Land use and management practices: Implications for the monarch butterfly in the southern Great Plains
Monarch butterflies (Danaus plexippus) are known for their long-distance migration from summer breeding sites in the upper Midwest and Canada to overwintering grounds in Mexico. Monarchs pass through the southern Great Plains during both their spring and fall migrations, and this region is important for both early and late season reproduction and providing floral resources during migration. Land use and management practices can influence milkweed availability (both quantity and quality), floral resource availability, and habitat suitability for monarchs. We evaluated the effects of land use and management practices on resources for monarch butterflies in Oklahoma, including monarch density and reproductive success. We focus on Asclepias viridis, which is the most common host plant throughout much of this region. We also evaluate parasitism by Ophryocystis elektroscirrha (a spore-forming protist that specializes on monarchs and queens) and Lespesia archippivora (a tachinid fly which is considered a generalist on lepidopteran larvae).
The density of milkweed varies among land use types, but is consistently more abundant when monarchs are present in this region during the spring than during the fall. Management practices influence the availability of milkweed, especially in the fall when the above ground portion of A. viridis has senesced in many areas without disturbance. The density of larval monarch butterflies is higher in the fall than in the spring, and varies with land use type and management practices. Parasitism rates vary among years and with land use type and management practices, and can be locally very high at some sites. Results from this study are discussed in the broader context of milkweed availability throughout the monarch’s breeding range, as well as seasonal and geographical patterns in parasitism.