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Issues Of The Environment: Protecting The Future Of Monarch Butterflies

Monarch Butterfly
Wikipedia Media Commons

Over the past 30 years, there has been more than a 90-percent decline in the numbers of monarch butterflies, and much of that can be attributed to loss of habitat.  There is ongoing consideration of adding them to the endangered species list, and, in "Issues of the Environment," 89.1 WEMU’s David Fair explores what that means to humans and our ecology in a conversation with the David Clipner, the Director of Education and Wildlife at the Leslie Science and Nature Center in Ann Arbor. 


  • The 2018/19 overwintering population of monarch butterflies was the highest it has been in 12 years, so the 2019 monarch migration northward started out well.  (The population has been in a fairly sharp decline for the past 30 years.) 
  • In addition, the US Fish and Wildlife Service is in the process of determining if the monarch will be placed on the endangered species list.  The listing should be proposed by 2021, and then they have a year to review, so effective in 2021. 
  • There are a couple of new recommendations for best practice for citizens wishing to help monarchs.  Monarch Watch has discovered that wild monarch butterflies are more likely to reach the wintering grounds in Mexico than monarchs raised indoors.  Monarch Watch says capturing butterflies for tagging provides more valuable data than for butterflies reared indoors.  The second new recommendation comes from Michigan State University, which discovered that new monarch shoots are better for monarchs to lay eggs on.  They are recommending that later in the summer milkweed is mowed down and allowed to regenerate becauase the older shoots don’t support eggs and caterpillars as well as new growth.
  • Leslie Golf Course and Huron Hills Golf Course are also part of the “Monarchs in the Rough” program that works with Audubon International, the Environmental Defense Fund and dozens of golf courses nationally to help the butterflies breed, grow, and successfully migrate.
  • David Clipner, Director of Education and Wildlife for Leslie Science and Nature Center in Ann Arbor, educated the public about how to help monarchs.  LSNS does a great deal to support the monarch populations in our region.  They hold an annual Monarch Migration Festival(Sunday, September 8th, 1:00-3:30 PM), and coordinate events for Monarch Watch---volunteers tags and releases wild and reared monarch butterflies in the hopes that they will be recaptured to learn more about the population. 

What's the big deal about Monarch migration?

Monarchs are important pollinators in many ecosystems from Canada to Mexico.  As the adults move from plant to plant eating nectar from the flowers, they spread pollen that allows the flowers to produce seeds and fruits. These seeds and fruits are essential to the survival of other animals and plants--even humans!

In the last 30 years, monarch populations have declined for several reasons.  In some cases, poison chemicals (called herbicides) used to kill weeds on farms have also killed milkweed plants—the only food source for monarch caterpillars (also called larvae).  When monarchs migrate south, they winter in large trees and forests. Logging and forest destruction in their wintering habitats means that there are less warm, predator-free places for monarchs to live.  The destruction of food sources and habitat, along with a rise in parasites and new predators, have all contributed to the decrease of the monarch population.

Monarchs living east of the Rocky Mountains winter in Mexico and then head north in the spring to lay their eggs in the Southern United States.  It is the young of these butterflies that continues the migration into the Northern US and Canada to lay eggs and start another life cycle.  Given the wide range of communities where monarchs find habitats and food on their journeys, conservation efforts to plant more milkweed and other pollinator plants, and to release captive-bred butterflies are happening on an international scale to try and restore the monarch population.  You can join the effort at LSNC, and even plant a native pollinator garden in your own yard or neighborhood.

Join international conservation efforts, Sunday, September 8th, 1:00-3:30 PM and celebrate the incredible monarch butterfly at the Annual Monarch Migration Festival!  Register ahead of time to release a tagged butterfly in LSNC's pollinator garden and sponsor the migration of additional butterflies to maximize the impact of this exciting project.

Registration is required by Friday, September 6th.  Register for this event online, or call 734-997-1553. 

LSNC works to coordinate our monarch conservation efforts with Monarch Watch.  We encourage you to do the same by visiting their website and taking action.

