Monarch butterflies in their overwintering grounds in Mexico.

Where Do the Monarchs Go in the Fall?

Every fall, millions of monarch butterflies embark on a journey that will take them up to 3,000 miles south to the remote mountain treetops of Central Mexico and Southern California. This great migration is one of the most spectacular natural phenomena in the world. Unfortunately, there is reason to be concerned about the future of the monarch migration and the perpetuation of the species.

The monarchs cannot survive the cold winters of the northern climates, so they must use environmental cues and move to warmer climates. The eastern population of North America's monarchs overwinter in oyamel fir forests in Mexico, which provide ideal microclimates for the butterflies. Monarchs living west of the Rocky Mountain range overwinter in California along the Pacific Coast near San Diego. Here, they roost in eucalyptus, Monterey pines, and Monterey cypresses. Conservation of the monarchs overwintering habitats is critical to their survival.

Because the monarchs are concentrated in just a few locations during the winter months, they are vulnerable to harsh weather conditions and human activities that can destroy their habitats. In 2016, a wicked storm tore through the overwintering colonies in Mexico, resulting in a population loss of about 6.2 million monarchs. Luckily, an unseasonably warm fall produced an extra generation of migrating monarchs which helped boost the 2017 overwintering population. This indicates that monarchs are resilient creatures and efforts to protect them are working.

The monarchs that migrate to Mexico in the fall are the same ones returning to lay their eggs in the spring, who will be seeking fresh milkweed in the southeastern United States. By planting native milkweed in your landscape and encouraging roadside managers, park maintenance, golf courses and companies with large land holdings to do the same, you can provide food for the monarch caterpillar and enjoy the beauty of the monarchs when they visit. Your ability to make a difference is larger than you might think!