Every autumn, the western North American population of monarch butterflies migrates from the lands west of the Rocky Mountains to the coast of California, where they spend the winter at about 200 sites scattered throughout the coastline. Last winter, I had a chance to visit the Monarch Grove in Santa Cruz, California, where thousands of monarchs were resting in eucalyptus trees and occasionally fluttering about in search of water or nectar. As a monarch conservation biologist who entered the field only after the monarch population plummeted in size, seeing the monarch overwintering in California was an amazing sight. In just one glance, I was able to see more monarchs in Santa Cruz’s Monarch Grove than I normally see in an entire summer. Unfortunately, even the thousands of monarchs I saw were just a fraction of the numbers once found at that overwintering site.
Despite the declining monarch population, many of the overwintering sites up and down the California coast are popular spots for tourists who, like me, want to see monarchs en masse. But, tourists aren’t the only people visiting the groves; citizen scientists with the Western Monarch Thanksgiving Count (WMTC) go to these sites in order to count the number of monarchs present. Candace Fallon, a conservation biologist who coordinates the WMTC, says that citizen scientists with WMTC provide a “comprehensive, long term data set for the overwintering population.” The data they collect allow scientists to estimate the number of the western monarchs, and were recently used in a scientific paper detailing the population decline of western monarchs.
Eva Lewandowski, Discover Magazine
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