2018/19 Overwintering Population Nearly Double 2017/18

The overwintering population on monarchs was nearly double what it was last year, and it was the highest it has been in 12 years.

The U.S. Fish & Wildlife Service has announced that they’ll determine whether by December, 2020, whether monarch butterflies should be proposed for listing on the Endangered Species List.

If the Fish & Wildlife Service decides monarchs should be proposed as endangered or threatened, they will publish a proposed rule in the Federal Register, invite public comment and engage in further analysis before deciding whether listing is appropriate.  According to the Fish & Wildlife Service, they would have up to one year after publishing a proposed rule to make a final decision, thus it could be December 2021 before a final determination is made.  Only at that point would the monarch’s status be decided.

The U.S. Fish and Wildlife Service is a bureau of the Department of the Interior.

Monarch Watch

Tagging wild and reared monarchs: Best practices

9 July 2019 | Author: Monarch Watch

Greetings taggers and welcome to the 2019 monarch tagging season.  This year marks Monarch Watch’s 28th season!  Over the years, thousands of taggers have contributed to our tagging database.  It is an enormous record and a veritable gold mine of information about how the migration functions.  The record represents at least 1.8 million tagged butterflies and lists where, when and by whom each butterfly was tagged.  The sex of each butterfly and whether the butterfly was wild–caught or reared, tagged and released is also recorded. These data have told us a lot about the migration.  Yet, this record could be improved but we need your help.  Diving into the data has revealed a number of surprises such as the difference between the probability that a reared monarch will reach Mexico and the probability that a wild–tagged monarch will do so.  The recovery rate is higher for wild caught monarchs (0.9% vs 0.5%) and it is the data from the wild–caught butterflies that tell us the most about the migration.  Frankly, for some analyses, we have to set the reared monarch data aside. That doesn’t mean it is not valuable, but its uses are limited.

Given the difference between the recovery rates of wild–caught and reared monarchs, what are our goals going forward?  For wild–caught monarchs, we have several goals.  First, we need to increase the number of taggers from western Minnesota and Iowa westward into Nebraska and the Dakotas.  This region is known to produce large numbers of monarchs and those tagged have high recovery rates.  Increased tagging in this area will give us a more complete understanding of dynamics of the migration.  Second, we need to increase the number of wild monarchs that are tagged since these provide the most valuable data.  Third, we need to increase the number of taggers who tag from the beginning of the tagging season in early August until the migration ends.  Tagging records for the entire season will help us establish the proportion of the late–season monarchs that reach the overwintering sites.  When tagging wild–caught monarchs, many taggers run out of tags well before the season ends.  That’s great, but it would help us to know when all tags had been used by indicating this via the online tagging data submission form.

For those of you who prefer to rear, tag and release, we have a few suggestions as to how you might improve the odds that your reared monarchs will reach the overwintering sites in Mexico.  But, it is more than reaching Mexico. The best outcome for a wild monarch is to survive the migration, the winter conditions, the flight north in the spring and to successfully reproduce in Texas in the spring.  It seems reasonable that this should be the goal for those who choose to rear, tag and release.  To reach that goal, we have to know something about the wild monarchs that allows them to survive.  The migration is a strong selective force. It eliminates the weak, those with diseases, the undersized and those with genetic and other deficiencies. It also eliminates those that have not received the environmental cues that properly trigger diapause and the orientation and directional flight characteristics of the migration.  One way to increase the success rate for reared monarchs is to rear monarchs in a way that maximizes their exposure to environmental changes (day/night temperatures, changing photoperiod with the ability to sense sunup and sundown, etc.) that occur in the fall. In other words, rearing outdoors, on porches, in pole barns, open garages, etc., would likely produce better results than rearing in an air–conditioned kitchen, spare bedroom or similar space.

