Monarch butterflies, with their orange and black wings, are an iconic species known for their remarkable cross-continental migration. While not extinct, their populations have significantly declined in recent decades, indicating a complex status.
The Monarch’s Remarkable Journey
Monarch butterflies undertake a multi-generational migration across North America. Their life cycle begins as an egg laid exclusively on milkweed plants, hatching into a caterpillar that feeds on the leaves. This caterpillar then transforms into a chrysalis before emerging as an adult butterfly. The North American monarch population is divided into two main migratory groups: the Eastern and Western populations.
The Eastern population travels from southern Canada and the U.S. to overwinter in the oyamel fir forests in central Mexico. Western monarchs, west of the Rocky Mountains, migrate to coastal California. This complex life cycle, involving multiple generations to complete the round trip, and the extensive distances covered contribute to their vulnerability, as they depend on specific habitats along their entire migratory pathway.
Current Population Status
The Eastern population is monitored by measuring the acreage of forest occupied by overwintering colonies in Mexico. The latest surveys for the 2024-2025 winter season showed the Eastern population occupied 1.79 hectares, representing a 99% increase from the previous year’s 0.9 hectares. However, this figure remains below the average of 2.81 hectares for the past decade and is considerably lower than the 45 acres observed in 1996-1997.
The Western monarch population, overwintering in coastal California, is monitored through direct counts. In January 2025, just over 9,000 monarchs were counted in California, the second lowest number ever recorded, contrasting sharply with millions observed in the 1980s. The International Union for Conservation of Nature (IUCN) initially listed the migratory monarch butterfly as Endangered in July 2022, but later changed its status to Vulnerable in December 2023. The U.S. Fish and Wildlife Service proposed listing the monarch as threatened under the U.S. Endangered Species Act in December 2024.
Key Factors Impacting Monarchs
Several interconnected threats impact monarch populations across their migratory range. Habitat loss is a primary concern, affecting both their breeding grounds and overwintering sites. This includes the reduction of milkweed, which is the only plant monarch caterpillars can eat, and the diminishing availability of nectar-producing plants that adult butterflies rely on for energy.
Pesticide use also contributes to their decline. Herbicides destroy milkweed in agricultural fields and roadsides, while insecticides harm butterflies and their larvae. Climate change exacerbates these issues by impacting weather patterns, altering migration timing, and affecting overwintering suitability. These factors collectively reduce monarch resources and disrupt the balance necessary for their survival.
Protecting Monarchs
Efforts are underway to conserve monarch butterflies and reverse population declines. Large-scale initiatives include restoring habitat across migratory routes and protecting overwintering sites, like the Monarch Butterfly Biosphere Reserve in Mexico. These projects focus on creating and maintaining landscapes that provide both milkweed for caterpillars and diverse nectar sources for adult butterflies.
Individuals can contribute to monarch conservation. Planting native milkweed is impactful, as it serves as the sole host plant for monarch eggs and caterpillars. Supplementing milkweed with native, nectar-rich flowering plants provides food for adult monarchs throughout breeding and migration. Reducing pesticide use in gardens and communities protects monarchs from harmful chemicals. Supporting conservation organizations dedicated to monarch research and habitat restoration strengthens these efforts.