The Marvelous and Mysterious Monarch

Visitor essay by Kip Hansen

The marvelous Monarch Butterfly is an icon of organic thriller.  Once I was born, circa 1950, monarchs had been identified to fly north into southern Texas each spring by the tens of millions.  Within the Fall, vacationers would go to Cape Might, New Jersey, timing their visits to look at the wonder and pageantry of the Monarch Migration south once more as they’re funneled down the southern New Jersey peninsula from New England and factors north, headed south to an unknown vacation spot, believed to be someplace in Mexico.

It wasn’t till 1975, lengthy after I had handed by college, that the placement of the monarch overwintering website within the central mountains of Mexico was found.  For 40 years, Dr. Fred Urquhart had looked for the monarch’s overwintering website…lastly discovering the placement within the fall of 1975.  Urquhart wrote of his discovery in Nationwide Geographic journal, which had funded his search, within the August 1976 problem.  He didn’t, nonetheless, reveal the precise location of the butterfly colonies at the moment, not even to different scientists.

As this picture in the beginning of this essay reveals monarch butterflies start to maneuver south each August (the orange arrows).


“Not like most different bugs in temperate climates, Monarch butterflies can not survive a protracted chilly winter. As an alternative, they spend the winter in roosting spots. Monarchs west of the Rocky Mountains journey to small groves of timber alongside the California coast. These east of the Rocky Mountains fly farther south to the forests excessive within the mountains of Mexico. The monarch’s migration is pushed by seasonal adjustments. Daylength and temperature adjustments affect the motion of the Monarch.

In all of the world, no butterflies migrate just like the Monarchs of North America. They journey a lot farther than all different tropical butterflies, as much as three thousand miles. They’re the one butterflies to make such a protracted, two manner migration yearly. Amazingly, they fly in plenty to the identical winter roosts, typically to the very same timber. Their migration is extra the kind we count on from birds or whales. Nevertheless, in contrast to birds and whales, people solely make the round-trip as soon as. It’s their kids’s grandchildren [or great-grandchildren and even great-great-grandchildren]  that return south the next fall.”  [ hyperlink ]

Migrating Monarch populations have been in bother because the flip of the century as measured by the realm occupied at their overwintering website in Mexico — and secondarily at their West Coast overwintering websites on the coast of California.


These two graphs finish in 2013 – 5 years in the past – and it appears to be like fairly grim.

So, are monarch butterflies endangered, as so many activist organizations and their press releases declare, threatened with extinction?  Have they been greater than decimated by pesticides?  Are they doomed by local weather change?

SPOILER ALERT:  Clicking this hyperlink offers you the reply! (opens in a brand new tab)

These of you not affected by the determined want for speedy gratification  can learn on . . . . . the story of the monarchs is fascinating.

Let’s give that general inhabitants statistic one other more-up-to-date look to  embrace this winter’s stats from Mexico:


This inhabitants (above) represents 99% of the North American migrating inhabitants.  As we will see on this graphic, the bottom level was within the winter of 2013-2014 — this winter, 2018-2019, reveals an virtually ten-fold improve from that point.  The Western Migration inhabitants (not proven), nonetheless,  is at an all-time low this winter, as dangerous as that sounds, the Western migrating inhabitants (west of the Rocky Mountains) solely contains 1% of the general inhabitants of migrating monarchs in the US.

What’s that in numbers?

“Researchers have estimated that there are roughly 21.1 million butterflies per hectare, though this quantity most definitely varies with the time of the winter because the colonies contract, broaden, and transfer. It additionally varies with the density and measurement of the timber within the colony. Primarily based on this estimate the biggest inhabitants of monarchs occurred in 1996-1997 when the colonies coated over 18 hectares and contained an estimated 380 million butterflies. So far the bottom inhabitants recorded was in 2013-2014 with zero.67 hectares and roughly 14 million monarchs.” [ hyperlink ]

Utilizing Lincoln Brower’s components for the present 2018-2019 winter offers us an estimated 127,655,000 monarchs hugging the oyamel firs in Mexico this 12 months.  Sure, that’s 127 million.

