Monarch Monitoring – Help Count These Magnificent Migrators to Aid Conservation Efforts

Monarch butterflies clustering on a tree at an overwintering site in Pacific Grove, CA.

The monarch butterfly is a remarkable species.  Each year these insects migrate in a similar pattern to birds from colder to warmer climates as the seasons change, often returning to the same overwintering sites every year.  Unlike birds, however, no single monarch lives long enough to make the whole migration, so the journey occurs across multiple generations, adding to the complexity and incredible nature of the phenomenon. There are two main groups of monarchs in North America that are distinguished by their migration routes: the eastern group spends its spring and summer in eastern or central U.S and overwinters in Mexico, while the western group lives in central California and surrounding states for most of the year, overwintering on the California coast.  Although these two groups are the same species, they are studied independently, as different factors affect their life cycles and migrations.

The Xerces Society, an organization dedicated to the conservation of invertebrates including insects, has been studying the western monarch population for nearly two decades through a citizen science project called the Western Monarch Thanksgiving Count.  The project asks volunteers to travel to monarch overwintering sites on the California coast and count the butterflies that are present.  Sarina Jepsen from the Xerces society describes that the project is “really an extraordinary effort” because of the sheer number of monarchs and their broad distribution across the California coastline.  She notes that the project provides “the primary information” the society has to understand annual changes in the monarch population.

A monarch butterfly on its primary food supply, milkweed.

So far, the count has provided scientists with two important pieces of information.  The first is that the monarch population has declined dramatically over the last 15 years – on average, only 10% of monarchs are returning to their overwintering sites compared to 1997.  A recent study has linked this decline in part to climate change, which affects the monarch’s primary food source and mating ground, the milkweed plant. The second piece of information from the count, as Jepsen describes, is a “spatial picture of how the monarchs are doing and areas that can be prioritized for conservation projects.” Another factor in the monarch decline is the loss or degradation of over wintering sites, so a detailed picture of their distribution in the winter is critical to maintaining the remaining sites that these butterflies use.

Although many of the people participating in the project have been dedicated for a number of years, the Xerces Society is always looking for new volunteers to join in the count.  Jepsen asserts that for new participants helping out, “It’s our hope that they’ll develop an appreciation of monarch butterflies and a desire to work towards their conservation.” The count takes place for three weeks around the Thanksgiving holiday, so it’s a great activity to burn off some of those extra holiday calories while aiding in the conservation of these incredible insects.

Reference: Xerces Society

Images: Top – wikipedia via california photo scout; Bottom – Xerces Society


Emily Lewis is a PhD candidate in chemistry at Tufts University, where she analyzes catalysts for synthetic fuels on the nanoscale. She received her BS and MS degrees from Northeastern University, and her thesis work examined fuel cell catalysts under real operating conditions. She loves learning about energy and the environment, exploring science communication, and investigating the intersection of these topics with the policy world. When she’s not writing or in the lab, you’ll probably spot Emily at the summit of one of the White Mountains in NH. Follow her: @lewisbase,

Categories: Animals, Citizen Science, Ecology & Environment, Insects, Nature & Outdoors