Sunday, September 8, 2019

A Good Year For Monarch Butterflies

monarch pupates in the relative safety of a firewood pile by Richard Gast If you’ve noticed a lot of monarch butterflies (Danaus plexippus) lately, you’re not alone. From my own observations and from what people have been telling me, this summer appears to have been a very successful one for them; at least in this part of the northeast.

Monarchs have four life stages; egg, larva (caterpillar), pupa, and adult (butterfly). The caterpillars feed only on milkweed leaves and seed pods. And, for this reason, adult Monarch females lay their eggs only on milkweed. In fact, the search for milkweed is the sole reason for monarch migration; perhaps the most remarkable migration in nature.

As the summer season comes to an end, shorter days, cooler temperatures, and declining milkweed quality signal biological changes that delay sexual maturity in monarch butterflies. The very last seasonal generation of caterpillars to emerge from chrysalises as butterflies here and across much of the northern United States and southern Canada will feast on late-season flower nectar before setting out on an epic 2,000-plus-mile migration south, to overwintering sites in the oyamel fir forests of the Sierra Madre Mountains, in central Mexico. It can take up to two months to complete the journey. (Gardeners take note. Late-summer-blooming plants are crucial for providing the energy resources monarch butterflies and other migratory pollinators, as well as native bees that will be hibernating here over the winter, require.)

monarch caterpillar by Richard GastThe entire eastern population of monarchs will have arrived in Mexico by late November; so many of them that the combined flapping of their wings creates a clear and constant sound. There they’ll overwinter in hibernation colonies, spending several months in diapause, a hormonally controlled state during which physiological activity is diminished and growth or development is suspended. Tens of thousands may cluster together in a single tree, waiting for the coming of spring when warming temperatures and longer days will signal that it’s time to mate. Barring disease, predation, and winter storms, they’ll breed sometime in March and the females will begin laying the eggs of a new generation.

The monarchs currently embarking on the arduous journey south are the great-great-grandchildren (and, in some cases, the great-great-great-grandchildren) of the butterflies that braved the long trip to Mexico at this time last year. They are sometimes referred to as the ‘Methuselah generation’ because they will live for seven or eight months, unlike the successive migratory generations of monarchs that travel north, living as butterflies for only a few weeks, as they search for flower nectar, mates, and milkweed, upon which to lay their eggs.

In early spring, the progeny of the Methuselah-generation-monarchs will leave Mexico to complete the first leg of the journey north, arriving and breeding in the American southeast. The brood hatched there will continue the migration northward, breeding along the way. It will require at least three generations of monarchs, each one traveling further north, to complete the migration from Mexico to the northeastern states and the provinces of southeastern Canada. They’ll arrive at the northern extremes of their range in late spring and early summer, and the cycle will begin once again.

adult monarch by Richard GastCounting overwintering monarch butterflies is an inexact science at best. Technicians and scientist-scouts walk through the forest and, at each roost, map trees occupied by monarchs. According to World Wildlife Federation (WWF) Mexico, last winter (2018-2019), monarchs occupied just under 15 acres of oyamel fir forest in the mountains of central Mexico. While this may not sound like much, it’s the largest population seen overwintering since 2007, and an increase of 144% over 2017-2018. Monarch hibernation colonies are so densely populated (5,500 butterflies per square yard, more or less) that the number of monarchs represented by this figure is … well … you do the math.

Anurag Agrawal, the James A. Perkins Professor of Environmental Studies at the Department of Ecology and Evolutionary Biology at Cornell University’s College of Agriculture and Life Sciences, writes in an informal article posted on the Insects on Plants, Chemical Ecology, and Coevolution website of the University’s Phytophagy Lab:

‘The monarchs end up congregating in a tiny area, with the bulk of the butterflies concentrated among twelve mountain massifs (clusters of peaks) within three hundred square miles, an area smaller than New York City. In other words, most of the monarchs from eastern North America, from Maine to Saskatchewan, and south to Texas, probably covering two million square miles, funnel down and overwinter in a location 0.015 percent the area that they occupy in the summer! Unbelievable. This year’s estimate is well over double compared to last year. Great news for monarchs!”

In that same post, Professor Agrawal asserts that monarch butterflies ‘have been declining over the past three decades, and the annual announcement is a welcome addition to our understanding of the long-term dynamics of our beloved monarch.’

Jorge Rickards, managing director of WWF Mexico, attributes the population increase to, among other things, pollinator-friendly conservation initiatives along the international migratory path.

