Monarch Update: Early Spring 2023

Guest Essay by Kip Hansen — 17 February 2023

The Marvelous Mysterious Monarch butterfly has been in the news again – some good news and some not-so-good news – at least, I  think so.

First, let me remind readers that the Monarch Butterfly, (Danaus plexippus plexippus), is found widely in many parts of the world, and is in no danger whatever of going extinct. 

You see that there are populations of monarchs in the South Pacific and Australia, all of the United States and much of southern Canada, All of Mexico, Central America, the northern coastal areas of South America, southern Spain and Portugal, the Spanish and Portuguese Atlantic islands (Madeira, Azores, Canaries) and parts of Morocco.

However, you will have read (if you read any newspaper or watch any news programming or any nature programming) that the IUCN has “declared the Monarch Butterfly endangered.”

It should not shock readers here that this is Not True.  That means, quite literally, False.  False as in the IUCN has not declared “The Monarch Butterfly” to be endangered.  Confused yet?

So, what’s the real deal?  The IUCN, in July 2022, declared “Migratory monarch butterfly now Endangered”.  The fact is that they have declared the phenomena of the two migratory populations of Monarch Butterflies in the United States and Canada, each of which migrates each winter to areas with milder winter conditions, to be endangered.  With the simple trick of pretending or declaring that the migrating populations are “sub-species”, they make it look as if the Monarch Butterfly is endangered.

The Western migratory population migrates to the coastal mountains of California, from Monterey Bay south to the border with Mexico.  They come from as far north as southern Canada.

Although, as you can see at the bottom right, some sneak off to the overwintering sites in Mexico of the Eastern population (they do this even from Southern California).

So, what is the situation with the Western Monarch Migration?  The best data comes from the Thanksgiving Monarch Count and the New Year’s Count — the Thanksgiving Count ran from 11/12/22 – 12/4/22, and the New Year’s Count ran from 12/24/22 – 1/8/23.

Here we see the near-extinction of the migration in 2020, with numbers so low that they barely show on the bar chart, now, this last winter’s counts show the Western Monarch Overwintering population has recovered to levels seen in the early 2000s.  That’s good news.

The not so good news is that the overwintering coastal areas of California were hit with recurring winter storms (the now-famous atmospheric rivers) — after the January count — and the effects the storms had on monarchs is unknown.

The Eastern population of monarchs has a more spectacular migration:

The Eastern monarchs migrate a much longer distance than the Western monarchs. This map also shows the percentages of monarchs from each area, with the highest percentage coming from the Midwest’s vast acreage of agriculture.

There are worries that the bad weather and cold snaps in Texas last fall, as the monarchs were passing through enroute to their Mexican overwintering grounds, might have greatly reduced their numbers.  We really don’t know yet, as the Mexican authorities are a bit secretive with the exact location of overwintering sites and maybe a bit slow with their official counts, which are done in conjunction with WWF.

Reports from one overwintering site in Mexico, El Rosario, indicate the numbers may be lower this year (YouTube)  than last year and that warmer than normal January temperatures have caused the monarchs to be over-active, flying about, and drinking, several weeks earlier than usual.

Orley “Chip” Taylor, the padrino of the monarch butterfly conservation,  with, is quite pessimistic for the numbers in Mexico for the 2022-2023 winter, and gives his reasons in a long technical post at MonarchWatch.

Estela Romero  gives two eye-witness reports from Mexico, representing two of the many known monarch roosting sites:  1)  at the Sierra Chincua Sanctuary, in early January, “the colony’s population seems to be smaller compared to the colony’s size last year.”  2)  and at the “El Rosario Sanctuary, which typically is home to the largest overwintering colony, shows a beautiful but smaller area of occupation.”  There are over a dozen recognized monarch overwintering sites:

(click here for a larger view)

Mexico City can be seen at the far right.  The two sites reported by Estella Romero in in the center of the map, one above the other. 

We won’t know the official numbers until sometime in May when the WWF (WWF International, WWF Mexico) in collaboration of the National Commission of Protected Natural Areas of Mexico, the Mexican Autonomous National University, and the WWF Alliance-Telmex Telcel Foundation, releases the count (as number of hectares occupied by monarch roosts all combined).  Last year, May 2022, the count was up 35%

Up to last winter, there was hope of a lasting and growing recovery:

This year?, we’ll have to wait and see. 

