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Rain, Shine or Squirrels, Pacific Grove Counts Western Monarchs

Jan 10, 2017


  • Community Science
  • Migration

Post written by Candy Sarikonda, Monarch Watch Conservation Specialist and Wild Ones Member.

This New Year’s Eve, I joined staff and volunteers from the Pacific Grove Museum of Natural History to conduct a count of the monarch butterflies overwintering at Pacific Grove Monarch Sanctuary (PGMS). The sanctuary has long been a preferred overwintering site in California, one of about 200 sites located along the California coast.  Each year, during a 3-week period around Thanksgiving Day and again around New Year's Day, researchers and volunteers visit overwintering sites to conduct a count of the monarchs spending the winter at these locations.  The Western Thanksgiving Count is coordinated by Mia Monroe and the Xerces Society for Invertebrate Conservation.

This winter, the monarch butterflies at PGMS have been spending much of their time clustered in trees on the neighbors' properties.  But Pacific Grove, known lovingly as Butterfly Town, USA, is a town that loves its monarch butterflies, and we were graciously invited by a neighbor to observe and count the monarchs from her yard.  Nick Stong, Education Programs Manager for the museum, was leading the count, along with seasoned volunteers Stephanie Turcotte and Connie Masotti.  Just as we reached the neighbor's yard, a soft drizzle began. Undeterred, the team counted the number of butterflies in each cluster, located high in a nearby mature Monterey pine tree.  The morning sun shone brightly on the clusters, illuminating the butterflies in the tree.  At first, the butterflies appeared like dead leaves gathered tightly together at the tips of the tree branches.  Their closed wings displayed the darker grays and browns of the undersides of their wings, providing a perfect camouflage.  But as the sun pierced the soft drizzling rain, some butterflies began to open their wings, revealing their brilliant orange, like pieces of stained glass adorning the branches.  A rainbow graced the clusters from above, a precious gift on a chilly 45F morning.

We completed the count from the neighbor's yard, and returned to the grove entrance.  Finally, for the first time this season, some monarchs had moved from the neighbors' yards and clustered inside the grove in good numbers. They had formed clusters midway up in the old Eucalyptus trees lining the grove's edge near the entrance.  The team began counting the monarchs in these clusters.  They started by selecting a large cluster in a single tree. They each counted the monarchs in the cluster, and then compared their findings. They then counted all the other clusters in that tree, agreeing on a final count before moving on to the next tree that contained monarchs.  They made note of the tree species the monarchs were found in, as well as the height at which the clusters were located.

We walked further down the path and located a few additional clusters about 45 feet up in Monterey pine trees overhanging the path, and counted these as well.  From this point in the grove, we could peer through the Eucalyptus trees and see the neighbor's pine tree where we had counted the monarchs earlier.  While the grove was still quite shady, the neighbor's pine tree was in the direct morning sun, though completely exposed to any wind. I wondered aloud as to why they had picked that particular tree.  Could it be the morning sun?  Stong wondered as well.  He said it had been a very cold winter so far this season, with the grove's interior reaching near freezing temperatures.  He and his team had wondered if some of the monarchs were sacrificing a windbreak, in favor of a location in the direct sun.  

We decided to move deeper into the interior of the grove, following trails carved out by the resident deer population.  As we walked, we discussed predation of monarchs by squirrels in the grove. Masotti reported finding 192 monarchs alive on the ground with their abdomens missing, the wings and thorax still intact.  Another 30 monarchs were already dead, their abdomens also missing.  Stong described how the abdomens had been removed with near-surgical precision, leaving some monarchs attempting to fly despite the absence of their abdomens.  The team recalled how they had thought this might be due to attacks by wasps, until they actually witnessed squirrels preying on the monarchs.  Masotti captured photos of a squirrel consuming the monarchs, an unusual behavior given that monarchs have some protection due to their toxicity and bitter taste. Clearly, at least one squirrel in the grove is undeterred by the monarchs' toxicity.

After two hours, we had completed the count.  The final tally was 4520 monarchs. Like PGMS, the team reported that population counts are down this season at most western overwintering sites as compared to last season.  

Our thoughts turned to a discussion of the plight of the western monarch population.  Like the eastern population, the western population has experienced a significant decline over the past two decades, dropping 81% since the late 1990's.  Many monarch enthusiasts are aware that most monarchs east of the Rockies spend the winter in Mexico.  But far fewer people are aware that most monarchs west of the Rockies spend the winter in California.  Bringing public awareness to the plight of the western monarch population is a mission currently being undertaken by many Monarch Joint Venture partners. Research efforts in the west have led to a greater understanding of monarch breeding, migratory and overwintering behavior, as well as the creation and restoration of breeding and overwintering habitat.  If you would like to learn more about the western monarch population, visit The Western Monarch Count Resource Center.  Consider volunteering with one of the organizations involved in western monarch conservation.  Opportunities abound, and your help is greatly needed!


Western monarch butterflies cluster at Pacific Grove Monarch Sanctuary.

See more photos in a photo journey of the count at PGMS by Candy Sarikonda:


Squirrel eats monarch butterfly at PGMS

See more photos and the story of this squirrel eating monarchs at PGMS by docent Connie Masotti:


The Monarch Joint Venture is a national partnership of federal and state agencies, non-governmental organizations, and academic programs working together to conserve the monarch butterfly migration. The content in this article does not necessarily reflect the positions of all Monarch Joint Venture partners. Header photo by Connie Masotti.