The Monarch Monitoring Project is a long-term study on monarch migration through Cape May, NJ. It is a part of the New Jersey Audubon Research Department, and closely affiliated with the Cape May Bird Observatory.

Sunday, November 8, 2020

November Monarchs

    Our field season runs from September 1 to October 31, and in some years we see very few monarchs after about October 20.  Big numbers of migrating monarchs arrive to the winter colony sites right around the beginning of November.  Since those colonies are 2000 miles away from Cape May, it makes sense that most monarchs should have passed through this area weeks earlier.  Early last week we saw a few days with cold, windy, and rainy weather, with reports of freezing temperatures and snow from northern New Jersey right up through all of New England.  Monarchs don't survive prolonged freezes, so we figured the migration was over.  For the last several years we have continued to conduct our census into November as a test.  We decided to do that again this year, but when there were no monarchs to be seen during the cold weather -- for a couple of days the census counts were all zero -- we figured our season was truly finished.

Monarch on lantana in Cape May Point, 11/6/20

    Then the weather changed, and suddenly we came into a spell of warm, sunny days.  And monarchs were back!  At first it was just a few, but numbers quickly grew.  It's nothing like the big numbers of early October, but it's still a surprise.  Our seasonal naturalists finished their work at the end of October, but we still have volunteers in town, and collectively we have tagged more than 200 monarchs over the last three days.

Monarch tagged at Cape May Point 11/8/20

    Unfortunately there's not a lot of nectar available for these late monarchs.  We're seeing virtually all of them in the few gardens that still have flowers in bloom -- Mexican sunflower, zinnia, lantata, and Vitex are still blooming in several gardens.  There's also a bit of the seaside goldenrod in bloom out on the upper beach.  But most places have no flowers left.  Many of the monarchs being tagged have little or no fat reserves, and fat provides the fuel for migration.  Will they find enough food to tank up for the next part of their journeys?  Will they find enough nectar as they go south from here to sustain them on their long travels?  Can they avoid freezing temperatures and make it all the way to Mexico?  We really don't know, and we assume that the odds are against the November monarchs, but we continue to actively tag, in hopes that some will be found further south and will provide hints, at least, to the answers to these questions.  We will be astounded (and delighted) if one of these November monarchs makes it to Mexico and the tag is seen by one of the observers there.

    We're also curious about where these November monarchs have come from.  Some that we are seeing are worn or even tattered, suggesting they've been around since before the early November storms, and they might not be fit enough to even try to migrate away from Cape May.  We are also seeing some that are pristine, looking very fresh.  We know that there are late caterpillars each year, and we suspect that as long as the weather permits, there will be newly emerged monarchs entering the population.  We know that they can't have come from terribly far north of here, for the freezes of early November in much of the northeast would have been fatal to any remaining monarchs, whether they were still caterpillars or if they had metamorphosed into the chrysalis or adult stages.  So it's our guess that our November monarchs began their lives in southern New Jersey or southeastern Pennsylvania.

    As long as the monarchs are still here, we will continue to conduct our censuses and we will keep tagging some of the monarchs that are in Cape May Point.  When we are tagging, we often attract curious onlookers, which gives us the chance for an impromptu lesson into monarch biology and conservation.  If you're in Cape May Point while our warm November weather continues, and if you see one of us out there with a butterfly net, don't hesitate to ask about our work, we're always eager to talk about monarchs.

Project Director Mark Garland gives an impromptu lesson about monarchs, 11/8/20

    A reminder: if you see a tagged monarch, make an effort to read the 4-letter, 3-number code on the tag -- the easiest way to do this is often to take a digital photo and then enlarge it on a computer until you can read the code.  Then go online to the website printed on the tag, mwtag.org, and add the requested data.  Watch the monarchwatch.org website in the coming months, for once all the data is assembled they'll report on all tagged monarchs that are subsequently found and reported.

Releasing a newly tagged monarch, 11/8/20

    We have started to compile the season's tagging data, but our annual summary will have to wait until we are truly finished with tagging for the year.  Rain is expected to come later this week, but it's predicted to stay relatively warm, so perhaps we'll keep seeing (and tagging) monarchs for another week or more. When we finally finish, we'll report back on the total number tagged by our team in 2020.