As to the actual rearing, raising the monarchs on living plants–potted or in the ground–is likely to produce the largest monarchs, provided that the monarch larvae have an abundance of foliage to feed on at all times.  Cut foliage in the form of leaves also works well, but the leaves have to be fresh and abundant relative to the numbers of larvae in each container.  Containers should be cleaned each day once the larvae reach the 4th instar.  To avoid passing the monarch disease Ophryocystis elektroscirrha (O.e. or OE) from outdoor monarchs to reared monarchs, both the living and cut foliage can be sanitized using a 10% bleach solution with a drop or two of liquid soap added.  After soaking in the bleach solution for two minutes, the leaves should be rinsed thoroughly with clean water and patted dry before being fed to larvae.  Living plants can be sprayed with the bleach solution and then rinsed.  If you are using cut stems with leaves intact, they can be cleaned the same way.  In that case, be sure to cut the stems under warm water before placing them in vases, etc.  The warm water keeps the latex vesicles from closing down the transport of water to the leaves.  Cut stems work to feed larvae, but they can go limp and be less suitable as a food source than cut leaves.

We are offering these suggestions since reared butterflies tend to average smaller than wild migrants.  That difference can be reduced significantly if careful attention is given to rearing larvae under the best possible conditions.  Large monarchs have the best chance of reaching Mexico, surviving the winter and reproducing in Texas.  There are several reasons for this: better glide ratio, better lift with cross or quartering winds, larger fat bodies, more resistance to stress, etc.  There are very few small monarchs among those that return in the spring.

To summarize:

1. Rear larvae under the most natural conditions possible.

2. Provide an abundance of living or fresh–picked and sanitized foliage to larvae.

3. Provide clean rearing conditions.

4. Plan the rearing so that the newly–emerged monarchs can be tagged early in the migratory season (10 days before to 10 days after the expected date of arrival of the leading edge of the migration in your area*).

5. Tag the butterflies once the wings have hardened and release them the day after emergence if possible.

6. When it comes to tagging, tag only the largest** and most–fit monarchs.  Records of tags applied to monarchs that have little chance of reaching Mexico add to the mass of tagging data, but do not help us learn which monarchs reach Mexico – unless the measurements, weight and condition of every monarch tagged and released is recorded.  There are a few taggers who keep such detailed records and those data can be very informative.  If you collect such data and are willing to share it please contact us; do not add this information to the standard tagging datasheet.

As a final note, this text is not a directive.  We are not telling you what to do; rather, we are simply providing suggestions that may lead to more successful rearing and tagging efforts.

*Migrations seem to move in concert with the declining sun angle at solar noon (SASN).  The fastest migrations have a leading edge of 57 degrees.  Therefore, “early” is defined as 10 days either side of when the sun angle at solar noon reaches 57 at your latitude.  To determine SASN for your latitude, visit suncalc.org.  A table of SASN values by latitude and/or further information will be posted at a later date.

**The easiest way to judge the size of your monarchs is to measure the forewing from the base to the apex of the wing (Figure 1).  These measures range from 46–52 mm with most migratory monarchs measuring 49–51 mm. After some experience with both wild and reared monarchs, it is relatively easy to judge those that are below 49 mm.

For years, lovers of the orange and black monarch butterflies that make Michigan home in the spring and summer have planted milkweed to help the declining species along. In an odd quirk, milkweed is the only plant monarch caterpillars eat, and the plant's broad leaves are sought out by the butterfly for egg-laying.

New research out of Michigan State University, however, says monarch-lovers should consider chopping down at least some of their milkweed plants later in the summer.

"From a monarch's perspective, they need milkweed, but not all milkweed stems are equal," said Nate Haan, a postdoctoral research associate in MSU's Department of Entomology.

"When they are flying around looking for the best places to lay their eggs, they are seeking out younger, more tender stems that haven't flowered yet.  As summer progresses, those stems get more and more hardened."

Haan's research, published in the peer-reviewed, scientific Journal of Biological Conservation, shows that mowing a third of milkweed patches in June and July, respectively, resulted in more monarch butterfly eggs laid on the regenerating milkweed than on the remaining, undisturbed third of milkweed plants.