Bottom Lines:

1.  Monarch butterflies are not endangered – there are a whole lot of them and they live in many areas of the world. In the U.S., not all monarchs migrate at all — many monarchs just live in Southern California and the U.S. South, including Florida and Puerto Rico, continuing to breed and skipping the migration altogether.

2.  The fascinating behavior pattern of the two sub-populations in the United States that migrate to milder climates and congregate in huge roosts over the winter has been losing steam for many years, with fewer monarchs participating. 

3.  In 2020, it looked like the Western Migration was doomed to end forever.  But, nature, as it is prone to do, surprised all the doomsayers and staged a truly miraculous recovery – increasing from 2000 to 3000 overwintering butterflies to over 200,000 in one season.  That sub-population has maintained that recovery this winter growing to over 300,000.  The overwintering roosts on the California coast may have been hit hard by the storms this January.

4. The Eastern monarch migration is still in trouble, but has improved the last few years.  This year is still an unknown, but the prognosis is not healthy.

5.  You can help preserve this interesting and little-understood phenomena by following advice for boosting monarch numbers in your area, for example: Monarch Joint VentureSave Our MonarchsBetter Homes and Gardens.

# # # # #

Author’s Comment:

First, hat tip to Robert Hains, who sent in the Story Tip that led to this essay.

The U.S. Monarch migrations are  mind-boggling phenomena (phenomenon, if you prefer).  Read about it in my earlier posts here at WUWT.

You can help the monarchs recover by planting native milkweeds in your home gardens, encouraging your local Highway Departments not to mow milkweed patches on the verges of roadways,  encouraging your local Parks Departments to plant native milkweeds and butterfly gardens in your parks.

Finding and protecting Monarch chrysalises is helpful  as long as you follow instructions and release the butterflies once they have emerged.  This is particularly great if you have kids. 

This really is one problem where a little effort from lots of people can make a difference.

Thanks for reading.

# # # # #

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February 17, 2023 6:09 am

I’m headed down there on the 20th. Most of the sanctuaries are reporting slightly increased numbers.

Reply to  Kip Hansen
February 17, 2023 9:05 am

I hope they are all snuggled away in some nice and warm place, Judging by the most recent SSW spike, the USA might be for another cold weather shock possibly worse than one from the few weeks back
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Reply to  vuk
February 17, 2023 4:25 pm

Yep! This is according to Joe Bastardi.
Joe Bastardi


Except for the cold December start, the WPO and NAO have been positive much of the winter, They are both forecasted negative for March, a rarity to see them in tandem like that. 3 times in 40 years and only one time, 1984. was there a Feb stratwarm.

February 17, 2023 6:31 am

When using acronyms, such as IUCN, WWF, even with a hyperlink, it is best to not assume your readers know them and explain them in the first use in the article.

Last edited 1 month ago by murphyj
Reply to  Kip Hansen
February 17, 2023 8:17 am

What has the World Wrestling Federation got to do with climate change – damn they’ll blame NASCAR next

Reply to  Bil
February 17, 2023 8:43 am

You know the thing about bugs and windshields.

February 17, 2023 6:48 am

Bottom line… we have to come up with a species related scare. Any ideas? How about the Monarch butterfly?

2013 – Mexican monarch butterfly numbers at record low, scientists say – The Guardian
2014 – Monarch butterflies keep disappearing. Here’s why. – Washington Post
2015 – Neonicotinoid link to Monarch butterfly decline – The Ecologist
2016 – Great monarch butterfly migration mystery solved – BBC News
2017 – There will be fewer monarch butterflies this year. 22 million fewer. – USA Today
2018 – We’re losing monarch butterflies fast—here’s why – National Geographic
2019 – Monarch butterfly populations are on the rise – WWF
2020 – The Monarch butterfly’s unexpected population growth has surprised scientists – MSN
2021 – Why is the eastern monarch butterfly disappearing? –
2021 – Eastern monarch butterfly population shows signs of recovery – WWF
2022 – Monarch butterfly counts rise in Colorado and beyond, but extinction concerns remain –
2022 – Data on Monarch butterflies in 2022 show a sharp increase in their numbers. – The Yucatan Times

On second thoughts, nah.

Reply to  Kip Hansen
February 17, 2023 8:21 am

Another problem is the uncertainty

February 17, 2023 7:00 am

One wonders how they “know” where to go (the migrants were never in the ultimate migration locations). Has to be some kind of genetic “map” imprinted in their tiny brains. I purposely plant field milkweeds here for their caterpillars.

