Monarch butterflies migrate primarily to two main overwintering sites depending on their population location:
- Eastern North American monarchs migrate thousands of kilometers south to the mountainous oyamel fir forests in central Mexico, mainly the Trans-Mexican Volcanic Belt area in the states of Michoacán and México. They arrive there around November and overwinter on the trees until starting their northward migration in spring.
- Western North American monarchs, those living west of the Rocky Mountains, migrate shorter distances to the coast of California, where they overwinter in groves of eucalyptus or Monterey pine trees near places like Pacific Grove.
There are also smaller or non-migratory monarch populations in places like Florida, the Caribbean, and Australia, but the most famous mass migration is the long southward journey to central Mexico by eastern population monarchs. This migration is considered one of the most remarkable natural phenomena.