"Milkweed is really robust," he said. "If you chop some down in the middle of summer, in a couple of weeks it will send up new shoots."

It's a phenomenon that has been observed for generations, Haan said — "even some observations going back to the 1800s that after hay fields got harvested, the fields got mowed, and the milkweeds that came back up had a lot of monarch eggs on them."

But no one had ever tested the anecdotes in an empirical study before, he said.

The mowing has an added benefit, Haan said.

"Monarch eggs and caterpillars get eaten by predators such as ants and spiders," he said.  "We wondered if the disturbance of the milkweeds would also knock back predator populations, providing a window in time where predators are less abundant and the eggs and caterpillars are better allowed to thrive. We found that was the case, too. It takes a few weeks for the predator populations to build back up" after a milkweed mowing.

This process happened naturally for most of the 20th Century, as milkweeds typically grew in agricultural fields and were taken down during mechanical harvesting, Haan said. But changes in the types of herbicides farms use have all but wiped out milkweeds in the fields, he said.

The monarch butterfly is unusual.  It's the only known butterfly to make a two-way migration to a warmer, Southern winter home, as migratory birds do.  Butterfly generations typically live about two to six weeks, with Michigan seeing about two or three generations of monarchs beginning in May and lasting through the summer.  But the last generation, around September, survives longer, making the long journey to an area of Mexico where millions of monarchs overwinter.

When spring comes, so does the northward trek, with several generations of monarch butterflies living, breeding and dying, as they make their way back to their summer habitat throughout the northern U.S. and southern Canada.

The population in recent years has suffered a disturbing decline, with only 1.7 acres of their Mexican winter grounds covered in the winter of 2013-14.  Weather, pesticides and habitat destruction are suspected factors.  The last few years, however, monarchs have made a comeback, with this winter in Mexico the best in at least a decade — almost 15 acres of monarchs.

MSU researcher's tips for helping monarch butterflies thrive in Michigan:

Plant milkweed, which is vanishing in its typical, natural habitats.  "The more milkweed we plant, the better," said Nate Haan, postdoctoral research associate in Michigan State University's Department of Entomology.  Seeds for milkweed plants native to Michigan can be purchased online or at some local greenhouses.

Don't misuse his research.  Haan doesn't want people taking a lawnmower to the entirety of their milkweed stands this summer.  Instead, use a weed whip to take down about one-third of an area's milkweed plants around mid-June; then do the same to a different third of the plants in mid-July.  "What I guess will happen, on that new growth, is you'll see a lot more eggs and caterpillars," he said.

Golf Course Program for Monarchs in Ann Arbor

The “Monarchs in the Rough” program that works with Audubon International, the Environmental Defense Fund, and dozens of golf courses nationally to help the butterflies breed, grow, and successfully migrate.

Monarch butterflies lay their eggs on milkweed and have experienced a 90-percent decline in population in the last 30 years, said Doug Kelly, director of golf for Huron Hill and Leslie Park.  Huron Hills and Leslie Park golf courses are growing the plant in large patches and across hills outside of their playing areas.

Golf courses get a bad reputation for being a ground of chemicals, but those in Ann Arbor are environmental stewards, Kelly said.  The Huron Hills and Leslie Park courses also have bat houses, mallard nesting in ponds and turtle nesting grounds, he said.

“We love that the program focuses on the golf industry because golf courses represent some of the last large green spaces,” he said.  “Farm lands and acres are being gobbled up for residential development and we have some of the last remaining spaces. Any environmental initiatives will be helpful.”

While the plants aren’t in bloom yet, there are several eggs, caterpillars, and monarch butterflies around the course.  The milkweeds and wildflowers are expected to be in full bloom by August, Kelly said.

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— David Fair is the WEMU News Director and host of Morning Edition on WEMU.  You can contact David at734.487.3363, on twitter @DavidFairWEMU, or email him at dfair@emich.edu

Contact David: dfair@emich.edu
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