Thursday, November 5, 2020

Results of 2020 Census

Monarch nectaring on seaside goldenrod, Cape May Point

    Perhaps the most important parts of the Cape May Monarch Monitoring Project is the census that we conduct.  Our census is modification of a technique known as a "Pollard Transect," whereby a specified route is traveled on a regular basis and butterflies counted by the observer while traveling.  Our census is conducted daily from September 1 to October 31, and consists of a slow drive along a 5-mile route that leads from the west end of New England Road to Alexander Avenue in Cape May Point.  One observer drives at roughly 20 miles per hour and counts all of the monarchs observed along the route.  The census is conduct three times a day from September 1 to October 15, and then twice a day from October 16 to 31.  The number of monarchs seen along the route and the time of travel are recorded and then calculated to monarchs observed per hour.  These data are used to compare one year to another.  This census has been faithfully conducted every year since 1992, giving us 29 years of data.  Our data are summarized on a weekly and annual basis in this chart: 


    So how did 2020 compare to other years?  It was a good year of migration, with the 13th highest yearly average of monarchs observed per hour, 62.4, slightly above the median.  Putting it another way, 12 years have had a higher average but 16 have had lower.  There are many variables that affect the census numbers from year to year, but two seem to be most significant.  One is rather obvious: when the monarch population is high, we can expect to see more monarchs in Cape May.  The other significant variable is weather, with wind direction being the most significant.  A westerly component to the winds is likely to cause many monarchs to drift eastward, and if they end up on the east side of Delaware Bay, their preference to stay over land as long as possible will funnel them into Cape May.  Conversely, when the wind is blowing from the east, many monarchs coming from the north are likely to end up on the west side of Delaware Bay, bypassing Cape May altogether.  The same situation has been observed and is well documented with migratory birds, which are seen in the greatest numbers during the southbound migration when winds are from the west or northwest.  We saw favorable winds more frequently this fall than in many recent years.

Small roost of monarchs at Cape May Pt. State Park, Oct. 5, 2020

    Large average monarchs/hour totals for weeks 6 and 7 correspond to a 2-week period during the first half of October when monarchs were plentiful around Cape May.  It's quite unusual for Cape May to have consistently high numbers for two solid weeks, usually our peak numbers occur for just a few days at a time, though often we will see several peaks during the two-month migratory period.  Even though travel is severely limited this year due to the COVID-19 pandemic, and our education program was severely curtailed as we insisted on compliance with all pandemic precautions, we were able to help many local residents see and appreciate monarch migration during this period, and many more enjoyed the abundance vicariously through our social media posts.

Monarchs roosting in ivy at Cape May Point, October 11, 2020

    When you look at our 29 years of census data, it's noteworthy that while the numbers have some dramatic fluctuations (our highest yearly total is more than 40 times higher than our lowest year), the overall trend seems generally stable.  Some biologists have looked at our data and argued that it indicates that monarch populations are in good shape.  We are very reluctant to jump to that conclusion. Monarchs funneled through Cape May are a very small percentage of the numbers found all across the continent.  Censuses at the wintering areas in Mexico show dramatic declines in monarch numbers.  If monarchs in Cape May are doing okay for some reason, it certainly doesn't imply that monarchs everywhere are equally well.










Sunday, November 1, 2020

End of Field Season

The 2020 Field Season for the Monarch Monitoring Project wrapped up on Saturday, October 31 -- our field season runs from Sept. 1 to Oct. 31 each year.  We have started to compile the data and will report back to our followers in a few days, but we'll take a few minutes now to reflect on the season.  The COVID-19 pandemic has impacted virtually everything in all of our lives for most of the year, and that was true for our project as well.  Well into the summer it wasn't clear if we could run the project at all, or if we could hire seasonal naturalists.  Fortunately we found ways to take all of the appropriate precautions and continue to gather data and to hire two naturalists for our two-month season.  Thanks to the generosity of James & Teresa Knipper, who made an apartment available to us, we were able to hire one naturalist from out of the region.  And in the second bit of good fortune, we found a great candidate for the second position living right here in Cape May County.  We introduced them both to our readers before the season began, and now we want to thank them for a job well done.

