Urges Increased Public Engagement to Help Save the Species
- Read the press release
- Proposed rule to list the monarch butterfly as a threatened species
- Monarch Species Status Assessment Version 2.3
- Learn how you can help save the monarch
- Learn more about the monarch initiative, including how to submit comments and register for public meetings
Questions and Answers
Overview
Monarch butterflies are pollinators that are well known for their impressive long-distance migration and their recent declines. The species highlights the need for conservation efforts for all pollinators across the nation. Learn more about monarch conservation efforts, including what the U.S. Fish and Wildlife Service is doing and how you can help.
With its iconic orange and black markings, the monarch butterfly is one of the most recognizable butterfly species in North America. Their bright coloration serves as a warning to predators that eating them can be toxic, and monarchs obtain these toxins (called cardenolides) by consuming milkweed plants.
Originally native to North America, the monarch butterfly has dispersed to other parts of the world and non-migratory populations are found from islands in the Pacific Ocean to the western edge of Europe. Despite this expansion, most monarchs continue to live and migrate in North America. North American migratory monarchs are divided into eastern and western populations. The Rocky Mountains generally divide these two populations, limiting their contact. However, the two populations are not completely isolated from each other and still occasionally interbreed. There are also non-migratory monarchs that remain year-round at the southern end of their breeding range in North America, including in parts of Florida, the Gulf Coast and California.
The eastern North American migratory monarch population is the largest population of monarchs, in both individuals and range. The eastern population encompasses upwards of 70% of the total North American monarch range. In the fall, they may fly more than 2,000 miles (3,000 km) to reach overwintering sites in Mexico.
The western North American migratory monarch population is generally found west of the Rocky Mountains. These butterflies can migrate annually 300 to 1,000 miles (about 500 to 1,600 km). The western population overwinters in hundreds of groves (clusters of trees) along the California coast and into northern Baja California, Mexico.
Scientific Name
Identification Numbers
Characteristics
Food
Monarch butterflies require healthy and abundant milkweed plants for both laying eggs on and as a food source for caterpillars. By consuming milkweed plants, monarchs obtain toxins, called cardenolides, that provide a defense against predators. Additionally, a wide variety of blooming nectar resources (flowers) are needed for adults throughout the breeding season, migration and overwintering.
In western North America, nectar and milkweed resources are often associated with riparian riparian
Definition of riparian habitat or riparian areas.
Learn more about riparian corridors, and milkweed may function as the principal nectar source for monarchs in more arid regions.
Dilts TE, Steele M, Black S, Craver D, Cruz E, Engler J, Jepsen S, Jones A, McKnight S, Pelton E, Taylor A, and Forister M. 2018. Western Monarch and Milkweed Habitat Suitability Modeling Project Version 2 – Maxent Model Outputs. Xerces Society/US Fish and Wildlife Service/University of Nevada Reno. Dingle H, Zalucki MP, Rochester WA, Armijo-Prewitt T. 2005. Distribution of the monarch butterfly, Danaus plexippus (L.) (Lepidoptera: Nymphalidae), in western North America. Biological Journal of the Linnean Society 85:491-500.
Pelton E, McKnight S, Fallon C, Code A, Hopwood J, Hoyle S, Jepsen S, Black SH. 2018. Managing for monarchs in the West: Best management practices for conserving the monarch butterfly and its habitat. Portland, OR: The Xerces Society for Invertebrate Conservation. vi + 106 pp.
Waterbury B, Potter A. 2018. Integrating strategic conservation approaches for the monarch butterfly in the State Wildlife Action Plans of Idaho and Washington. Final report prepared for the U.S. Fish & Wildlife Service. 79 pp.
Habitat
Whether it’s a field, roadside area, open area, wet area or urban garden, milkweed and flowering plants are needed for monarch habitat. Adult monarchs feed on the nectar of many flowers during breeding and migration, but they lay eggs on milkweed plants as that is the only food the caterpillars can eat.
For overwintering monarchs, habitat with a specific microclimate is needed for protection from the elements, as well as moderate temperatures to avoid freezing. These conditions vary between populations.
For the eastern North American population, most monarchs overwinter in oyamel fir tree roosts located in mountainous regions of central Mexico, at an elevation of about 8,000 to nearly 12,000 feet (2,400 to 3,600 meters) - over two miles up!
Monarchs living west of the Rocky Mountains in North America primarily overwinter in California at sites along the Pacific Coast, roosting in eucalyptus, Monterey pines and Monterey cypress trees.
Food
Monarch butterflies require healthy and abundant milkweed plants for both laying eggs on and as a food source for caterpillars. By consuming milkweed plants, monarchs obtain toxins, called cardenolides, that provide a defense against predators. Additionally, a wide variety of blooming nectar resources (flowers) are needed for adults throughout the breeding season, migration and overwintering.
In western North America, nectar and milkweed resources are often associated with riparian riparian
Definition of riparian habitat or riparian areas.
Learn more about riparian corridors, and milkweed may function as the principal nectar source for monarchs in more arid regions.
Dilts TE, Steele M, Black S, Craver D, Cruz E, Engler J, Jepsen S, Jones A, McKnight S, Pelton E, Taylor A, and Forister M. 2018. Western Monarch and Milkweed Habitat Suitability Modeling Project Version 2 – Maxent Model Outputs. Xerces Society/US Fish and Wildlife Service/University of Nevada Reno. Dingle H, Zalucki MP, Rochester WA, Armijo-Prewitt T. 2005. Distribution of the monarch butterfly, Danaus plexippus (L.) (Lepidoptera: Nymphalidae), in western North America. Biological Journal of the Linnean Society 85:491-500.
