Every year in late summer and early fall, western monarchs journey back to more than 200 overwintering sites up and down the California coast. Here, they gather by the dozens, hundreds, and even thousands to rest for the winter, before mating in the spring and starting the cycle all over again. Citizen scientists monitor these overwintering groves each year, gathering information on habitat conditions and estimating population numbers. The highlight of this effort is the annual Western Monarch Thanksgiving Count (WMTC), which takes place for three weeks around the Thanksgiving holiday. To learn more about the count and find out how you can get involved, read more here. If you're visiting an overwintering site, don't forget to keep an eye out for tags this season too!
A new Xerces report, State of the Monarch Butterfly Overwintering Sites in California, documents a 74% decline in the number of overwintering monarchs in CA in less than two decades. The data used was largely generated by volunteers of the Western Monarch Count, who's dedication makes this important monitoring of monarch populations possible. Thank you to all our volunteers and volunteer coordinators for continuing to advocate for and support Western monarch conservation efforts!
There's a new way to record monarch data! The Monarch SOS App v. 2.1 is available free from iTunes for use on iPhone (an Android version is in the works). Check out the many citizen science projects related to monarchs including the Xerces Western Monarch Count for overwintering sites in California and the Xerces/USFWS Western Milkweed and Monarch Breeding survey for collecting information throughout the West during the breeding season. ... See MoreSee Less
Did you know that the data you collect at overwintering sites are used for more than just tracking the annual population of monarchs on the CA coast? Check out our recently updated list of publications and resources that put these data to use! ... See MoreSee Less
Frey, D. and A. Schaffner. 2004. Spatial and temporal patterns of monarch overwintering abundance in Western North America. In Oberhauser, K.S. and M.J. Solensky, eds. The Monarch Butterfly: Biology a...
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Monarch overwintering site location data provided by this website is for basic navigational purposes only and is not intended to be relied upon in situations where precise location information is needed or where erroneous, inaccurate or incomplete location data may lead to personal injury, death, or property or environmental damage. Neither we, nor any of our content providers, guarantee the availability, accuracy, reliability, or timeliness of location data displayed by our website.
Participants of this citizen science project assume all responsibility for following the rules and regulations of the areas in which they are surveying, including all notices of private property and no trespassing warnings. The Xerces Society encourages all participants to follow basic common sense and safety precautions when accessing and monitoring overwintering sites. Participants are ultimately responsible for their own safety and well-being.