence locomotor economy and physical competitive performance by comparing the following traits in dominant versus non-dominant male mice: 1) skeletal proportions and anatomical mechanical advantages, 2) muscle mass distribution of the trunk and limb muscles, and 3) muscle fiber types of the proximal and distal forelimb and hindlimb using antibody-based histochemistry. These data will be combined with previously collected data on competitive ability in semi-natural enclosures and locomotor economy using open-flow respirometry in a fully enclosed treadmill. Together, these data will allow the identification of which traits at what levels of biological organization underlie the locomotion-competition trade-off. Additionally, because traits that confer the greatest advantage during male-male contests are also typically those that are the most sexually dimorphic, the same hypotheses for differences between dominant and non-dominant males will be applied to male-female differences. This research will help to answer long-standing, unanswered questions at the intersection of natural and sexual selection.