Meeting Abstract
A key theory in life-history research predicts the existence of a trade-off between current and future reproductive success. Increases in the cost of each reproductive attempt theoretically reduce future reproductive ability. Additionally, the cost of a single reproductive attempt may shift with body size, altering the relationship between this trade-off. Historically, however, it has been difficult to experimentally quantify these costs in organisms. Squamate reptiles have proved a good model to measure reproductive costs as reduction in locomotor performance is easily quantified. As the burden of reproductive material increases, we predict a corresponding reduction in locomotor performance and thus a greater cost to reproduction. We measured the swimming speed of watersnakes during and immediately after pregnancy to estimate the loss of locomotor imposed by reproduction. Further, we correlated this loss of swimming speed with relative clutch mass (an estimate of reproductive effort) and body length. Female snakes swim slower during pregnancy than after. Increasing the relative clutch mass resulted in slower swimming speeds during pregnancy. Further, shorter individuals showed a greater change in swimming speed suggesting a greater to cost of reproduction for smaller individuals. Lastly, we have demonstrated that additional costs to locomotor ability may be incurred by the dam due to weight loss during pregnancy from carrying the burden of reproductive material.
