Each fall season, thousands of monarch butterflies from western Canada start their long migration towards the southwest. A migrating population of monarchs arrives in November in Pacific Grove and stays through February before returning back north. But Pacific Grove is not the only site in California. There are more than 300 overwintering sites in the state.
Butterflies can be seen fluttering about on sunny days throughout the Asilomar grounds and dunes. But as the day grow colder, they will fly inland to the Monarch Grove Sanctuary and cluster in Monterey pines and eucalyptus trees. The sanctuary is located in Pacific Grove just off Lighthouse Avenue on Ridge Road. The microclimate in the closed canopy of trees provides a buffer from the winds, and the temperatures can remain moderate.
In February, the monarch butterflies will mate. The males will die and the females will begin the migration north. Along the migration route the female will find milkweed plants and lay her eggs on the underside of the leaves, imprinting her offspring with the genetically coded message of the migration route. Once the eggs are laid, the female will die. The eggs will develop and, after emerging from a chrysalis, the new generation of butterflies will continue the migration north. Two more generations of monarch butterflies will develop before reaching western Canada. The fourth and longest-lived generation will fly the entire southward migration back to Pacific Grove.