Partnering to Conserve the Monarch Butterfly Migration

Colony estimates at central Mexico overwintering sites indicate that monarch butterfly (Danaus plexippus) populations have declined over the past two decades. Among the leading causes of this long-term trend are:

Deforestation and forest degradation in the butterfly's overwintering sites
Climate change punctuated by episodic extreme weather conditions in the butterfly's migratory range (central Mexico, United States, and southern Canada)
Loss of milkweed (Asclepiadaceae) host plants in the spring and summer breeding habitat in the United States

A combination of roadside and site-specific surveys, greenhouse experiments, and field experiments will be used to:

Determine the density of native milkweed populations in seven of the ten Texas ecoregions
Determine the species of milkweed preferred by monarch butterflies
Determine seed viability and growth requirements for preferred milkweed species
Evaluate the temporal effects of mowing and the spatial/density influence of Solenopsis invicta (fire ants) on milkweed and monarch butterfly eggs and larvae

This research will result in a comprehensive report on the current status of native milkweeds for a large swath of Texas and will also determine which milkweed host plants are preferred by monarchs. Combined with findings about the milkweed species' optimal growth requirements, this study will guide statewide management strategies and conservation efforts and ultimately help refine recommendations by the U.S. Fish and Wildlife Service.