Jack McDonough

Jack McDonough is a remarkable young naturalist who seems to be genuinely in love with every aspect of natural history here in his home county.  He grew up exploring the Belleplain State Forest of northern Cape May County, and while he is still a teenager, he has an astounding knowledge of our area's plants and animals.  He brought that enthusiasm for natural history to work every day, and while we had many fewer opportunities than most years to engage in educational outreach, Jack still managed to educate and excite the people he would meet while working around Cape May Point.  He's also a very skilled photographer, and he is assembling a set of photos for the use of those involved with the project in future years.  Watch for an upcoming book on the natural history and ecology of Cape May County that he's working on.

Kat Culbertson

Katherine "Kat" Culbertson wouldn't have been available to work with our project had 2020 been a normal year.  She was working as a Peace Corps volunteer in Madagascar when the COVID-19 pandemic forced the Peace Corps to bring everyone back home -- she had been scheduled to keep working over there until 2021.  With plans to begin graduate school in the fall of 2021, she was suddenly left with a gap in her plans, and to our good fortune she found our project and accepted the job on short notice.  Her strong academic background from Harvard University put her in a great position to work with some of the data that we have gathered over the project's 30 year history -- and it looks like a scientific publication will result from her work.  Kat, like Jack, was a great ambassador for monarchs in our educational programs and the many informal contacts that happen when you walk around Cape May Point with a butterfly net.

Our project would not be able to continue without the hard work of our seasonal naturalists.  We offer a huge amount of thanks (and a few very modest paychecks) to both Jack and Kat for the great work that they both accomplished.  We also benefit from the work of many volunteers who help with our tagging, and most importantly, from donors who make contributions throughout the year, whether "adopting" one of our tagged monarchs, contributing to our "Monarchists" team in the annual World Series of Birding fundraiser, or making other donations.  We run a vigorous program on a very small budget -- the salaries of our seasonal naturalists are the biggest expense -- and this year we missed out on the funds that are generated annually as part of our tagging demos at Cape May Point State Park.  Very big thanks to all of you who have made contributions in the past, and if you're in a position to make a contribution this year, contact us at monarchs@njaudubon.org for details on how you can help.

Monarch feeding on Mexican sunflower in Cape May Point

As for the monarchs, we continued to see a few around Cape May Point right through October 31, but with freezing temperatures throughout New England and south into central New Jersey on October 30, we can't expect more to be migrating from our north.  It didn't freeze here, however, and a few late migrants might still be around, but the 2020 monarch season is essentially over.  That's how it should be, as the beginning of November typically heralds the arrival of huge numbers into the Monarch sanctuaries of central Mexico, and indeed people have been seeing thousands upon thousands flying into those amazing Mexican mountain forests.  As we've done for the last 3 years we'll continue our census for one extra week into November, but our job is now mostly wrapping up the season's data, preparing our annual report, and getting all of our project equipment organized and stowed away, awaiting the beginning of the 2021 field season.


 



Thursday, October 22, 2020

Bonus Programs

The last of our originally scheduled educational programs occurred on October 17.  With the continuation of mild weather, and the presence of good numbers of monarchs around Cape May, we are pleased to offer to extra "bonus" programs this fall.  Preregistration is required, like all of our programs this fall.  To register visit the New Jersey Audubon website.


Monarch Biology: Friday, October 23, 1:30 to 2:30 pm

Join CMBO Monarch Monitoring Project naturalists for this special program about the Monarch migration through Cape May!  Join CMBO Monarch Monitoring Project naturalists for a stroll through a milkweed-filled meadow to learn about Monarch Butterfly biology and migration. We’ll hope to see monarchs and other butterflies, and we’ll wrap up by tagging one or more monarchs and send them on their way to Mexico. Family-friendly.  Meet at The Nature Conservancy's Garrett Family Preserve.

COST: $6 members, $10 nonmembers.


