Captive-Raised Monarchs Fail To Migrate

Monarch butterfly on zinnia at Phipps Butterfly Forest, Aug 2017 (photo by Kate St. John)

In case you missed it, a monarch butterfly migration study published in the Proceedings of the National Academy of Sciences in June 2019 has troubling news for those who rear monarchs indoors.

Eastern monarch butterflies, famous for their autumn migration from North America to Mexico, have declined 80-90% in the last 20 years. To help the butterflies many people collect eggs and caterpillars in the wild and captive-raise them to increase their chances of survival. Unfortunately this well-meaning act can damage the insect’s ability to migrate.

Researcher Ayse Tenger-Trolander at Univ. of Chicago stumbled upon this when she purchased captive-bred butterflies for her monarch migration study. To measure their autumn migratory drive she placed them in a flight simulator and noted the dominant direction they wanted to fly. Wild migratory monarchs orient South. The captive-bred monarchs chose random directions, unlikely to migrate.

To further test the butterflies, Tenger-Trolander collected wild monarchs and raised a new generation indoors, mimicking outdoor autumn conditions. Here’s what she found.

Furthermore, rearing wild-caught monarchs in an indoor environment mimicking natural migration-inducing conditions failed to elicit southward flight orientation. In fact, merely eclosing(*) indoors after an otherwise complete lifecycle outdoors was enough to disrupt southern orientation.

Contemporary loss of migration in monarch butterflies, PNAS

Chip Taylor, Director of Monarch Watch, pointed out on NPR that some captive-bred monarchs do make it to Mexico, but added that “The real reason for raising monarch butterflies is for the enjoyment, the education. [T]he idea of individuals saving caterpillars as “monarch rescue” is misguided. “That’s simply not going to work as a way to boost the population,” says Taylor. “What we really need to do is to improve the habitat.”

We’re learning that monarch migration is complex and very fragile. It’s easy to break it in a single generation.

(photo by Kate St. John)

(*) “eclosing” means emerging from the chrysalis.

5 thoughts on “Captive-Raised Monarchs Fail To Migrate

  1. Very fascinating given I raise Monarchs inside. I wonder if you raised them out doors in a protective enclosure would that still disrupt their journey south. And what about Monarchs that are raised indoors early in the summer? This is a very interesting study that I am sure needs more research to guide us into helpful positive results.


  2. That’s interesting, Kate. Basically we should grow milkweed and pollinator flowers and leave the Monarch butterflies alone. However, I think there’s a great teaching opportunity to show children and adults the amazing journey of Monarch egg to caterpillar to chrysalis to butterfly with 1 captive Monarch.

    1. Donna, Chip Taylor of Monarch Watch said the same thing about the educational opportunities. I’ve added his quote from the NPR article to the blog.

  3. I have been in your shoes where I thought I needed to rear every Monarch that I could find to save them. But, that isn’t the case. As I read the research and talked with Dr. Lincoln Brower, the top Monarch scientists, and other scientists, I came to realize that creating habitat everywhere is the key to saving all butterflies and pollinators.

    When I do rear a few inside I use a sunlight lamp. I keep this on during normal daylight hours so that they won’t lose their sense of what season they are in. Light and temperature trigger their migration. Be careful of how cold the area is where you are rearing. I try to keep my rearing area in the upper 70s to low 80s.

    Monarch butterflies are not threatened or endangered as a species. The Monarch Migration is threatened. Monarchs do not need people to mass captive rear them to save them. The key to saving the Monarch Migration and all pollinators is to create habitat, which consist of planting host and nectar plants, also add shrubs and trees for shelter. Dr. Lincoln Brower one of the petitioners on the application for threatened status said that people should limit captive rearing to 100 during their breeding season. Monarch Watch recently posted an update on their tagging to alert people to the fact that reared Monarchs are usually smaller and less successful at migrating.
    “A lot of the rearing appears to be inspired by what could be called “monarch rescue”. It is known and widely reported that 98-99% of all monarch eggs and larvae fail to become adults due to predation, parasitism and other causes. This observation has led many to “save” monarchs by collecting eggs and larvae and rearing them indoors, etc. Aside from enjoying the experience of rearing these interesting butterflies, many justify the practice with the supposition that their efforts are contributing to the population. While there is evidence that some of their efforts result in monarchs reaching MX, the idea that rearing, tagging and releasing monarch will lead to a significant increase in monarch numbers is misguided.”

    Actually the percentage for Monarch survival is 3-10%, but during their life time Monarchs lay hundreds of eggs. There can be up to five to six generations during their breeding season. During this time, one generation builds upon another to end up multiply to thousands of individuals.
    “Are there natural predators that kill monarch eggs, larvae, and adults?
    Yes, the percentage of monarchs that survive from egg to adulthood is very low. Researchers agree that less than 10% of the eggs that are laid survive to become adult butterflies, and some feel that this number may be significantly under 10%. To account for low survival in the wild, female monarchs can lay 300-500 eggs in their lifetime.”

    Rear a few Monarchs for your enjoyment. But, know that captive rearing is not needed to save the Monarch butterfly as a species. The Monarch butterfly species is not threatened or endangered. The Monarch Migration is threatened. “While captive rearing and release has been an important conservation strategy for some species, releasing reared monarchs is not likely to be an effective monarch conservation strategy and could have negative effects. Potential risks include releasing monarchs that are adapted to captive conditions, increasing parasites and disease in wild monarch populations, and making it more difficult to understand natural monarch distributions.
    There is a lack of scientific evidence that monarch rearing actually results in overall population increases, and it is known to carry risks. Many experts do not support large scale captive rearing for conservation purposes. Recommended strategies that do support monarch populations in the long-term include creating or improving habitat, minimizing monarch and habitat exposure to pesticides, and participating in citizen science or other research. However, there is little risk in responsibly raising a few monarchs for enjoyment, education, or citizen science, which can lead to stronger human connections with and better understanding of this amazing species.”

    Keep local populations wild!

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