Pelton E, McKnight S, Fallon C, Code A, Hopwood J, Hoyle S, Jepsen S, Black SH. 2018. Managing for monarchs in the West: Best management practices for conserving the monarch butterfly and its habitat. Portland, OR: The Xerces Society for Invertebrate Conservation. vi + 106 pp.
Waterbury B, Potter A. 2018. Integrating strategic conservation approaches for the monarch butterfly in the State Wildlife Action Plans of Idaho and Washington. Final report prepared for the U.S. Fish & Wildlife Service. 79 pp.
Behavior
The monarch butterfly’s annual fall migration is one of nature’s greatest phenomena. The monarch's journey is one of the longest known insect migrations in the world. Each fall, the eastern and western North American monarchs go into a state of suspended reproduction, known as diapause, and begin migrating to their respective overwintering sites. The eastern population of monarchs travel up to 3,000 miles during migration traveling from Canada, through the U.S. and down to Mexico - a trip that may last more than two months. Tagging and observational data suggest that monarchs can travel up to approximately 70 to 75 miles a day during migration. The longest single day flight of a tagged eastern North American monarch was recorded at 265 miles.
In early spring, surviving monarchs break diapause and mate at the overwintering sites before dispersing. The same individuals that undertook the initial southward migration begin flying back through the breeding grounds. After several generations of monarch offspring in the spring and summer, a new generation begins the fall migration for the first time.
With the year-round presence of milkweed and suitable temperatures, monarchs in many areas of the their worldwide range, including parts of North America, live and breed year round. Many of these non-migratory monarchs are genetically distinct from the migratory North American monarchs, although the southern Florida population gets an annual influx of individuals from the eastern monarch population.
Knight A, Brower LP. 2009. The influence of eastern North American autumnal migrant monarch butterflies (Danaus plexippus L.) on continuously breeding resident monarch populations in southern Florida. Journal of Chemical Ecology 35:816-823.
Pfeiler E, Nazario-Yepiz NO, Pérez-Gálvez F, Chávez-Mora CA, Laclette MRL, Rendón-Salinas E, Markow TA. 2016. Population genetics of overwintering monarch butterflies, Danaus plexippus (Linnaeus), from central Mexico inferred from mitochondrial DNA and microsatellite markers. Journal of Heredity 108:163-175.
Zhan S, Zhang W, Niitepold K, Hsu J, Haeger JF, Zalucki MP, Altizer S, de Roode JC, Reppert SM, Kronforst MR. 2014. The genetics of monarch butterfly migration and warning colouration. Nature 514:317-321.
Physical Characteristics
The large and brightly colored monarch butterfly has two sets of wings that span three to four inches. Monarch caterpillars, or larvae, have black, yellow and white stripes and reach lengths of two inches before metamorphosis. Monarch caterpillars then pupate into a green and gold chrysalis and emerge six to 14 days later as adult butterflies.
Compared to monarchs from most non-migratory populations, monarchs from the eastern North American migratory population have unique physical characteristics, tending to have larger bodies and larger, elongated wings. In addition, the eastern North American migratory monarchs tend to have redder coloration, a trait associated with their ability to fly for longer periods of time. The mechanism for this correlation is unknown.
Measurements:
Wingspan: 3 to 4 inches (7 to 10 cm)
Larval length: 2 inches (5 cm)
Altizer S, Davis AK. 2010. Populations of monarch butterflies with different migratory behaviors show divergence in wing morphology. Evolution 64:1018-1028.
Davis AK. 2009. Wing color of monarch butterflies (Danaus plexippus) in eastern North America across life stages: Migrants are redder than breeding and overwintering stages. Psyche 2009:1-5.
Davis AK, Chi J, Bradley C, Altizer S. 2012. The redder the better: Wing color predicts flight performance in monarch butterflies. PLOS ONE 7:e41323.
On average, adult monarch butterflies weigh about half of a gram, which is less than the weight of a paperclip.
Adult monarch butterflies are large and conspicuous, with bright orange wings surrounded by a black border and covered with black veins. The black border has a double row of white spots, present on the upper side of the wings. Adult monarchs are sexually dimorphic, with males having narrower wing venation and scent patches. The bright coloring of a monarch serves as a warning to predators that eating them can be toxic.
Bouseman JK, Sternburg JG. 2001. Field guide to butterflies of Illinois. Illinois Natural History Survey. Champaign, IL.
[CEC] Secretariat of the Commission for Environmental Cooperation. 2008. North American monarch conservation plan. Communications Department of the Center for Environmental Cooperation Secretariat.
Life Cycle
Monarchs begin their lifecycle as eggs, which are laid on milkweed plants and hatch after two to five days. The eggs hatch into caterpillars and progress through five instars over the next two weeks before pupating into a green and gold chrysalis. An adult monarch will emerge one to two weeks later.
Herman WS, Tatar M. 2001. Juvenile hormone regulation of longevity in the migratory monarch butterfly. Proceedings of the Royal Society B-Biological Sciences 268:2509-2514.
Most breeding adult butterflies live approximately two to five weeks, but overwintering adults that enter into reproductive diapause can live six to nine months.
As temperatures warm at the overwintering sites in the spring, monarchs begin to breed and lay eggs on milkweed throughout their spring journey. The following generations breed and lay eggs throughout the spring and summer. In the fall, monarchs enter a state where they stop reproducing, known as diapause. This allows them to focus their energy and resources on the long-distance migration and surviving the winter. Some non-migratory monarchs in warmer climates breed year-round.
Similar Species
Adult butterfly species that look similar to the adult monarch are soldier butterfly (Danaus eresimus), queen butterfly (Danaus gilippus) and the viceroy (Limenitis archippus).
Geography
Monarchs are native to North and South America but have since spread to many other locations where milkweed and suitable temperatures exist, including Australia, New Zealand and portions of the Iberian Peninsula.
Timeline
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