A wonder of nature, the migration of the monarch butterfly (Danaus plexippus) across eastern North America is a journey that especially involves Arkansas, as a state that lies within the heart of the monarch’s migratory path and provides habitat for the first and last generations every year. The ANHC plays a significant role by providing landscape-scale habitat for this iconic species (and many, many others) through the 72,117-acres included in the System of Natural Areas. State-owned natural areas protect thousands of acres of prairie, savanna, woodland, and glade habitat that are critical for the monarch. These sites support milkweeds (Asclepias spp.), which serve as food for monarch caterpillars, and a wide diversity of flowering plants rich in nectar for adults.

In North America, there are two distinct migratory populations of monarchs separated by the Rocky Mountains: a western population that overwinters in California, and an eastern population that overwinters in high-elevation oyamel fir (Abies religiosa) forests in central Mexico. Every spring, the eastern migration starts when monarchs leave their wintering grounds in Mexico and fly north. On wings weathered by the elements, individuals land in northern Mexico and the southern U.S. beginning in late March, finding rest in rights-of-way, prairies, woodlands, gardens, agricultural fields, and more. Female monarchs will have mated in the overwintering colonies, so when they arrive in Arkansas, they lay eggs on their milkweed host plant and die shortly thereafter. The resulting offspring that hatch and develop into adults constitute the first generation of monarchs, which migrate further north, mating and laying their eggs along the way. Ultimately, four generations of monarchs fan out across the eastern United States and southern Canada throughout spring and summer.

Many adult monarchs that emerge in late summer (some of the third generation, and most of the fourth generation) enter reproductive diapause in response to decreasing temperatures and day length, which causes their reproductive organs to remain in an immature state. Diapause enables these individuals to conserve energy for a very special journey: their migration south to Mexico to gather in the forests of their ancestors. Hailed as the “super generation,” these migrating monarchs can live up to nine months, whereas most adult monarchs of earlier generations live only two to six weeks. The spectacular fall migration of monarchs is happening now, with numbers peaking in Arkansas during late September and early October. As they move through the state, monarchs are feasting on nectar-rich forbs (i.e., wildflowers) by day and clustering in roosts by night.

Some monarchs breed and lay eggs in the southern U.S. starting in August, producing what is often considered a fifth generation of monarchs, although it is possible these individuals are part of the fourth generation. In Arkansas, these late offspring have been documented in the form of monarch eggs, caterpillars, and chrysalises from August through early November. There is much to be discovered about these late bloomers, as Dr. Kristen Baum, professor of integrative biology at Oklahoma State University, acknowledges: “Not much is known about the fifth generation, including whether or not it is an important part of the overall eastern North American monarch population.”

Given the need for more information about the “fifth generation” of monarchs produced in Arkansas, it is important to properly document late occurrences of monarchs in every life stage. One of the best ways to record such observations is through the Arkansas Monarch Mapping Project set up in iNaturalist, a website and phone application that helps users identify animals and plants and, in turn, allows scientists to access such data to better understand and protect nature. To enter observations for this iNaturalist project, create a free account and search for “Arkansas Monarch Mapping Project.” Once the project page is up, navigate to the “Add Observations” banner and provide information for your sighting(s). The purpose of the Arkansas Monarch Mapping Project is “to gain a better understanding of the distribution of monarchs in Arkansas and the timing of both spring and fall migrations,” so recording observations of monarchs anytime you see them is encouraged!

The monarch is truly a treasured part of Arkansas’s natural heritage, connecting Arkansans to our natural areas and other places and people across the continent. When monarchs are migrating in fall, they fly in large numbers across cityscapes and countrysides, as well as international borders, and this spectacle has scientific and cultural significance that is worthy of protection. If you’d like to learn more about efforts underway in Arkansas to help preserve the monarch migration for future generations, watch the video titled, “Wings of Hope.”

References

Photos:
Photo 1 — Monarch butterfly (Danaus plexippus) on compass plant (Silphium laciniatum). Photo by Leslie Cooper.

Photo 2 — Monarch butterfly (Danaus plexippus) caterpillar on green milkweed (Asclepias viridis). Photo by Leslie Cooper.

Photo 3 — Monarch butterfly (Danaus plexippus) at Railroad Prairie Natural Area. Photo by Leslie Cooper.