Invasive Mantids: Saturday, October 24, 1:30 to 3:00 pm

Join Naturalist Jack McDonough to learn about the three species of Mantids in Cape May and how they’re impacting the Monarchs butterflies.  Every summer and fall, hundreds of Monarch Butterflies are hunted and eaten by invasive species of mantis. Monarchs, who have already been so heavily in decline in recent years due to anthropogenic activity, suffer even further from invasive mantis. Our goal here at the Cape May Monarch Monitoring Project is to help remove the invasive mantis as best we can from our area. Would you like to help take action? Would you like to be responsible for saving hundreds of lives of the incredible Monarch Butterfly and help restore their population? Then come join us on Saturday October 24th and learn how you can help.

There are three species of mantid found in Cape May, one is native but two are introduced, often outcompeting the native species and causing other environmental damage. Learn to identify all three species, both as adults and by their egg masses (“Ootheca”), then take a walk along the trails at Cape May Point State Park to remove egg masses of the invasive species.

COST: FREE, but preregistration is required.

A fallen Monarch… a beautiful female taken by the hungry claws of a mantis.
They eat the butterflies head and body after stripping off their wings, as seen here,
where the wings are left to blow away in the wind.

NEW JERSEY AUDUBON’S PROGRAM GUIDELINES:

New Jersey Audubon field trips and programs adhere to CDC guidelines; leaders have the right to ask a participant to leave the program if someone is not adhering to these guidelines for the health and safety of all. Leaders and participants must wear face coverings throughout the program and maintain social distancing (at least 6’ of separation). Leaders may remove their face covering in order to be heard by the group while maintaining social distance. Please do not come to a program if you are sick or have a sick family member. There will be no sharing of equipment including binoculars or spotting scopes.

***If you have spent time in a state that appears on New Jersey’s Travel Advisories, we request that you do not attend the program and will provide a full refund.***

WHAT TO BRING: It is recommended to bring your own clippers, if you want to help remove the egg masses from trees. Bring binoculars if you have them.

TRANSPORTATION: We may walk up to 1.5 miles, over generally level, sometimes muddy or sandy terrain. Some trips involve walks over jetties.

CANCELLATION: CMBO programs require a minimum number of registrants to run, five days in advance of the start of the tour, but are seldom cancelled. If we do cancel, due to lack of participation, severe weather, or unforeseen circumstances, we notify all participants in advance and all are eligible for a full credit or refund. Participants may cancel without penalty if greater than 30 days in advance. Cancellations 10 to 30 days in advance may be subject to a 25% service charge. No refunds or credits for cancellations less than ten days in advance unless due to health emergencies

Thursday, October 1, 2020

How to Raise Monarch Caterpillars

 Director's Note: Our two seasonal naturalists for 2020, Katherine Culbertson and Jack McDonough, are preparing a series of blog posts designed to educate readers about many aspects of monarch biology and related topics.  Here's the fourth of this series, written by Katherine Culbertson, and titled: 

How to Raise Monarch Caterpillars

In our previous educational blog post, we talked about the monarch’s life cycle; if you want to watch this fascinating process up close, it’s easy to raise your very own monarchs. In fact, many elementary school science classrooms hatch out monarch and other butterflies to teach kids about metamorphosis, but you’re never too old to witness this magical process. Below is all the information you need to get started!

  • A few key things to remember before bringing monarchs home:
  • Monarch caterpillars ONLY eat milkweed, and must always have fresh food
  • Monarchs must be in a naturally lit area (but not in direct sunlight) for them to properly develop; a shaded porch is ideal, but an indoor room with natural lighting can work in a pinch
  • It will take about 4 weeks for your monarch eggs to turn into an adult butterfly
  • Be sure to release your monarchs close to where you found them! (i.e. Please do not bring them to Cape May to release if you didn’t find them here.)
  • It is inadvisable to raise large numbers of monarchs; just a few give you chances to observe the whole process of growth and metamorphosis.

You will need:

  • Bug box, aquarium tank, or similar container with good airflow
  • Milkweed cuttings – be sure to collect the same variety you found your caterpillar(s) on
  • Either: 
  • (1) A small bottle or similar container filled with water (to put milkweed in) AND Plastic wrap or foil (to cover water so that caterpillars don’t fall in!) 
  • OR
  • (2) Wet paper towels

Before you collect your monarch caterpillars, be sure you have a secure place to keep them with good airflow. Caterpillars are escape artists, so there cannot be any gaps small enough for them to fit through. A bug box or aquarium with a mesh lid makes a good home for caterpillars, as does a mesh butterfly cage. Be sure to place your caterpillars’ new home in a place with natural lighting, but not in direct sunlight.