Reply to  Kip Hansen
February 17, 2023 8:59 am

I just read a couple of interesting articles about the Monarch in Australia.
It’s an invasive species over there, first spotted in Sydney around 1871.
Also the Monarchs over there don’t rely on Milkweed, but rather plants that were introduced from Africa, southern Asia and the Caribbean. These plants all have the same poison in their sap that the Milkweed does.
Once again, some populations migrate and others don’t.
The other interesting thing about migration is this. Whatever mechanism the Monarchs used here in north America, seems to have adapted to Australia within a couple of generations.

Last edited 1 month ago by MarkW
Gunga Din
Reply to  Kip Hansen
February 17, 2023 2:31 pm

My “backyard” when I was a kid was acres of bulldozed land. (The developer apparently bought some land nearby that needed to developed quickly leaving my “backyard” a kids’ paradise for several years.)
Lots of milkweeds and pokeweed. (Pokeweed leaves a nasty purple stain that was of more concern to Moms than kids. We used the branches as swords!)
Anyway, when I was a kid we thought that milkweed sap would remove warts.
Don’t know if there’s anything to that.

Gunga Din
Reply to  Kip Hansen
February 17, 2023 3:15 pm

Maybe more irritating to warts? 😎

Last edited 1 month ago by Gunga Din
Reply to  beng135
February 17, 2023 9:33 am

Maybe they know something about tectonic plates crunching we don’t :
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Reply to  vuk
February 17, 2023 10:22 am

It’s extremely unlikely they would have any mapping bio-system.

“By far the most important sense for butterflies is smell—the sensors on their antennae are highly attuned to odours…
They operate on a system similar to a lock and key. When a particular chemical runs into a chemoreceptor, it fits into a “lock” on the nerve. This sends a message to the nerve cell telling the butterfly that it has encountered the chemical….
Adult butterflies sense most smells through their anten­nae, which are densely covered with chemoreceptors, especially on the clubs.
In monarchs, chemoreceptors on the antennae sense the odour associated with nectar and feeding as well as pheromones released by the male.

Let’s assume that the2 crunching of tectonic plates just of SW Mexican coast releases concoction of gases, spread by winds in all direction, to which Monarch’s antennae are extremely  well attuned to.
Only things Monarchs need to do follow smell to the source when migrating to the south, or getting away from it migrating to north (this is more problematic) avoiding sea or ocean.
Probably load of nonsense (you read it here first), but is as good a hypothesis as any I came across,

Reply to  Kip Hansen
February 17, 2023 12:44 pm

Hi Kip
Thanks for replying.
I suggest not to take it seriously, just a crackpot idea.
I thought about it and have looked in some detail about the area and description of the places.
To make hypothesis credible, if you are inclined to waste more of your time, I would postulate, rightly of wrongly, any gasses would be coming
trough cracks in land, and considering depth of the tectonic plates and slippage along the plate might be many miles away from the fault line.
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Map of Mexico showing locations of large strato volcanoes (open triangles), silicic caldera complexes (open circles), and monogenetic fields (stippled). El Jorullo (EJ) and Par ́cutin (P; filled triangles) are shown within the Michoac ́n –Guanajuato monogenetic field (MGMF). 
For this hypothesis of particular interest is the unique Guanajuato monogenetic field (MGMF). 
It appears that is the area where Monarchs go.

See: Bikepacking: Guanajuato to the Monarch Butterfly Preserves

One or two authors said that Monarchs go to mountains to ‘goldilocks’ climate places which again may be in reasonable proximity where gases may be vented,
Monarchs may go beck millions of years when Mexico climate and flora may have not stipulated migration, and distinct atmospheric ‘odour’ became part of natural instinct.
If so no magnetic, solar or any other kind of mapping would be necessary, just follow the ‘smell’, you might say.
Good reason why they would behave differently when roosting elsewhere including California it is not part of naturally developed instinct going back millions of years.
As climate gradually changed migration to and from their ‘homeland’ became a necessity. 
Thanks again, I enjoyed writing all that.

Last edited 1 month ago by vuk
Reply to  vuk
February 17, 2023 12:56 pm

Michoacán–Guanajuato volcanic field is located in the Michoacán and Guanajuato states of central Mexico. It is a volcanic field that takes the form of a large cinder cone field, with numerous shield volcanoes and maars.
The Michoacán–Guanajuato volcanic field covers an area of 200 by 250 kilometres (120 mi × 160 mi), in the states of Michoacán and Guanajuato. It contains 1400 vents, mostly cinder cones. 

