Raising Monarchs at Home—More Harm Than Good?
The monarch butterfly (Danaus plexippus) is renowned for its black and orange beauty and its spectacular migration of thousands of miles to overwintering grounds in California and Mexico. Many of us have been treated to observation of its metamorphosis: from pin-head-sized egg to chunky black, gold, and white striped caterpillar, to green and golden-tinged chrysalis, to the distinctive winged adult. Though we might have observed this process in nature, it is also popular to move monarch caterpillars indoors to observe the transformation. We place them in a clear container and ply them with their food of choice—milkweed (Asclepias spp.). We watch the caterpillars hang in a J shape, turn into a hardened chrysalis, and, after about 14 days, emerge as a winged adult. After releasing the butterfly into the wild, we might feel we have protected and aided a small portion of the monarch population. However, recent findings suggest that this practice may not actually be beneficial for them.
Why worry about monarchs?
Monarch butterflies give us plenty to worry about, both on a small and large scale. The caterpillars are preyed on by other insects, birds, and even their own species. At their very early stages, the tiny caterpillars can even be killed by the toxin in milkweed—a substance that later protects them if they survive the earliest bites. Parasites, bacteria, viruses, and pesticides cause more casualties. Many are dismayed to find monarch chrysalids that at first appeared healthy being eaten from the inside by tachinid fly larvae. All of this means that fewer than 10% of monarch eggs survive to adulthood.
Though insect populations commonly fluctuate, most of us are familiar with news of declining monarch populations. The World Wildlife Fund reported that the overwintering acreage occupied by eastern monarchs declined by 59% in the 2023 to 2024 study year. The Western Monarch Count conducted by the Xerces Society for Invertebrate Conservation reported a slight decline in western monarchs overwintering in California in late 2023. Most disturbing is the evidence from the Xerces Society that western monarch populations are currently at about 5% of their numbers in the 1980s.
Monarch Caterpillars Need to Metamorphose in the Wild
Given all the perils in the wild, it's easy to understand why monarch advocates would want to safeguard monarch caterpillars as they transform. But, in 2015, a group of scientists, including entomologists, ecologists, and monarch researchers, issued a Joint Statement Regarding Captive Breeding and Releasing Monarchs. Here is an overview of the main points pertaining to the general public:
- Raising monarchs in captivity makes conditions more favorable for disease to spread.
- Monarchs raised in captivity may be inferior to those that survived in the wild. Research has revealed that they are less likely to survive migration, and the females lay fewer eggs.
- Eventually, the rearing of monarchs in captivity may cause the insects to be unable to adapt to natural conditions and result in a loss of genetic diversity.
Much of the Joint Statement addresses large-scale rearing of monarchs for purposes such as butterfly releases at events or even to supply well-meaning members of the general public who raise large numbers of monarchs at home. In these conditions, the spread of disease and pathogens is especially likely. In addition, large-scale releases of captive monarchs may throw off efforts to research natural monarch populations.
Responsibly Raise Monarchs as a Teaching Tool
Bringing monarch caterpillars indoors to watch their metamorphosis is a valuable tool to foster an appreciation of the natural world, especially among children. The Xerces Society recommends that an individual rear no more than ten per season. The caterpillars you raise should be from your environment and released there. Here are instructions from Monarch Health on how to responsibly raise monarchs.
How can I help monarchs?
Many questions remain about what is causing the decline in monarch populations. Discussions continue about whether the solution is more milkweed or more nectar plants, in addition to broader questions about our landscape, the use of pesticides, and climate change. Education and contributions to research may be the best ways to help. Consider supporting a citizen-science effort such as Monarch Larvae Monitoring or Monarch Nectar Plant Observations, or contact your county Master Gardener program to learn about efforts in your community.
More information about planting to support monarchs:
