Reference my earlier post Overwintering Numbers for Eastern Monarch Migration Up. In this post I’m writing that the overwintering numbers for the Western Monarch Migration are alarmingly down. While the Eastern Monarch Migration has declined by more than 80%, the Western Migration has declined by more than 86%.
The Monarchs overwintering in California travel west from Idaho and Utah and north from Canada and along the Pacific Coast to overwinter in the coastal forests. There they nestle in eucalyptus trees. Blue Gum (Eucalyptus globulus) is the predominant Eucalyptus species. They also use Monterey Pines and cypresses, but the Eucalyptus is their preferred roosting tree. Eucalyptus trees flower from December to May, while the monarchs are roosting and when few other sources of nectar are available from native plant species.
Surveys done by volunteers with the Western Monarch Thanksgiving Count found only 28,429 butterflies, an 85.2% fall from the previous year—and a 99.4% decline from the number of monarchs in the state in the 1980s.
The Xerces Society for Invertebrate Conservation has worked with monarch scientists at institutions across the West to develop the Western Monarch Call to Action, a five-point rapid-response action plan to rescue the western population of the monarch butterfly. According to their website, “the call to action is a set of rapid-response conservation actions that, if applied immediately, can help the western monarch population bounce back from its extremely low 2018–19 overwintering size.”
- Protect and manage California overwintering sites — stop the destruction and damage from development and inappropriate tree trimming of the Monarchs overwintering trees. Create and implement a manaagement plan to protect and grow needed habitat for the butterfly.
- Restore breeding and migratory habitat in California — plant early blooming native flowers and milkweed to restore breeding and migratory habitat. They use native host and nectaring plants growing anywhere, i.e., gardens, parks, along railroads, right-of-ways, farms, etc so they can lay their eggs and find nourishment after they leave the overwintering sites.
- Protect monarchs and their habitat from pesticides — seek out and use non-chemical options to prevent and manage pests in landscaping. Stop the use of neonicotinoids in the commercial production of milkweed plants. Suspend or limit the use in croplands and other commercial applications.
- Protect, manage and restore summer breeding and fall migration monarch habitat outside of California — identify remnant areas of native monarch habitat and protect them from development, while at the same time restoring and managing in other areas.
- Answer key research questions about how to best aid western monarch recovery — monitor and research overwintering sites to determine what is causing the decline in the western Monarch butterfly population. Is it Oe? Destruction of Eucalyptos trees? Development? Neonics?
So if you live west of the Rocky Mountains, please make an effort to identify and help enhance habitat across the Western States Migration route so Monarchs have a place to feed and breed.
Click on Western Monarch Milkweed Mapper for more information.