Reply to  Kip Hansen
February 17, 2023 1:47 pm

Kip, your map shows major roosting areas just NW of Toluca

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while the volcanic MGMF is adjacent to it.
It is centred in and around the rectangle in the centre of this map

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The Michoacan – Guanajuato volcanic field is one of the most prolific monogenetic volcanic fields in the world. Its activity has been relatively recent with two new cinder cone complexes within the last 300 years. Monogenetic shield volcanoes, while active longer, are also relatively recent, as are lava flows that do not have a readily identified source (fissure eruptions). The area continues to be seismically unstable as the subduction and slab tearing action continues to jostle, rotate, and rearrange the three primary crustal blocks involved (Pacific, Cocos and Caribbean, see map I linked to, further above)

Last edited 1 month ago by vuk
Ron Long
February 17, 2023 7:09 am

I’m guessing the Biden administration will declare the Monarchs arriving from Mexico to be “Climate Refugees” and give them a cell phone and a voucher for $1,000.00 of food, and ask them to check in sometime, if it’s convinent.

Reply to  Ron Long
February 17, 2023 9:02 am

As long as he doesn’t give them the right to vote.

abolition man
Reply to  MarkW
February 17, 2023 9:40 am

I would think that we’d want them to vote; they live in the real world, and are at least as intelligent as the average college student! When was the last time you heard of a monarch trying change their gender?
It’s possible that they are right wing domestic terrorists; how many appeared at BLM marches or participated in the mostly peaceful riots? The implications are clear!

Caleb Shaw
February 17, 2023 7:50 am

Very interesting, Kip. Thanks.

I’m musing about what makes a butterfly “decide” to migrate. Perhaps they have a choice, and there was something going on out in California that decided most monarchs against migrating. Then, several generations later, the situation changed, and many more “decided” to migrate.

The “wooly bear” caterpillar apparently can “choose” not to pupate, and can remain a caterpillar up to seven or eight years, in especially hostile conditions. (One of the odd things I learned studying sea-ice and the arctic coast.)

I was down in Myrtle Beach one October when the monarchs were passing through on their migration. I was in the pines, looking up through green boughs to blue sky, and orange flakes of flame were fluttering over at the level of the treetops. They were not crowded, but at any given moment between one and three could be seen against that blue sky. Really one of the quieter and more lovely beauties I’ve ever been lucky enough to witness.

Reply to  Kip Hansen
February 18, 2023 6:51 pm

My experience of Monarchs comes from the Whitsunday Islands of the Oz great barrier reef. The first time I witnessed them flying in hundreds from one island to another. It was across about 10 miles of open sea, with a cross wind of about 15 knots. I was amazed to see them all laying off against the wind enough to make good a straight line from one to the other island. I witnessed this a number of times, but always in the same direction. It may have occurred the other way, but I was never there when it did. They must have been flying at considerable speed to make the crossing in that wind.

The other was at a small isolated island. This had an are that would be flooded for some months in the wet season. It was very open forest of trees like the paper bark that can stand water logging for some months. They generated a high semi closed canopy with grass & scattered stunted or dead small trees in the shaded area.

Walking through the area it appeared as if the small trees were in full leaf, but approaching closer the leaves suddenly took flight, filling the air with blue monarchs. I never saw them flying to or from this island, but I was not there often.

As the vegetation on each island can be very different I assumed that some may be favored breeding grounds with suitable flora, but that is just a guess.

Gunga Din
Reply to  Caleb Shaw
February 17, 2023 1:59 pm

OT and personal, I’ve noticed your name popping up recently.
Glad to see it.

Right-Handed Shark
February 17, 2023 8:14 am

The biggest threat to butterflies, and indeed all winged insects, as well as bats, birds and ocean life too:,the%20risk%20zone%20of%20turbines.

Dave Andrews
Reply to  Right-Handed Shark
February 17, 2023 8:45 am

A German study estimated that wind turbines in Germany killed billions of flying insects every year. Michael Shellenberger contacted the author of the report but was told he was not able to speak about it. He then contacted the authors institute and was told that neither they nor the author could give him further information.

Krishna Gans
Reply to  Dave Andrews
February 17, 2023 10:02 am

If I remember well, it was a study of the DLR 2019
They spoke about billions of insects, ca. 1,200 metric tons.
Of course, these estimations were declared as wrong. 😀

Dave Andrews
Reply to  Krishna Gans
February 18, 2023 5:55 am

Thanks for those links.