 One million of something is quite a bit — click on this hyperlink to see a picture (in a brand new tab) of one million dots, certainly one of which is purple.

College students of Inhabitants Dynamics ought to discover the graph above instructive. The inhabitants of migrating monarchs is just not a part of a predator-prey dynamic however fairly a carrying capability dynamic (through which the carrying capability of the setting is the limiting issue to inhabitants numbers).  The non-linearity of the inhabitants dynamic  is obvious within the numbers, with typical boom-and-bust habits,  on prime of what seems to be a gradual decline — which, when the data to observe right here is taken under consideration, seems to be pushed by a change in carrying capability of the monarch’s North American vary.

Are the Monarch’s Endangered by Local weather Change?  No.

Naturally, the claims of pending doom for the monarchs features a very giant Local weather Change issue.  Almost each article on monarchs consists of that they have to be threatened by local weather change, both within the current or definitely sooner or later.  Many of those claims use the RCP8.5 to say that monarchs will likely be compelled additional north in vary, in search of milkweed, rising the size of their migration.  One other angle is that tropical milkweeds, which develop 12 months round within the south of North America, will grow to be extra poisonous with rising temperatures harming the monarch caterpillar stage which feeds excusively on milkweed leaves and these imported, invasive tropical milkweeds have a better toxicity which was proven to extend when grown beneath increased temperatures.  Nevertheless, neither of those two hypotheses are effectively supported by proof, fairly they’re fears for the long run.

As soon as the monarchs migrate north to Texas and past, they breed and develop all through the whole northern vary, following the blooming of milkweed, a lot of which develop and bloom all summer season.  Monarchs that overwintered in Mexico breed in Texas as quickly as they discover milkweed vegetation on which to put their eggs.  These butterflies then die, however their off-spring maintain shifting north, breeding era after era of latest monarchs, every era staying put if milkweed and nectar-flowers can be found, or shifting north to observe the seasons.  Monarchs, in contrast to many chook species, would not have a particular vacation spot to which they head for breeding functions…they breed all alongside the way in which.  Some maintain shifting — some settle in the place they discover themselves,  so long as situations are favorable.  There isn’t any purpose to consider that they won’t proceed to take action,  adapting their migration [or even abandoning the migration as some non-migrating populations have] because the local weather adjustments

The opposite Local weather Change fear is that “the quantity and depth of storms will improve”.  That’s supposition and has not been discovered within the information thus far. However, as a result of butterflies are fragile, the Monarch Migration can and has been adversely affected by climate:

2002:   “Between 12-16 January 2002, a extreme winter storm hit the monarch sanctuary area deep in central Mexico. Mexico’s over-wintering websites harbor all of japanese North America’s migratory monarch breeding inventory. Dr. Lincoln Brower and colleagues launched mortality estimates. Primarily based on information collected from the 2 largest sanctuaries, over 75% of the inhabitants was killed by this single storm.”  [ The next overwintering season saw Monarch numbers only down by 20% — an astonishing recovery from a 75% mortality event! ]

2010 and 2016:  “Storms earlier this 12 months (2016) blew down greater than 100 acres of forests the place migrating monarch butterflies spend the winter in central Mexico, killing greater than 7% of the monarchs, in line with conservationists.”

“Rain, chilly and excessive winds from the storms brought on the lack of 133 acres (54 hectares) of pine and fir timber within the forests west of Mexico Metropolis, greater than 4 occasions the quantity misplaced to unlawful logging this 12 months. It was the largest storm-related loss because the winter of 2009-10, when unusually heavy rainstorms and mudslides brought on the destruction of 262 acres (106 hectares) of timber.”

“This 12 months’s storm additionally seems to have frozen or killed about 6.2m [million] butterflies, virtually 7.four% of the estimated 84m butterflies that wintered in Mexico, stated Alejandro Del Mazo, the legal professional common for environmental safety.”