We can all play a role in conserving these remarkable Lepidopterans by including milkweed in our perennial gardens. Several species, including common milkweed (Asclepias syriaca), swamp milkweed (Asclepias incarnate), purple milkweed (Asclepias purpurascens), and butterfly weed (Asclepias tuberosa) are attractive, fragrant, and native to New York.

Photos, from above: a monarch pupates in the relative safety of a firewood pile; monarch caterpillar feeding on milkweed; and adult monarch butterfly.

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Richard Gast is a retired Extension Program Educator and has been contracted by Cornell Cooperative Extension Franklin County to continue his informative and thought provoking articles.




27 Responses

  1. Boman Bushor says:

    Seeing many more this year than recent years here in Indian River(Croghan) ,NY.
    We have been leaving 7 acres of milkweed and golden rod uncut for the last 5 years. Was hoping it was helping the butterflies.

  2. […] In this online article from the Adirondack Almanack (the way the spell it) is an article declaring the Monarch butterfly is thriving there. A Good Year For Monarch Butterflies […]

  3. Ritaclare Streb says:

    Lots more monarchs seen this August and early September on the shores of Lake Ontario near Rochester, NY as they flew down from Canada.

  4. Nice summary, and, yes, this has been a wonderful summer for monarchs in the northeast. But the weather has been excellent for population growth this year, and that won’t be true every year, so we remain concerned about a long term decline in monarch abundance (emphasis on “long term”). Actually, only the first summer generation (descendants of the overwintering generation) complete the migration; following generations spread out and fill in habitat but don’t show the same directional movement as migrators. It’s very nice that so many people are noticing monarchs this year.

  5. Kevin says:

    We’ve also noticed this. My wife has counted roughly 100 that have hatched from a 300 sq. ft. plot of milkweed in Upper Jay.

  6. ADKBfly says:

    Richard and other interested Bfly fans….ADKers can help Monarchs and other pollinators by urging State, County and Local road crews to not mow roadsides during peak pollinator season June – Oct. Thousands of Monarchs and other insects are annually killed and their habitat destroyed by senseless mowing. Our ADK roadsides serve as habitat and migratory pathways for Monarchs and other pollinators. Also, consider converting part of your mowed lawn to pollinator habitat. Go to ADKAction.org and click on pollinator project to learn what can be done in the ADKs.

    • Boreas says:

      ADKBfly,

      Are road crews given any choice? I always assumed mowing schedules were dictated by the state. Even if immediate roadsides must be mowed on a schedule, I would thing medians and areas further from the road could be more flexible with mow times and even planted with pollinator-friendly species.

      • ADKBfly says:

        ADK Action is working to raise awareness with DPW, DOT and local Road Supervisors on the mowing issue similar to what they have done with road salt reduction. It doesn’t hurt to have the public urging them to cut back on mowing. Take a look online to see what OH and CT and MA are doing to reduce mowing to promote pollinator habitat.

    • Kevin says:

      Thanks for this comment. We were just talking about the milkweed that used to grow along the roads up here when I was a child. We’ve been allowing milkweed to grow on back lawn as are my parents. Small steps, but steps none-the-less.

      • Boreas says:

        Kevin,

        It doesn’t take huge fields of milkweed, but it would certainly help. I probably had fewer than a dozen plants this year and virtually all had Monarch caterpillars on them sometime this summer!

    • Ginny Alfano says:

      I talked to my local road crew mower guy and begged him not to mow down all the Milkweed on our little country road. He said he has no choice. If he doesn’t do it the way his boss sees fit, he’ll likely be out of a job. Sure enough, he mowed down everything and the boss drove by later to check on his work. All the Milkweed I had checked the day before were filled with Monarch Caterpillars. After that, they were totally decimated. Such a sad thing. The mower man said they have to mow so that people will see the deer better. It’s all a bunch of hogwash. They were very late cutting this year due to a mower problem. There were actually fewer car/deer accidents then in previous years. It all falls on deaf ears.

      • ADKBfly says:

        Hogwash is right. According to studies done on roadsides, deer are actually attracted to fresh growth in newly mowed areas. The study was done in OH before they instituted their program and is mentioned several times on the OH DOT website. ADK Action hopes to re-educate and create a new mowing mindset with these crews and their supervisors. Until then, the mowing crews need to change their warning signs from “Mowing Ahead” to “Killing Ahead”!

  7. I applaud what ADKAction is doing. When anyone talks with DOT folks, point out that mowing up to July 4th is fine, and mowing after the middle of September is fine. That’s enough mowing to enhance visibility for safety. But don’t mow July 4 to Sep 10; that’s monarch time.

