Characterizing the Natal Origins and Host Plants of Western Monarchs

Summary

ABSTRACT: The objective of this proposed work is to better characterize the natal origins of western monarch (Danaus plexippus) butterflies using stable isotopes and cardenolides. This work will build on previous studies and may help to explain how the population increased from less than 2000 individuals in 2020 to nearly 250,000 individuals in 2021. Despite their conservation importance and recent population declines, the natal origins of western monarchs remain poorly known. Improving knowledge of these natal origins would inform species protection and habitat management. AWARD ID: F23AC00051 START DATE: 09/16/2022 END DATE: 10/31/2026 SOURCE: Region 8 Science Applications AMOUNT: $22,934 PI: Dr. Louie H. Yang CONTACT [...]

Summary

ABSTRACT:  The objective of this proposed work is to better characterize the natal origins of western monarch (Danaus plexippus) butterflies using stable isotopes and cardenolides. This work will build on previous studies and may help to explain how the population increased from less than 2000 individuals in 2020 to nearly 250,000 individuals in 2021. Despite their conservation importance and recent population declines, the natal origins of western monarchs remain poorly known. Improving knowledge of these natal origins would inform species protection and habitat management.

AWARD ID: F23AC00051

START DATE: 09/16/2022

END DATE: 10/31/2026

SOURCE: Region 8 Science Applications

AMOUNT: $22,934

PI: Dr. Louie H. Yang

CONTACT INFO:  Department of Entomology and Nematology, University of California, Davis,

LEAD ORG: University of California Davis

FWS PROJECT OFFICER: Dr. Matthew P. Dekar

Phase 2 Continuation Funding (FY23)

ABSTRACT:  We propose to monitor populations of two species of early-season milkweeds (Asclepias cordifolia and A. californica) in the Coast Range of California to assess their use by migratory western monarchs (Danaus plexippus). This work will help fill a key gap in our knowledge of milkweed-monarch interactions in the early season, a time when monarch populations are likely at their lowest numbers each year, and when successful reproduction of the first post-winter generation is likely to have especially large effects on subsequent annual population growth. We propose to better characterize the timing, location and extent of early-season milkweed-monarch interactions by monitoring multiple populations of each host plant species each week over three years. The University of California at Davis is located near both the northern range limit of A. californica and the southern limit of A. cordifolia in the Coast Range. We have identified four populations of each milkweed species in research-protected field sites. We propose to hire a full-time seasonal field assistant to visit each of these sites weekly throughout the early season (February-May) for three years (2024-2026). At each site, we will monitor a population of up to 30 milkweed stems for milkweed phenology and monarch breeding, using protocols modified from previous milkweed-monarch studies in this region to quantify the density and development of monarch eggs and caterpillars. This knowledge will allow us to better understand and explain the variability of western monarch populations.

AMOUNT: $117,500

SOURCE: Center for Pollinator Conservation

Characterizing the Natal Origins and Host Plants of Western Monarchs

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