2016 (recount):  “Roughly 30-38 % of the monarch butterflies (Danaus plexippus) within the Sierra Chincua and Cerro Pelón overwintering colonies died within the storm, says a workforce led by Lincoln Brower, Ph.D., analysis professor of biology at Candy Briar Faculty, way over the estimated 7 % mortality charge cited in preliminary media studies after the storm that struck between March 7 and March 11, 2016.”

Hurricanes coming ashore in Texas in late-September and October would have an effect on the migration because it heads for Mexico.  Just one hurricane since 1980 fills this area of interest:  “October 20–24, 2015 – Hurricane Patricia’s remnants deliver heavy rain to Texas. The utmost rainfall whole is reported to be 20.87 in (530 mm) in Corsicana. This rain causes the flooding and closure of Interstate 45 in that space.”  It doesn’t appear to have affected the migration in 2015-2016 as that 12 months’s overwintering inhabitants was really three occasions bigger than the previous 12 months.

However in the long run, we’ve got this cheering information:

“Even so, most monarch scientists don’t consider monarchs will grow to be extinct.”

“The migration received’t final eternally. The monarchs will,” stated migration professional Andy Davis, Assistant Analysis Scientist on the Odum Faculty of Ecology on the College of Georgia and editor of the journal, Animal Migration. “The monarchs will adapt identical to they’ve in each different inhabitants world wide,” he stated.”

Wait a minute!  What does he imply when he says “The migration received’t final eternally. The monarchs will.”?

The venerable Nationwide Geographic studies:

Are Monarch Butterflies Endangered?

“The quick reply is not any. Monarch butterflies are literally fairly widespread the world over, with populations occurring as distant as North Africa and New Zealand.”

“Nevertheless, the subspecies referred to as Danaus plexippus plexippus is the one one which performs the good North American migration—and these butterflies are more and more beneath risk.”

The Smithsonian Institute studies:

“Monarch Butterflies:  ORDER: Lepidoptera | FAMILY: Nymphalidae | GENUS: Danaus | SPECIES: plexippus

Standing: Widespread widespread butterfly, greatest referred to as migrant.”

Many areas within the southern United States assist year-round populations of Monarch Butterflies, significantly southern Florida.  There are some year-round native populations in southern California, the place there are additionally some western monarchs which migrate to Mexico as an alternative of the California coast.  “Within the Americas, the monarch ranges from southern Canada by northern South America. It has additionally been present in Bermuda, Prepare dinner Islands, Hawaii, Cuba, and different Caribbean islands, the Solomons, New Caledonia, New Zealand, Papua New Guinea, Australia, the Azores, the Canary Islands, Gibraltar, the Philippines, and North Africa. It seems within the UK in some years as an unintentional migrant.” [ hyperlink ]

It’s the Monarch Migration, as a phenomena, that’s probably endangered.  And it could be unhappy to see such a improbable, surprising, mysterious phenomena disappear.  Nobody is aware of how the super-generation of monarchs is aware of to fly south and manages to search out the identical little patch of firs in far off Mexico.


California Monarchs overwintering on eucalyptus. [photo credit – charles the moderator]

What  do consultants actually suppose is inflicting the decline in migrating monarchs?

Monarch populations are restricted by the carrying-capacity of their vary  — which means that the key issue limiting numbers is the provision of the required breeding plant (milkweed species) and sufficient meals sources — nectar crammed flowers.

That stated, there are many nectar crammed flowers within the North American setting however not so with milkweed.    Milkweed is a standard weed that loves disturbed soils — plowed fields, roadside ditches, hedgerows, freeway verges.  It was once a serious competitor within the corn belt’s tens of millions of acres of corn and soy beans.  What occurred to all that milkweed?

Public enemy #1:  Spherical-up.  A herbicide that simply works as designed — it kills vegetation that aren’t genetically engineered to face up to it.


Newly launched “round-up prepared” corn and soy beans now permit the between-the-rows milkweed to be killed with out damaging the supposed crop.  In 2018, 94% of soybeans, 91% of cotton and 90% of corn planted within the US was an herbicide-resistant pressure.  All of that acreage was once prime milkweed habitat, rising between rows and on the sides of farm fields.  Nearly all of that traditionally obtainable milkweed has been misplaced.