The best place to find your monarch eggs or caterpillars is in your garden, or another milkweed patch close to your home. There are three species of milkweed that you can find monarch eggs on near Cape May – swamp milkweed, common milkweed, or butterfly weed. (If you live outside of Cape May, check what milkweed varieties grow in your area!) Caterpillars or eggs can be found on milkweed plants from May to October. Check the small tender leaves at the top of plants especially well – female monarchs often prefer laying eggs on these leaves. Eggs can be tricky to find, as they are only about the size of the head of a pin! They are off-white in color, and are always laid individually; if you spot a cluster of eggs, they are definitely not monarch eggs. The best way to spot tiny caterpillars is to look for small holes in milkweed leaves, where they have just begun to eat.

If you find a leaf with an egg on it that is close to the top of a milkweed plant, if is best to snap off the entire top of the plant and stick it in water (see below), as this will keep the leaves fresh until the egg hatches. If this isn’t possible, break off the leaf and wrap the end in a wet paper towel, making sure to moisten it twice a day and provide fresh leaves as soon as the caterpillar hatches (which may take up to 4 days). 

For the next two weeks, as your caterpillar(s) grow, it is important that they always have access to fresh milkweed. There are two ways you can do this:

(1) Cut off the top of a milkweed plant and place it in a bottle or similar container filled with water (the same way you would place a bouquet of flowers in a vase). Be sure to cover the gap between the milkweed stem and the edge of the container with plastic wrap or foil so that the caterpillar(s) don’t fall in the water and drown! Caterpillars don’t need to drink water directly, as they get all the water they need through eating milkweed leaves. Replace the milkweed cuttings if they start to die, dry out, or if your caterpillar has eaten nearly all the leaves. 

(2) Break off a few milkweed leaves, and wrap the cut ends in a wet paper towel. Be sure to keep the paper towel wet, and to provide your growing caterpillars with fresh leaves every day!

When your caterpillar is ready to form its chrysalis, it will start wandering around, looking for a good, secure spot. It’s especially important to be sure it can’t get out of the container you’ve placed it in now – if it does, you may never find it again! Before it forms its chrysalis, the caterpillar will hang upside-down in a J shape. Don’t worry, there’s nothing wrong with it – it’s just getting ready to shed its skin for the last time and transform into a chrysalis. It’s very important to not disturb it while it is in this stage, so if it chose to pupate on the lid of your caterpillar home, wait to open it until it has shed its skin and the chrysalis has hardened before carefully removing the lid.



After about 10-14 days, you’ll notice the chrysalis starting to darken; it will turn a purple-black color, and you’ll be able to see the orange wings of the developing butterfly! At this point, be very careful not to disturb the chrysalis. Soon, the butterfly will emerge, its wings wet and crumpled. The new butterfly must hang upside down for a couple of hours to allow its wings to dry, and if it is disturbed during this time, it might injure itself and never be able to fly properly.

Once the butterfly has completely dried its wings and starts to flap them, it is ready to go! Release it back into the wild near where you found it, and if it hatches out in Sept/Oct, perhaps it’ll make it all the way to Mexico!

Note: Remember, not all caterpillars will survive until adulthood. Some may become sick, some are parasitized by wasps (this is why it’s better to collect small caterpillars than large ones) and some aren’t able to properly form or hatch out of their chrysalis. As long as you’ve provided your caterpillar(s) with good food, kept them in a naturally lit place, and left them alone while they’re pupating, you’ve done the best you can, and if some of them don’t make it, it’s not your fault! It’s just part of life. Remember, butterflies have different life strategies than us - each female butterfly will lay 100-300 eggs, and only a few of those will actually survive to adulthood. 


