Since 2023, the Monarch Joint Venture (MJV) has been deploying seasonal field technicians across California to document monarch breeding habitats on Bureau of Land Management (BLM) lands. This three-year initiative, Pollinator Habitat and a Changing Climate: Long-Term Monitoring on BLM Lands (L22AS00213), aims to deepen our understanding of Western monarchs to understand when, where, and how monarchs use BLM lands. Additionally, it underscores the vital role of public lands in providing habitats for monarchs and countless other species.
Join us as we dive into the recent adventures of field technicians Anna and Maya, who have been on the ground, collecting invaluable data and witnessing the vibrant biodiversity of California.
Notes from the Field by MJV Field Technicians Anna Haggenjos and Maya Clark
Over the past three months, we've journeyed through California's BLM field offices, starting from the southern deserts and moving northward to the mountainous regions. This trek has exposed us to a rich diversity of blooming plant species and insects. Our survey timing has coincided perfectly with the blooming period of many wildflower species, including several types of milkweed. By monitoring nectar resources and host plants critical to monarch survival, we've gathered essential data on the habitat suitability of these regions.
So far this season, we have discovered 46 monarch caterpillars in each instar. An instar is the period between each shedding of the skin or molt. Monarchs undergo five larval instars, growing up to 2,000 times their original mass. We've observed younger instars feeding and sheltering within fresh milkweed buds, while older instars predominantly consume the buds and larger leaves. These observations highlight the importance of healthy, blooming milkweed plants for the growth of monarch caterpillars.
Milkweed Species and Caterpillar Counts
Throughout our surveys, we've identified eight species of Asclepias (milkweed):
Southern California Desert: Desert (A. erosa), Rush (A. subulata), White-stemmed milkweed (A. albicans).
Central California Grasslands, Forest Edges, and Roadsides: California (A. californica), Heartleaf (A. cordifolia), Narrowleaf (A. fascicularis), Woollypod milkweed (A. eriocarpa).
Northern Field Offices: Heartleaf (A. cordifolia), Narrowleaf (A. fascicularis), Showy (A. speciosa), Woollypod milkweed (A. eriocarpa).
Here’s the breakdown of our caterpillar findings:
California milkweed (A. californica): 30 caterpillars
Woollypod milkweed (A. eriocarpa): 11 caterpillars
Heartleaf milkweed (A. cordifolia): 4 caterpillars
Narrowleaf milkweed (A. fascicularis): 1 caterpillar
Native Wildflowers and Species Diversity
In addition to milkweed, we've encountered a variety of native wildflower species, including superb mariposa lily (Calochortus superbus), purple fairy lantern (Calochortus amoenus), toothed calicoflower (Downingia cuspidata), cutleaf indian paintbrush (Castilleja lacera), and california damasonium (Damasonium californicum), among many others. The diverse species and valuable habitats we've documented during our surveys have been truly awe-inspiring.
Acknowledgments
We extend our heartfelt thanks to the California BLM staff for their continued support, guidance, and expertise. Maya and Anna would like to specifically thank the following individuals they worked with during their field season:
Russel Namitz, Carrizo Plains’ Wildlife Biologist
Aubrie Heckel, Ford Ord’s Botanist
Ismael Ramirez, El Centro’s Natural Resource Specialist
Justin Saiz, Needles' Wildlife Biologist
Landon Eldredge, Mother Lode’s Biologist
Your knowledge, enthusiasm, and dedication to these beautiful regions have been instrumental in our work.
