Pismo Beach

Each fall thousands of Monarch Butterflies migrate to Pismo Beach. From late October to February, the butterflies cluster in the limbs of Eucalyptus trees at Pismo State Beach and docents provide twice daily talks to visitors of the grove.

Historic winter counts at this sight and others reveal a disturbing trend; there are far fewer Monarch Butterflies.  Although still remarkably numerous, monarch butterflies have dwindled in numbers (a decline of over 90%) over the past quarter century. There is a broad international effort to understand why and how to reverse the trend.

A group of researchers from the U.S. Fish and Wildlife Service, Winston-Salem State University in North Carolina and the U.S. Geological Survey are testing a new method for estimating monarch populations that could bring increased precision to the current process. The new technique uses LASERS. Drs. Nick Hristov and Louise Allen of Winston-Salem State University pioneered the use of Light Detection and Ranging (also known as LiDAR) to estimate wildlife populations. Overwintering sites are scanned with the LiDAR device once while monarchs are present, and once after dispersal from overwintering sites. By mapping the surface area with and without monarchs, combined with an estimate of density, it is possible to estimate the number of butterflies at these overwintering colonies.

Docents at Pismo Beach will soon be able to talk to park visitors about these research developments.  To read more about the team’s work, check out www.fws.gov/cno/newsroom/highlights/2018/monarch_lidar_count/