I spent this past summer rearing and then releasing monarch butterflies back into the wild where they could join the annual fall migration to their wintering grounds in Mexico. In all, I reared 5 monarchs–two out of three from eggs and three out of four caterpillars for a success rate of 71%–far better than the 10% survival rate of monarchs in the wild.
Rearing and releasing five monarchs is a modest accomplishment, especially when compared to other butterfly enthusiasts in the area. I know of who have reared and released 50 or more each. But it is interesting and fascinating and a small step in restoring the eastern monarch population.
The monarch rearing pastime/obsession began innocently enough when, on July 23, I discovered a monarch egg on a common milkweed plant (Asclepius serica) growing in my prairie garden. I had seen a female monarch–more about how to tell the sexes apart later–visit this plant a day or two earlier, knew what her egg would look like, and where to look for it–all thanks to MonarchWatch.org.
The Threats to Monarchs
Monarchs ( Danaus plexippus) ) have always hung out in our garden and we have seen caterpillars in the past but have never observed a chrysalis or butterfly emergence in the wild. The caterpillars we have seen are usually here one day and gone the next–victim to disease or predators, or just moving around? Estimates are that in the wild only 1o% of monarch eggs go on to produce a butterfly. There are so many things working against them: ants eat the eggs, parasitic wasps prey on the caterpillars; tachind flies, nuclear polyedrosis virus, trichogramma wasps, dehydration, and katydids, and praying mantis also are threats.
The list of threats to monarchs goes on: climate change, loss of habitat, including nectar sources for the butterfly and especially milkweed–which is the exclusive food source for the caterpillar–from farm fields and roadside ditches along its migratory route, and the shrinking of over-wintering habitat in Mexico. It all adds up to a dim outlook for the monarch.
The Natural Resources Defense Council (NRDC) estimates that on average 350 million monarchs make that annual migration. Twenty years ago one billion monarchs overwintered in the mountain forests west of Mexico City; but in the winter of 2014-15 that total had shrunk to 56 million monarchs–a decrease of 85%. Fewer than twenty years ago the forest area that sheltered monarchs last winter was an estimated 45 acres; this past winter the monarchs were sheltered in 1.65 acres. The monarch forest habit has protected status but enforcement is spotty and difficult and as a result logging continues.
Given the odds against the monarch we decided to step in and join the hundreds of others across the country who are rearing monarchs, creating habitat, talking to civic groups, planting milkweed, giving caterpillars and chrysalis to school kids, tagging monarchs, and doing many other things to aid their survival.
Humans Can Help by Rearing and Releasing Monarchs
Rearing monarchs is fairly easy and inexpensive. All it takes is daily access to fresh leaves from milkweed plants, a plastic ice cream container or similar (an aquarium with a screen cover works nicely) to house the caterpillar and then chrysalis, a little flat surface area in an office or den, and a few minutes each day for two weeks to tend the caterpillars. From egg to butterfly ready to be released, the monarch’s complete metamorphosis takes about 31 days.
One other thing: like cleaning the kitter litter, don’t forget to each day replace the paper towel with a fresh moistened one and dispose of the frass. Caterpillars produce prodigious quantities of this stuff as they eat milkweed leaves nearly non-stop for two weeks. A build-up of frass can lead to diseases that can infect the caterpillar.
About half way through the summer I ordered a proper rearing and observation chamber from Bioquip products in California. It is a 2′ X 3″ netted structure with a zippered opening like on a tent. But something like this is not necessary unless you plan to go into mass production of butterflies.
I took the milkweed leaf–egg and all–inside and put it in a plastic sherbet container; added a moistened paper towel to keep the leaf alive and humidity up. Three days later, right on schedule, the egg hatched and produced an itsy-bitsy caterpillar. I was hooked and designated this one as egg #1.
My first butterfly release (a male, from caterpillar #1) spent 3 days as an egg; 16 days as a caterpillar; and 12 days as a chrysalis. The butterfly emerged from the chrysalis at 12:30 pm on August 23, 31 days after I began rearing the egg on July 23. It was released late that afternoon. My last butterfly, Lolita (#7) took 37 days, spending 17 days as a caterpillar and 17 more in the chrysalis phase. Lolita was released on October 3, rather near the tail end of monarch migration but with enough time to get to Mexico.
Encouraged by this early success with hatching and keeping a baby caterpillar alive, a few days later I searched for, and found two more eggs ( #2 and #3) on milkweed plants in my garden and placed them in individual rearing containers. Later in the summer I found several caterpillars on milkweed plants in my prairie garden and took these inside for rearing.
To learn more about rearing monarchs, I consulted with my friend David Thompson, an experienced monarch hand and got some good common sense and practical tips. I also relied upon MonarchWatch.org, a non-profit run out of the University of Kansas, for lots of information about the monarch life cycle, their habitat and food needs, and migratory route.
One of the most amazing things about the monarch is this migration.
For example, monarchs that you see in early spring and summer have a life span of nine days and spend it all in the US. However, the monarchs that my friends and I released this late summer have a life span of nine months. These are the ones that will fly to Mexico–to a place they have never seen, along a route they have never flown–and overwinter in the mountain forests. Come spring they will fly north to the southern US and begin the cycle all over. Then their great, and great-great grandchildren will then begin the migration to Mexico next fall.
Netting and Tagging
For scientists to learn more about the monarch migration it is important to keep track of a representative sample of the butterfly population. To this end Monarch Watch issues little non-GPS tracking tags to monarch enthusiasts. Organizations such as the Madison Audubon Society, at its Goose Pond Sanctuary, capture, tag, and release monarchs that are headed to Mexico. The tag’s unique number is reported to Monarch Watch and if observers along the migratory route spot a tagged monarch they can report its sighting to Monarch Watch.
To see how the monarch netting, tagging, and release is done, we traveled on a Saturday morning in early September to the Richard Bong State Recreation Area in SE Wisconsin for a “Migrating Monarchs” field trip sponsored by the Natural Resources Foundation of Wisconsin. Here we would learn more about the monarch life cycle and get first hand experience in netting, handling, and tagging monarchs.
I am already making plans for next year’s monarch project. I plan to rear and release many more butterflies than this year. To feed them, and to attract monarchs to the yard, I am planning vast quantities of milkweed–common, marsh, whorled, and butterfly milkweed–in my prairie gardens. Also going into the gardens are nectar plants for the butterfly–lots of native asters, and blazing stars for example. Tagging monarchs will also be part of the plan. Stay tuned for details.