By California State Parks Foundation, November 2021
Once, millions of monarchs overwintered along the Pacific coast in California and Baja, Mexico. In the 1980s, an estimated 4.5 million butterflies migrated to the coast annually. But by the mid-2010s, the population declined to 200-300 thousand butterflies. And in both 2018 and 2019, volunteers counted under 30,000 monarchs — less than 1% of the population’s historic size.
In 2020, volunteers counted less than 2,000 monarchs — that’s less than 0.01% of the historic size.
Western Monarchs living west of the Rockies migrate to the coast of central and southern California. In October, as colder weather approaches, the butterflies instinctively know they must fly south to escape the freezing temperatures. Some have to fly over 1,000 miles. By November, most are sheltering in trees across California – and many are in California state parks!
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