Species Profile

Quick Facts

  • The eastern monarch population migrates over 5,000 miles round trip to reach overwintering grounds in Mexico.
  • The western monarch populations migrate to overwintering sites on the Pacific coast, such as Pismo Beach or Natural Bridges in Santa Cruz.
  • The monarch’s migration is not made by a single generation; it takes four generations of monarchs to mate, hatch, metamorphose, and complete a full migration cycle.
  • The milkweed that monarchs eat as caterpillars contains a poisonous toxin that is stored in their bodies; they retain that toxin in their bodies throughout their lives, and it protects them from predators.



Monarch butterfly populations have declined about 90% over the past twenty years. In 2019, the U.S. Fish and Wildlife service is slated to make a determination about whether the monarch butterfly must be listed under the Endangered Species Act.


The monarch butterfly is an iconic species - generations of school children learn about the monarch’s life cycle as it completes its metamorphosis from caterpillar into butterfly and migrates thousands of miles. A crucial component of that life cycle is milkweed, a wildflower. Monarchs lay their eggs on milkweed, and milkweed is the only food that monarch caterpillars eat.


Loss of milkweed breeding habitat, largely due to land use change and widespread application of herbicides, is a critical driver of monarch butterfly population declines. By planting milkweed and other native, nectar-producing plants, landowners can help save the monarch butterfly.