The Eastern migratory monarch butterfly has declined in the last few decades. One potential driver of the decline is loss of milkweed from cropland habitats in the Midwest. In addition to losing much of their breeding habitat, monarchs have also shifted away from laying eggs on milkweeds in crop fields and now rely more heavily on milkweeds growing in perennial grasslands. In this talk we will provide an overview of several recent experiments we conducted to examine the implications of monarchs' habitat shift toward grasslands and begin to explore habitat management actions that could be taken in light of it.
Results/Conclusions
We found predation pressure on monarch eggs and larvae in grasslands can be much higher than that in crop fields. Furthermore, lab trials and field observations reveal that arthropod predators of monarchs are much more diverse than previously recognized. We also found evidence that grassland disturbance, which we tested in the form of strategically-timed mowing, produces regenerating milkweed stems that are used heavily for oviposition and contain less predators. Taken together, this evidence suggests targeted grassland disturbance should be explored as a tool to enhance monarch butterfly breeding habitat.