Is Captive Rearing Hurting Monarchs?

Experts say captive rearing—or raising monarchs indoors—poses risks to the butterflies, from disease to decreased fitness

By Elizabeth Anne Brown
Conservation
Mar 26, 2026

A radio-tagged monarch alights on common milkweed (above). Planting such native milkweeds is a wiser way to help than indoor rearing (below).

MONARCH BUTTERFLIES BOAST ONE OF THE MOST DEVOTED human fan clubs of any animal species—so devoted, in fact, that some welcome the butterflies into their homes. Each summer and fall, thousands of well-meaning people scoop up the squishy striped caterpillars in their yards to raise from chrysalis to butterfly indoors or even order eggs online from commercial breeders. But scientists warn that these efforts to “help” monarchs, when practiced at large scale, may do far more harm than good.

Each fall, millions of the butterflies east of the Rocky Mountains depart breeding grounds in the eastern United States and southern Canada to undertake a marathon migration to mountainous south-central Mexico—a journey that can total up to 3,000 miles. Most monarchs west of the Rockies embark on a similar, if shorter, fall migration from western states to coastal California.

Despite weighing less than a paper clip, these delicate insects brave storms and exhaustion to reach refuges where warmer temperatures and tall trees provide protection from harsh winter weather—and provide researchers an annual opportunity to estimate the butterfly’s numbers. Over the past few decades, they report that those numbers have plummeted, attributing the declines to the combined threats of climate change, pesticides and habitat loss.

While scientists say the species Danaus plexippus is not at risk of global extinction, its North American migratory populations—along with the spectacular long-distance migration itself—are indeed in danger of disappearing. Beyond the butterfly’s precipitous population declines, there are “more and more sedentary monarchs that have stopped migrating,” says Marcus Kronforst, a University of Chicago evolutionary biologist who studies the insects.

Climate change is likely one contributing factor, but indoor rearing of monarch caterpillars also may be sabotaging the migration. Intended to help the larvae escape predators and parasites, the practice is popular in homes and garages across the country.

Yet rearing even wild-caught monarchs indoors seems to dampen their instinct to migrate, Kronforst says. He and his team are studying what cues from the environment—perhaps falling temperatures or dwindling daylight hours—signal to the butterflies that it’s time to take wing. “When you raise them indoors, many of them are confused in some way. They just are not very effective at migration,” Kronforst says. He and his colleagues have found that captive-raised butterflies seem to have a harder time orienting south in fall.

An image of monarch butterflies emerging from chrysalises in a butterfly raising habitat.

According to University of Georgia animal ecologist Andy Davis, who has studied monarch migration for decades, wild monarchs raised indoors also appear to have lower physical fitness. “They’re not as strong physically, and they usually have wings that are smaller and paler in color—both signs of poor migration ability,” he says.

Commercially bred monarchs fare poorly as well. After dozens of generations in captivity, the insects effectively become domesticated, Kronforst says. His research reveals that captive-bred monarchs have smaller, more rounded wings and struggle to orient south even when raised outdoors. Some commercial populations are so turned around that the scientists describe them as “nondirectional.”

Even if indoor-reared monarchs complete the migration, “captive propagation disrupts the natural gene flow that sustains populations and promotes their adaptability,” says Rebeca Quiñonez-Piñón, senior scientist for the National Wildlife Federation. “The greatest concern is the potential harm to the species’ genetic integrity that may result from intentional or accidental selection of traits that do not enhance survival in the wild.”

Raising monarchs indoors also can trigger the spread of Ophryocystis elektroscirrha (OE), a deadly single-celled parasite. “If it doesn’t kill them outright as larvae or pupae, [OE can] make the monarchs’ wings flimsier and more brittle,” Davis says, calling OE “a death sentence during the migration.” (See NWF’s latest guidance on monarch rearing.)

To truly help monarchs, NWF recommends restoring the species’ habitat by cultivating the native nectar plants butterflies need—especially those, such as goldenrod and aster, that bloom during fall migration—as well as the milkweed plants that are monarch caterpillars’ sole food source.

But be careful about what kind of milkweed you choose. Although more than 70 milkweed species are native to the United States, the easiest to get online or in stores is often tropical milkweed, which hails from South America and the Caribbean. “Tropical milkweed doesn’t die back by fall the way native milkweeds do,” says NWF’s naturalist, David Mizejewski. “Because [the butterflies] still have a food source, it can halt monarch migration.” Tropical milkweed also can act as a reservoir for OE spores. Milkweeds native to your area “are the milkweed species that monarchs locally have coevolved with,” Mizejewski adds. (Find and purchase species of milkweeds native to your region.)

Experts say the best way to help monarchs is to tackle the big problems: pesticides, climate change and habitat loss. Lobbying your homeowners association to cut back on pesticides may not be as inspiring as watching a butterfly emerge from its chrysalis on your kitchen table. But the monarch migration will not be saved by the “warm, fuzzy feelings” we get from helping only in ways that are fun for us, Davis says.

Quiñonez-Piñón agrees: “Let’s pour our hearts into true conservation, protecting monarchs’ habitats and ensuring their freedom to migrate—an irreplaceable miracle.”

Elizabeth Anne Brown is a New Jersey-based journalist.