Meeting Abstract
Economical locomotion and maintaining social dominance are vital to many speces because of their direct impact on components of fitness. Locomotor economy is thought to be an important performance trait because it directly influences total daily energetic expenditure. For example, reduced locomotor economy and the subsequent higher energetic demand may increase viability costs, such as increased foraging time and exposure to predation, as well as decreased free energy for growth, maintenance, and reproduction. Social dominance is important because it often directly determines reproductive success. In species that fight to determine social dominance, fighting performance may be under strong selection. However, traits that improve either fighting ability or locomotor economy may decrease performance in the other, resulting in a trade-off. We used populations of wild-derived house mice (Mus musculus) in 8-week social competition trials in semi-natural enclosures to directly measure several aspects of male reproductive fitness including social dominance through control of female-occupied territories. In addition, we measured locomotor economy for each male across a range of intermediate speeds using running trials in an enclosed treadmill and open-flow respirometry. Our results indicate that socially dominant male mice have a higher cost of transport (i.e., reduced locomotor economy) than non-dominant males. This relationship was significant for measurements taken both before and after social competition trials. In contrast to the positive correlation between body mass and social dominance in other species, body mass was not predictive of social dominance in our mice, indicating that other physiological, musculoskeletal, or behavioral traits underlie these performance differences. These results are consistent with the hypothesis that there is a trade-off between economical locomotion and fighting ability.
