Western Monarchs

February 24, 2022

Question: New data shows that overwintering numbers for western monarch butterflies improved to almost 250,000 in the past year. Has the western monarch population recovered?

Answer: Although CDFW is cautiously optimistic about the new data, it does not represent a full recovery. The 2021-22 overwintering numbers improved significantly but they still represent a one-year trend. Prior to the 1980s, California hosted between one to four million overwintering butterflies each year. When viewed through that lens, 200,000 western monarchs is less than 20 percent of the historical average. When viewed through that lens, 200,000 western monarchs is less than 85 percent of historic numbers. We saw western monarchs decline from around 200,000 to less than 2,000 in just three years (2016-2018), indicating they are still vulnerable at that population size. Finally, monarchs were concentrated in overwintering sites along the Central Coast between Los Angeles and Monterey counties, while the Bay Area supported fewer than 600 monarchs this year despite having robust populations in the past. We’d like to see monarch numbers increase across their entire historic range and better understand why they were not uniformly distributed this year.

Despite these concerns, CDFW remains encouraged by the data and inspired to build on the past year’s success. We’re focused on improving management of CDFW-owned overwintering sites and increasing the availability of early-season milkweed to support first generation monarchs. We encourage the public to use habitat-based approaches to conservation (such as planting regionally appropriate native milkweed and nectar plant species) and to participate in community science projects that help track the status of the western monarch population.

Always appreciate your reports on animal population trends and management actions Hojoman. Keep them coming.