Testing Predictions of Optimal Migration Theory in Migratory Bats

Optimal migration theory is a framework used to evaluate trade-offs associated with migratory strategies. Two strategies frequently considered by are time minimizing, whereby completed as quickly possible, and energy energetically efficiently possible. Despite extensive literature dedicated generating analytical predictions about these strategies, identifying appropriate study systems empirically test difficult. Theoretical that compare qualitative, empirical tests require both time-minimizers energy-minimizers present in the same population; spring migrating silver-haired ( Lasionycteris noctivagans ) hoary bats Lasiurus cinereus provide such system. As species mate fall, spring-migrating males thought be while females benefit from early arrival summering grounds, time-minimizers. Thermoregulatory expression also varies between during migration, female of use torpor bats, which implant embryos earlier, avoid would delay pregnancy. Based on optimal theory, we predicted have increased fuel loads relative difference male greater than bats. We stopover foraging proclivity and/or assimilate nutrients at rate males. then tested our using quantitative magnetic resonance measure load, ? 13 C isotope breath signature analysis assess foraging, C–labeled glycine an indicator nutrient assimilation rate. load were supported, but field observations did not support refueling mechanisms, alternatively suggested reliance via carry-over effects. This research first validate prediction system minimizers uses novel methodological approaches uncover underlying mechanisms use.