Sunday, September 27, 2020

Season Update, September 27, 2020

It's been a while since our last post, and we apologize for that, but we're starting to get busy with monarchs in Cape May Point.  The weather changed abruptly on September 18, with cooler temperatures and winds blowing from the north.  North winds trigger migration, but most monarchs come into Cape May when there's also a westerly component, and for 4 days we had winds from the northeast.  We saw some influx of monarchs into Cape May, certainly more than we had seen earlier in the season, but the numbers really picked up over the last 3 days.  Gentle northeast winds today triggered an exodus, as many headed out across the Bay towards Delaware, but there's still no shortage of monarchs at Cape May Point. South winds are predicted for Monday and Tuesday, and while that's not likely to bring many more monarchs into Cape May, the ones that are here aren't likely to leave.

Monarchs at Cape May Point, 9/27/20

That should all change Wednesday, if the forecast holds, when the next cold front is predicted to arrive bringing northwest winds and, with luck, a big influx of migrating birds and monarchs.  Another front is predicted to arrive on Friday, meaning we could be in for several excellent days for viewing monarchs throughout southern New Jersey.  Most of our work is focused on Cape May Point, and we suggest that monarch fans visit the public gardens at Pavilion Circle, the south end of Lake Lily, Triangle Park, and Cape May Point State Park -- all can be very good spots for viewing monarchs.  

Monarchs at the south end of Lake Lily, Cape May Point

The next week will bring the beginning of the bloom period for seaside goldenrod, a great nectar source that is widespread in the dunes.  You can observe from the beach or one of the dune crossover trails, but never walk into the dunes away from the paths -- footsteps can quickly turn into erosion on these sandy structures, and the dunes are crucial for protecting coastal areas from storm tides and floods.

Monarch on seaside goldenrod, Cape May Point dunes, 2019

There are many other places where monarchs concentrate in southern New Jersey.  The south end of the barrier islands along the Atlantic coast are often excellent, places like the Two Mile Beach Unit of the Cape May National Wildlife Refuge and Stone Harbor Point.  There are some great spots along the Delaware Bay shore as well, with East Point, at the mouth of the Maurice River in Cumberland County, a particularly good location.  Any meadow filled with fall-blooming flowers can be good, such as the meadow filled with tall goldenrod at the Garrett Family Preserve, where our team is conducting monarch programs on Friday and Saturday afternoons this fall.  Find information about registering for our programs here: https://njaudubon.org/event/monarch-biology-5/.  Pay careful attention to the directions if you do sign up, some folks have had trouble finding this hidden gem of a nature reserve, which is owned and operated by The Nature Conservancy. 

Meadow filled with tall goldenrod at the Garrett Family Preserve

Our team has been tagging lots of monarchs, so it's time for our annual reminders about tagging monarchs.  If you see a monarch with a tag, try to read the code that's the final line on the tag, consisting of 4 letters and 3 numbers.  On the monarch shown below, that code is ACBA 170.  Often a digital photo can be enlarged on the computer and the tag code can be read.  Visit the web address shown on the tag, mwtag.org, and fill out the form with the date and location of your find, and you'll be making a big contribution to our understanding of monarch migration.

Monarch ACBA 170, tagged at Cape May Point

We know that there are other monarch enthusiasts who tag -- anyone who is interested can purchase tags from Monarch Watch, and there's no special license required.  If you're a tagger and you're not part of our project, we'd suggest visiting one of the other sites listed above, as we have Cape May Point well covered, but if you do tag here, we ask that you share your tagging data so we can include your tagging numbers with our long-term data set.  Many thanks!






Wednesday, September 16, 2020

Monarch Life Cycle

 Director's Note: Our two seasonal naturalists for 2020, Katherine Culbertson and Jack McDonough, are preparing a series of blog posts designed to educate readers about many aspects of monarch biology and related topics.  Here's the third of this series, written by Katherine Culbertson, with photos by Katherine (except chrysalis and Mexico photos by Mark Garland), and titled: 

Monarch Life Cycle

We’re all familiar with adult monarchs – the beautiful black-and-orange butterflies flitting around Cape May right now, sipping nectar out of flowers. But this is only part of their amazing life cycle – and a small fraction of the life of most non-migratory generations. 

