The eastern migratory population of monarch butterflies has experienced a significant decline since the 1990s. The predominant cause of the decline has been attributed to loss of breeding habitat. Milkweed, the host plant for monarchs, is a prerequisite for breeding habitat. Nearly 2 billion milkweed stems are needed to restore and sustain the eastern population of monarchs in the US. To ensure that habitat restoration efforts are targeted towards areas that are accessible for monarchs, it is necessary to understand the effects of landscape spatial heterogeneity on monarch presence. The objective of this study is to understand how the size of a patch of milkweed and its proximity to other breeding habitat in the surrounding landscape affects whether monarchs will occupy it. To understand the effect of patch size and surrounding habitat on monarch presence and survival, we survey of monarch at 60 sites in Wisconsin that vary in milkweed patch size and in a landscape context within which the patches exist. This research will yield insights on ideal milkweed habitat placement in the landscape.
Results/Conclusions
Preliminary results from the first season of surveys indicate that sites with large patches with lower amounts of surrounding grassland habitat showed the highest median values of monarch egg and larval per plant density throughout the summer. These results could be useful to property managers looking to expand habitat patches for monarchs. If this pattern holds after another year of data collection in summer 2019, trends would indicate that large milkweed restoration efforts should take place in grassland areas with low surrounding grassland for maximum use of the planted milkweed by monarchs.