This represents a case the place an agricultural apply change led to by a technological advance in biology has had the supposed impact — fewer weeds competing with crops boosting crop yields — however which has been accompanied by an unintended impact — the lack of milkweeds subsequently suppressing populations of Monarchs.

This loss is seen not solely within the corn, cotton and soy fields, however on the roadsides and waste land the place weeds are being mowed or handled with herbicides.  In my space, the land alongside railroad tracks sports activities wild native milkweed, however simply because it begins to mature, it’s mowed down.  The identical is occurring throughout America – vegetation that we think about as weeds are being eradicated.

Monarchs want milkweed to breed, they lay eggs solely on milkweed and the younger caterpillars eat solely milkweed.  Extra particularly, they want native milkweeds, not the usually prettier non-native tropical milkweeds bought to gardeners.

Lack of native milkweed within the North American breeding grounds — Texas to the Nice Lakes — is the first issue that has restricted monarch populations and is believed to be the key issue resulting in their regular decline because the flip of the century.

There are many teams which are selling milkweed planting (bear in mind to insist on native milkweeds) and butterfly-friendly dwelling gardens that present prepared sources of nectar for the monarchs and different butterflies.    An web seek for butterfly-friendly gardens and milkweed sources will level you to the correct locations.  (Most of the hyperlinks on this essay go to monarch-specific websites that comprise info.)

The opposite limiting issue is lack of overwintering habitat in Mexico resulting from unlawful logging.  To appropriate this, the federal government there has created a Monarch Butterfly Biosphere Reserve.  There are ongoing studies of continuous unlawful logging within the oyamel fir forests of central Mexico, contained in the reserve.  There have been damaging storms because the flip of the century (detailed above) [and in all probability there have always been storms]  which have felled timber there and brought on mudslides.  However as we see within the inhabitants graphs above, monarch populations appear to have the ability to bounce again.

Be aware that there are some myths and superstitions concerning the oyamel — one is that monarchs return to the “identical tree” every year, which is utter nonsense.  It isn’t the identical butterfly that left which is returning however a great-great-grandchild.  However it could be true that the monarch swarms do are likely to kind on among the timber utilized in earlier years — no matter it’s that pulls them to a particular tree could effectively entice them once more — they might depart a scent marker on timber once they use them — analysis continues on this fascinating topic.

Take Residence Messages: 

  1. Monarch butterflies characterize a virtually distinctive phenomena of their North American migration habits — an exquisite factor to look at — and effectively value conserving.
  1. Our North American Migratory Monarchs face challenges in our trendy world — lack of obtainable milkweed being the first drawback.
  1. You possibly can assist. You possibly can plant native milkweeds (a lot of that are beautiful) and butterfly-friendly flowers in your yards and gardens.  You possibly can encourage native authorities to depart milkweed patches unmowed on public land.  You possibly can take part in Monarch Citizen Science packages all throughout the US:  Monarch Joint Enterprise,  US Forest Service,  the Monarch Larva Monitoring Challenge, Journey North’s monarch migration monitoring program, and several other alternatives for giant and small venture with Monarch Watch.   The Xerces Society itself has packages and hyperlinks to different monarch packages, together with sources of milkweed seeds.
  1. Monarchs should not threatened by local weather change — however could be adversely affected by climate phenomena. It’s past to manage the climate, however we will assist monarchs and add to their resilience by defending their overwintering websites (effectively underway) and act to extend obtainable milkweed of their breeding ranges.

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Writer’s Remark Coverage:

An attention-grabbing subject and one more instance of one thing good that’s not actually threatened by local weather change.  (That’s a protracted listing…)

Yearly within the summers I are likely to cease and search milkweed patches for monarch eggs and caterpillars — and even indicators that they’ve been there.  I haven’t had a lot luck in my a part of NY State, although an acquaintance dwelling on the shores of the Hudson River close by had nice success this final summer season with milkweeds she planted in her yard.

I’d like to learn you tales of Monarchs and different Nature associated experiences.

Starting your remark with “Kip…” will let me know that you’re ‘speaking’ particularly to me.

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