Rud Istvan
February 17, 2023 8:24 am

Kip, thanks for this. Until your post, I thought monarch’s were unique to North America and that all migrated. Very wrong on both counts.

Rud Istvan
Reply to  Kip Hansen
February 17, 2023 1:59 pm

Yah. Me. Just like I got polar bears from Susan Crockford. I did the pika and red wolf things myself researching essay No Bodies for ebook Blowing Smoke. But it is impossible to research everything climate everywhere. Again, many thanks for the lesson now learned. BTW, Jim Steele might like to repost this on his blog.

Reply to  Kip Hansen
February 17, 2023 2:12 pm

I was the guy that sent in the tip and I got a lot out of it. Thanks so much.

When I was in 6th grade we had a plant with a cocoon on it in a jar. The teacher had apparently caught a caterpillar, and realizing what it was kept it in a jar with a small plant and it made it’s cocoon on that plant. It was kept on the ledge in a window. We got to watch the transformation as the Monarch butterfly hatched. And then let the butterfly go.

It was a learning experience I never forgot.

Reply to  Kip Hansen
February 17, 2023 4:27 pm

Heck man, that was back in 1961! Anyway that was back when teachers actually taught!

How many of us can remember things that effected our development that can’t remember the names of those that did so? I suspect there are a lot for many of us. I wish I could remember her name.

I was living in a neighborhood at the time that was less than desirable. But that teacher was teaching.

Then my Dad had done well in his business. We moved to an upscale neighborhood when I had completed 2nd grade at the old school.

It was decided that I would take 2nd grade over again at my new school because the curriculum was so far more advanced than the school I had been attending before.

Last edited 1 month ago by rah
Gunga Din
Reply to  Rud Istvan
February 17, 2023 2:11 pm

Same here.
Nothing wrong wit learning something new.

John Hultquist
February 17, 2023 8:49 am

Thanks, Kip.
In my central Washington State location, I see a few Monarchs but more likely see Yellow Swallowtails, and Fritillaries. There is a small yellow butterfly that visits Rabbit Brush in late summer. Number-wise, this is my most numerous visitor.

abolition man
February 17, 2023 9:54 am

Great post, Kip!
I plant potfuls of butterfly flowers every monsoon, but I’ll try to add milkweeds to the mix this year.
I used to make at least one annual trip to Natural Bridges to see the overwintering monarchs when my daughter was small. I also remember seeing them in Pacific Grove when I was young.
We don’t see many monarchs here in the high desert, but I did have a Tiger Swallowtail that was visiting my hummingbird feeders for about a week a few years ago! I wouldn’t mind at all if that behavior became more common!

Elliot W
February 17, 2023 11:11 am

Save the Monarch Migration! No wind turbines!

Elliot W
Reply to  Kip Hansen
February 17, 2023 2:03 pm

Nope! It was a catchy sound bite! Find something photogenic to show the public and save it; a proven strategy.

However, other commenters have posted articles on numbers of flying insects purportedly killed by turbines, so it’s a question to explore if migrating Monarchs are being decimated by turbines.Has anyone even asked that question? Or is “climate change” the only acceptable answer to any population decline?

Elliot W
Reply to  Kip Hansen
February 17, 2023 10:05 pm

Seems to me it’s a question worth asking. I don’t know at what altitude they prefer to fly while migrating, but understand they need to come down to roost at night. So they may be vulnerable.

Gunga Din
February 17, 2023 1:56 pm

Thanks, Kip. I honestly didn’t know that Monarchs were not just a North American butterfly.
From the first map it seems that they are all over the place!
Kind of reminds me of a fish in Ohio. Some freaked out about. (Scioto Madtom?)
Long story short, a particular tiny catfish from a particular stream, the Scioto, was becoming less common. Tons of other Madtoms in other neighboring streams.
Even shorter, Madtoms are fine in Ohio and the Midwest.
But developments along the Scioto in Ohio have been hindered.

February 19, 2023 8:11 am

The overlooked issue here is what favorable conditions existed prior to the 1995 to 1997 peaks? The overwinter and forest area counts show increasing trends until dropping afterwards. Is the “decline” actually part of a cyclical pattern, meaning are we being misled due to a cropped timeline?

I didn’t know Monarchs were so widely dispersed across the planet. This demonstrates to me the US education system is truly crappy.

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