Adult female monarch butterfly

Monarch egg

Monarchs start life as a tiny egg laid on a milkweed leaf. Every female monarch will lay around 100-300 eggs in her lifetime, each on its own individual leaf. Milkweeds, plants of the genus Asclepias, are the host plants for monarchs; their caterpillars won’t eat anything else. There are 73 species of milkweeds native to the U.S., of which about 30 are known to be used by monarchs. These plants can vary widely in appearance, ranging from the large broad leaves of the common milkweed to the narrower, pointy leaves of butterfly weed and swamp milkweed, and to the vine-like climbing milkweed.

Newly hatched monarch caterpillar

After about 4-6 days monarch eggs hatch into tiny caterpillars. A newly hatched caterpillar doesn’t have its bright yellow, black, and white banded pattern yet; it also isn’t poisonous yet, as it hasn’t eaten enough milkweed. As the caterpillar grows, its striking colors become more defined. This coloration serves as a warning to birds and other would-be predators that monarchs do not make a good snack – they sequester a toxin from the milkweed they feed on that is toxic to any vertebrates that might try to eat them. A caterpillar’s only job is to eat; and eat, eat, eat, they do! From the time they hatch to when they form their chrysalis – a mere 10-14 days – a monarch caterpillar will increase in size more than a thousand-fold. For comparison, that’s like if a human baby, born at 8lbs, grew to be the size of an Asian Elephant in two weeks! As they grow, monarchs must shed their exoskeleton; that is, they must discard the tough chitinous material that covers their bodies to allow them to continue growing. This process is called molting. Each time a monarch molts, it transitions to a new stage called an instar. Monarch caterpillars molt 5 times during their lives, and thus have 5 instars.

Fifth instar monarch caterpillar

When monarchs have reached their 5th instar, after about two weeks of eating and growing, they are ready to pupate – to form a chrysalis, within which they will go through the process of metamorphosis, transforming into an adult butterfly. Once the 5th instar caterpillars become ready to pupate, they get the urge to wander until they find a suitable, protected place to form their chrysalis. Once they have selected a site, they attach themselves to that spot with silk, and hang upside down in a “J” shape. Soon, they molt a final time, and their appearance has completely changed – gone is the black, white, and yellow striped caterpillar, and in its place, an emerald green chrysalis hangs, decorated with gold “jewels”. The chrysalis may look dormant, but much is happening inside. The various parts of the adult butterfly – legs, wings, and other things – have already started growing within the large, fleshy body of the caterpillar, but now they continue to develop and rearrange within the chrysalis to assemble the adult butterfly. 

Monarch chrysalis 

After about two weeks, the chrysalis will start to change color, shifting from emerald green to a dark, purple-black tone; the bright orange of the butterfly’s wings starts to show through, as well. The butterfly is almost ready to emerge! Soon, the bottom of the chrysalis splits open, and out crawls the fully formed butterfly. At first, the butterfly’s wings are wet and crumpled, and the newly emerged butterfly must wait for them to expand and dry out before taking its first flight. Its proboscis – the straw-like mouth that allows it to suck nectar out of flowers – also isn’t properly formed yet when it hatches out. The two sides of the proboscis must “zip” together after it hatches out. Once the butterfly’s wings have dried, you can tell whether they are male or female – the males have an elongated black patch on both of their rear wings, which produces chemicals used in courtship by many species of butterflies. Females don’t have these patches, and also tend to be slightly darker and smaller than males, with thicker black wing veins.

Adult male monarch

Mating monarchs

Most monarch adults only live about 2-5 weeks, and don’t migrate long distances. Every summer, 3 or 4 generations of these non-migratory monarchs hatch out, migrating relatively short distances as the weather warms and their summer range expands. They mate and lay eggs along the way, parenting the next generation of monarchs. The final generation of the year, however, has a completely different life in store! As the fall approaches, something – no one is sure exactly what – causes this final generation to delay their reproduction and start migrating south. These are the butterflies that will fly hundreds, perhaps more than two thousand miles, and overwinter in Mexico. As they travel, the nectar they drink from flowers allows them to build up enough fat reserves to spend the winter dormant in Mexico. Unlike the previous generations, they will live 6 to 9 months, and in the spring, they will reawaken, mate, and lay eggs as they start to venture north, beginning the first generation of summer monarchs for the next year.

Monarchs starting to head north from Mexico wintering grounds