Are Monarch Butterflies Endangered?

If you're seeing fewer butterflies, you may wonder if monarch butterflies are endangered. See what the experts say about monarch population numbers.

are monarch butterflies endangered?Courtesy Jaclyn Manker
Monarch tagged with a tracker at Cox Arboretum Metropark in Dayton, Ohio

Monarchs are among the most recognizable and best loved butterflies in North America. But you may have noticed fewer of them traveling through your garden over the last few years. Are monarch butterflies endangered?

Monarch Butterfly Population Numbers

It’s true that monarch numbers have declined recently, and that decline is more extreme in some places than others—but, luckily, it’s not all bad news. Researchers split monarchs into two groups at the Rockies: eastern and western. They’re not distinct species, but their migration paths and overwintering habitats differ. And one group may be more robust and healthy than the other.

In the East, monarchs appear to be rebounding for the first time in years. Some researchers counted a 144% increase in overwintering monarchs in late 2018, the highest numbers recorded since 2006. Emma Pelton, a conservation biologist leading the monarch programs at the Xerces Society for Invertebrate Conservation, says, “It’s worth celebrating, but we also have to be really cautious that it was a ‘Goldilocks’ weather year.” Conditions in 2018 were just right for monarchs, which may have caused the bump in their numbers, but it will take a few years to confirm whether the butterfly population is actually on an upswing. Eastern monarch butterflies are not out of danger yet.

Western monarchs didn’t share their eastern cousins’ success last year—their numbers have been dwindling since the 1980s, when their wintering population was 4.5 million. In 2018, fewer than 29,000 wintered there. That means for every 160 monarchs in the West 40 years ago, there’s only one today.

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Reasons for Monarch Optimism

But there’s reason to hope for West Coast monarchs. The Xerces Society and other organizations with similar goals are pushing to restore and protect overwintering, breeding and migration habitat throughout the West and into Mexico. And they may have Mother Nature on their side. Rain in early winter of 2018 caused a colorful “super bloom” in the Southwest in 2019. The unofficial term refers to a recent burst of California poppies and other native wildflowers. “There’s been just an explosion of flowers,” Emma says. Biologists aren’t sure how many monarchs benefited from the blooms, but some butterflies that overwintered in Southern California probably passed through the area.

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A monarch caterpillar crawls across a milkweed leaf.Courtesy Jenny Miner
A monarch caterpillar crawls across a milkweed leaf.

How to Save Monarch Butterflies

Weather plays a large part in conservation, but there’s plenty gardeners can do to help, too. Planting natives and choosing natural control solutions for weeds and pests go a long way in sustaining the beloved monarch. All monarchs start their lives on milkweed; it’s the only plant on which adults lay their eggs and caterpillars happily munch. Consider planting one of the many local varieties of milkweed in your garden to get an up-close view of their life cycle.

Support adult monarchs on their long journey south by growing nectar-rich flowers that bloom from late summer into fall. And be mindful when using insecticides and herbicides, which are strongly linked to insect and pollinator declines. “People may not see monarchs this year in the West,” Emma says. But monarch butterflies are not endangered yet. She urges everyone to be patient for their return and to keep an eye out for other pollinators.

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Rachel Maidl
Rachel Maidl is a senior editor for Birds & Blooms magazine. She enjoys bird-watching in her urban backyard and local state parks, gardening for pollinators and researching new plants. Her favorite backyard visitors are the bumblebees that visit her sedums.