Environment & Science

Help count butterflies to gather information on their population growth

The Xerces Society
Volunteers counting monarchs clustering in a grove.
Carly Voight/The Xerces Society
The Xerces Society.


Monarch butterflies have been petitioned to be protected as a threatened species under the Endangered Species Act. One nonprofit concerned about the future of these butterflies is seeking "citizen scientists" to help them gather information on the habitat conditions and population numbers of monarchs spending their winters on the California coast.

The Xerces Society — a nonprofit that protects wildlife through the conservation of invertebrates and their habitats — says monarch populations have greatly dropped over time.

"[Monarchs] have gone from historically numbers of about a billion, to last year there were about 50 million of them," Sarina Jepsen, endangered species program director at Xerces Society, told KPCC.

The western monarch population that winters along the California coast has declined 5o percent since 1997, she said. 

In order to find out the current population status of western monarchs, the Xerces Society organizes the Western Monarch Thanksgiving Count annually to help keep estimated population information on the species.

Monarch populations expand into other western states during the spring and summer, Jepsen said. Western monarchs are mainly seen in California during the fall and winter, making the time around Thanksgiving a great opportunity to gather data.

"When monarchs are congregated so tightly together like they are in California [at sites where they spend the winter] it provides a great opportunity for people to count them, as opposed to trying to count them when they're dispersed through the entire western landscape," Jepsen said.

Every year since 1997, the organization has gathered volunteers who visit these sites on the California coast and count monarchs that cluster on trees. Volunteers leave with data that helps the organization develop information on the monarch population.

"Thanks to the efforts of all these volunteers, we have an understanding of how monarchs in the western U.S. and specifically monarchs [in California] are doing," Jepsen said. 

How you can help

You can sign up to help at WesternMonarchCount.org. At the site, you can get more information on places that need monitoring. 

Volunteers are trained in how to count the butterflies and submit data. No professional experience is needed.

"You don't need to have an advanced degree or anything like that to count monarch butterflies, but we do like to make sure that everyone who is participating in this project is counting monarchs in the same way," Jepsen said.