Each fall, North American monarchs travel from their summer breeding grounds to overwintering locations. East of the Rocky Mountains, monarchs travel up to an astonishing 3,000 miles to central Mexico, whereas the shorter western migration is to the California coast. There is evidence of some interchange between the eastern and western populations, perhaps when individuals cross the Rocky Mountains, when butterflies fly from the western U.S. to the Mexican wintering sites, or butterflies from the Mexican sites fly into the western U.S.
Monarchs and Milkweed Citizen Science Monitoring Program
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Milkweed is an essential feature of quality monarch habitat. There are over 100 species of milkweed in North America, though monarch conservation organizations have prioritized species for each region of the U.S. The Monarch Joint Venture has produced a Milkweed Fact Sheet describing these priority species.
Many milkweed species are very hardy and grow in various landscapes. Common places to find milkweed include short and tall grass prairies, livestock pastures, agricultural margins, roadsides, wetland areas, sandy areas, and gardens. Though monarchs do use sites with very few milkweed plants, more plants can support more monarchs. Fewer plants may result in higher per plant monarch density, which can increase the risk of spreading disease and can result in competition for food between larvae.
Including native milkweed species in your monarch habitat is extremely important. Not only does native milkweed offer a food source for monarch larvae, but it provides nectar for a variety of other pollinators and also provides habitat for many other organisms. Native plants are well adapted for the climatic conditions of their region and are easy to care for. Diversity in native plant communities supports many native insects and also provides a number of ecological benefits, such as erosion reduction and filtration.
Unlike larvae that rely only on milkweed to survive, adult monarchs use diverse nectar sources for food. Nectar plants are a key component to prime habitat for monarchs and other pollinators.
Spring blooming nectar plants (blooming approximately March 20—June 1) fuel the monarch migration northward from Mexico and inland from the California coast. Without abundant nectar sources through the migratory corridors, monarchs are less likely to survive and may not be able to reproduce successfully. Summer blooming nectar sources (blooming approximately June 2—August 15) throughout the breeding range are vital to sustain a healthy breeding population. Fall blooming nectar plants (blooming approximately August 16—October 30) are equally important; monarchs rely on abundant nectar sources in the fall to store enough energy not only to survive the long journey to their overwintering sites, but also to survive winter with very minimal nectar availability.
While non-native species can be used for nectar, native nectar plants are significantly more beneficial to an ecosystem. Native plants are well suited for the climatic conditions of an area and are responsible for important ecosystem functions, such as erosion control and filtration.
The area surrounding a monarch habitat can influence monarch use of a site and survival. Land use changes have caused natural areas to be fragmented into smaller, more distant parcels of land disbursed throughout an ecosystem. Surrounding areas covered by natural vegetation are more beneficial to monarchs than surrounding land that has been altered by development or agriculture.
Natural vegetation surrounding any wildlife habitat reduces the risk of danger by human contact. Milkweed habitat mixed within human inhabited areas is important for monarch populations, but it can increase the risk of injury or death to monarchs by vehicles or human activity, such as pesticide use. Monarch breeding habitats in close proximity to each other allow monarchs to find suitable habitat without traveling long distances.
Environmentally friendly management practices are important for successful monarch conservation. These land management activities can help to reduce the effects of habitat disruption and can promote native growth in a habitat. Replacing non-native species with native species encourages a healthy diversity of plants and animals in an ecosystem and provides more ecological benefits. Some management strategies important to monarch habitat conservation include prescribed burning, timely mowing, native seed collection, native planting, and exotic species control.