Each year, as the temperatures begin to drop and the milkweed plant—a monarch’s favorite food source—begins to die off, the black-and-orange wings of monarch butterflies (Danaus plexippus) can be seen fluttering as the insects make their way on their migratory path to overwintering sites. In the east, monarchs travel from Canada to Mexico, while western monarchs, found west of the Rocky Mountains, overwinter right here in California from about mid-October to February before returning to their year-round foraging for food.
Unfortunately, that colorful sight is becoming rarer as monarchs’ numbers decline. In 2024, the western monarch’s numbers reached a near-record low, second only to 2020. During the twenty-eighth annual Western Monarch Count, the Xerces Society, a conservation group dedicated to invertebrates, counted just 9,119. That’s a precipitous drop from the more than 200,000 that were counted each year from 2021 to 2023. But what’s so special about the monarch, and what factors are likely contributing to its disappearance from California? What can be done? And how can you get kids involved in learning about monarchs and their importance to the ecosystem? Read on to learn more about this important pollinator species.
Magical Monarchs
Monarch Survival and Climate Change
So what’s contributing to the monarchs’ decline? Scientists report that there isn’t just one culprit, but they point to climate change and the extreme weather it causes as major drivers of the downward population trend.
Climate Change
In California, climate change means not just higher temps but longer, more serious droughts and extended fire seasons that stretch into the winter. These longer fire seasons pose additional risks to species like the monarch, which relies on California parkland for overwintering habitat. Because the monarchs overwinter en masse, concern is mounting that a fire could wipe out an overwintering population.
Heat Waves
Heat waves are dangerous for all creatures, but younger members of a species are especially vulnerable. As they grow, they may not be strong enough yet to find relief from the scorching rays of the sun, or to regulate their behavior to survive in a rapidly changing environment or to fight off parasites and other diseases. As anyone who has seen a dried-out worm on the sidewalk on a summer day can attest, the sun and hot pavement can mean certain death. Extreme heat can kill monarch caterpillars, too, but its effect on milkweed plants has alarmed researchers. A 2018 study found that in extreme heat, an invasive milkweed that monarchs in the southern United States feed on was associated with lower survival rates and body weights. Researchers discovered that the latex the invasive plant produced contained higher concentrations of toxins, throwing off the balance between the monarchs and the host plant it needs to survive.
Habitat Loss
Habitat loss is a source too. Milkweed not only serves as a food source for adult butterflies but is an essential host plant for monarch larvae. Monarchs lay their eggs under the leaves of milkweed plants, and the larvae consume the plant as they grow. Milkweed is toxic, but because monarchs have a special adaptation, they are able to consume it. However, predators who eat the distinctive orange-and-black butterflies become sick, which deters them from further predation. This is one small way nature helps preserve the monarch population, so protecting milkweed-rich monarch habitats is crucial.
What’s Being Done?
The monarch butterfly’s decline is concerning, but it isn’t hopeless. Better tracking measures can help inform public policy, and recently, scientists have been able to improve tracking, which may boost the effort to get monarchs on the Endangered Species List. Outfitted with tiny solar-powered tracking devices, single monarchs can now be monitored on their migration journeys, giving researchers important information about their life cycle and behaviors.
In 2024, the US government was considering adding monarchs to the list of endangered species that would be protected under the Endangered Species Act. It’s unclear whether these efforts have stalled, but adding the monarch to the list would ensure vital conservation of its habitat in the US and could help guide pesticide regulation with the monarchs’ needs in mind.
Monarch Butterfly Activities for Kids
Hatching a single captive butterfly from a caterpillar inside your home may teach kids firsthand about the life cycle of the monarch as it emerges from its chrysalis, but captive breeding and rearing on a large scale can have negative impacts on the population. Research shows that well-meaning captive-breeding efforts pose risks to the wild population and can impede scientists’ tracking and counting efforts. But there are plenty of other ways you can get kids involved! Local parks have kid-friendly programs, or you can sign up the family for a day of counting. Here are a couple of other ideas to get you started:
Visit an Overwintering Site
Even when the numbers are low, monarchs still overwinter, and there are several hot spots for these graceful, brightly colored fliers. The peak season is November to mid-December, but monarchs remain into February. The Xerces Society maintains an interactive map of overwintering sites along the Pacific coast, which you can check out before making a trip. The society recommends sunny mornings when temps are above fifty-five degrees as the best opportunity to see monarchs.
Plant Local California Milkweed
Missed out on the monarchs this season? If you have a green thumb and a little outdoor space to plant it, California milkweed from a local source can help monarchs get the food they need to help offset habitat loss. It’s also a great opportunity to teach kids about monarchs’ food sources and habitat. Check with a local native plant source or native plant society to ensure you’re growing the correct variety for the area. Be sure to keep little ones and pets from eating milkweed, as the plant is toxic to humans and other animals, not just monarch predators.
For more STEM-related activities for kids, sign them up for one of our programs and help sprout your junior scientist’s budding curiosity about the world around them.
Footnotes:
1. Xerces Society for Invertebrate Conservation, “Western Monarch Butterfly Population Declines to Near Record Low,” press release, January 30, 2025, https://www.xerces.org/press/western-monarch-butterfly-population-declines-to-near-record-low.
2. Pollinators—Monarch Butterfly,” National Park Service, accessed December 7, 2025, https://www.nps.gov/articles/monarch-butterfly.htm.
3. “Monarch Importance,” Monarch Joint Venture, accessed December 7, 2025, https://monarchjointventure.org/faq/monarch-importance.
4. Emily Doyle, “Impact of Climate Change on the Western Monarch Butterfly,” California State Parks Foundation, November 19, 2024, https://www.calparks.org/blog/new-analysis-impact-climate-change-western-monarch-butterfly.
5. Liza Gross, “Record-Breaking Heat Waves Add to Risks for Western Monarchs,” Inside Climate News, October 9, 2024, https://insideclimatenews.org/news/09102024/western-monarchs-record-breaking-heat-waves/.
6. “Habitat Needs,” Forest Service, accessed December 7, 2025, https://www.fs.usda.gov/wildflowers/pollinators/Monarch_Butterfly/habitat/index.shtml.
7. USDA Agricultural Research Service, “Milkweed (Asclepias spp.),” June 26, 2018, https://www.ars.usda.gov/pacific-west-area/logan-ut/poisonous-plant-research/docs/milkweed-asclepias-spp/; and Caesweb, “The Connection Between Milkweed and Monarch Butterflies, Coastall Georgia Botanical Gardens," October 2, 2023, https://coastalbg.uga.edu/2023/10/the-connection-between-milkweed-and-monarch-butterflies/.
8. Dan Fagin, “We Can Now Track Individual Monarch Butterflies. It’s a Revelation,” New York Times, November 17, 2025, https://www.nytimes.com/2025/11/17/science/monarch-butterfly-migration-tracking-sensor.html.
9. US Fish and Wildlife Service, “Monarch Butterfly Proposed for Endangered Species Act Protection,” press release, December 10, 2024, https://www.fws.gov/press-release/2024-12/monarch-butterfly-proposed-endangered-species-act-protection.
10. “Joint Statement Regarding Captive Breeding and Releasing of Monarchs,” Xerces Society for Invertebrate Conservation, accessed December 7, 2025, https://xerces.org/monarchs/joint-statement-regarding-captive-breeding-and-releasing-monarchs.
11. Emma Pelton, “Keep Monarchs Wild: Why Captive Rearing Isn’t the Way to Help Monarchs,” Xerxes Society for Invertebrate Conservation, August 16, 2025, https://xerces.org/blog/keep-monarchs-wild.