  8. TonyF says:

    Yep I agree a lot of Monarch’s this year plus Yellow Tiger Swallow Tails and Black Swallow Tails as well. Very heartening to see.

  9. Kathleen Verdone says:

    On what do the monarchs lay their eggs in the spring in Mexico?

    • ADKBfly says:

      Kathleen Monarchs leave Mexico in March and lay on milkweed in Texas and other southern states, then they die. That generation takes about a month to grow and travels further north repeating the process. This past year I saw my first few Monarchs laying eggs in Minerva on June 8. The next wave came just before Fourth of July.

  10. Wanda konold says:

    I live on a farm in Pratt, Kansas. Will you please tell what common milkweed looks like?

    • Boreas says:

      Wanda,

      If you look at the caterpillar above, it is crawling on a milkweed seed pod. Not much else looks like those seed pods – 3-4 inches long. When the seeds ripen, the wind carries them off on fluffy down. The plant stands about 3-5 feet high and has long oval leaves. If you break a leaf in two a sticky, milky, sap emerges. The sap is noxious and not much will eat milkweed other than Monarch caterpillars. The caterpillars then take on this noxious character and not much will eat them!

  11. Where can I get milkweed seeds so I can plant them

    • Suzanne says:

      If you don’t find any milkweed pods locally, there are numerous sites you can google. One of them is

      http://www.birdsandblooms.com/blog/attracting-butterflies-free-milkweed-program

      but there are a number of other sources, many offering free seeds.

      It is great that so many people are ready and willing to help the Monarchs. Milkweed is actually a beautiful flower with a lovely scent.

      Thank you for your interest.

      • Boreas says:

        Suzanne,

        I will add that milkweed seed tends to germinate and grow very easily here! It just needs natural sun, soil, and water. But it doesn’t do as well in heavy shade. So if anyone has a shady plot, they may want to focus more on native, shade-loving, nectar-producing plants and scatter milkweed and/or wildflower seeds on any sunny neglected fields or disturbed landscapes they see nearby.

        However, until roadway management changes, it makes sense to avoid planting near roadways and other areas that are mowed frequently. Not only does early mowing defeat the purpose of planting milkweed and other wildflowers, it also destroys eggs and caterpillars, so it is best NOT to attract Monarchs to milkweed that will be mowed before hard frosts. It is counterproductive and essentially harmful to attract Monarchs to areas that will negate their breeding attempts by mowing. Neglected areas are probably best.

  12. Karen says:

    This is wonderful news. I wonder how they are doing here in Florida. I have them in my backyard but I thought there were less than last year.

    • Boreas says:

      Karen,

      I am kinda new to all of this, but the butterflies you see there are likely different than the ones we have here, unless you are only talking about the fall migration of the “Methusela” generation that is just occurring now. You may not have seen the peak of the southward migration yet this year. Plus, depending on where you live in FL makes a difference. The panhandle (St. Marks, etc.) is very important on the southward migration, whereas southern FL may be more important on the northward migration. Up here in the north country, we pretty much only see later generations earlier in the summer and the Methusela generation that will migrate and overwinter to Mexico.

      Milkweed is only part of the equation. The Methusela (Mexico-bound) generation is typically only interested in nectar to get them to Mexico. And when Monarchs are northbound in spring, they need both nectar and milkweed on which to lay their eggs. So anyone interested in helping Monarchs (and other pollinators!) should focus on native wildflowers, shrubs, and trees that provide nectar, of which milkweed is included. Even a modest 10′ X 10′ plot will be found and used by many pollinators. Every little bit helps! I have essentially stopped feeding birds through the summer because I get more enjoyment from tending and observing my modest wildflower gardens. Then I leave the seed heads standing for the birds in winter.

  13. Boreas says:

    Another interesting project to get involved in is the Buffer in a Bag project. Pollinator plants are included in these free bundles, and you can certainly add your own! The project is designed to help with erosion and water quality, but offers more than that. Check it out:

    https://www.dec.ny.gov/animals/115903.html

  14. Karen says:

    Thank you so much for all the info. I have a friend that is an expert on Native Florida plants. I have many in my yard. I also have several milkweed plants. She has informed me of her Dad who has been very active in helping the monarchs. He was very saddened this year by the lack of monarchs. I am not in the panhandle so I am not sure as to what kind they are.i will continue to research anything else I might do. Thanks again.

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