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A Mystery – Rise to that?


Kip Hansen news summary – March 21, 2022

The wondrous wondrous Monarch butterflies are on the rise – they’re on the run – populations are skyrocketing! That means, according to the Monarch censuses, the number of Monarchs migrating east in both Western Migration and Eastern Migration has improved significantly compared to last year.

King Butterfly (Danaus plexippus) and theirs annual North American migration represent one of the mysteries of the animal kingdom, with their hitherto inexplicable ability to produce a generation each year capable of traveling up to 2,500 miles and then, even after Such a long journey for such a small insect, wintering without food, until spring, at which point they fly north again to feed and mate along the way.

Monarchs eat nectar, like other butterflies, but to reproduce, they need milkweed plant, on which they lay eggs. Although the milkweed plant is slightly poisonous, the monarch caterpillar will only eat the leaves of the milkweed plant. It is believed that changing agricultural practices to suppress weeds and the rampant mowing of highway banks have significantly reduced royal milkweed and contributed to a reduction in the number of weeds. their quantity.

And this last winter?

The Western Migration (and see the map above) shows a great comeback. According to Xerces Society, the migration to the West for the 2021-2022 season has been a great success with up to 250,000 monarchs found known winter locations along the southern California coast from Monterey south to San Luis Obispo. Xerces says that this is “a finish 100 times increase are from years ago total less than 2,000 monarchs and the highest total since 2016.

How can this be so? No one is really sure. For any closely watched annual natural phenomenon a 100-fold increase in a year is somewhat unusual.

That shouldn’t be unfamiliar to those familiar with real-world population dynamics, however. It is possible that the Western Kingdom population could function as an “island species”, where abundance or scarcity of resources and intra-species competition control species size. Under these conditions, mathematical formulas for population dynamics that show certain chaotic features, including population spikes and explosions (see graphic on Cloud Island Squirrel Population). The reality of this kind of chaotic behavior has been confirmed in the natural world many times over.

However, Monarchs are likely year-round in the southern parts of California and northern parts of Mexico and are found quite commonly living and breeding at all times of the year. This means that not all kings west of the Rockies participate in the annual migration. Many people just do what humans normally do, they move to southern California for the winter and go on with their normal lives. For monarch butterflies, that means mating, laying eggs, dying, and the new generation hatching like caterpillars that feed on milkweed and pupate to become the new monarch. Tagging efforts have shown that some Western Monarchs may even migrate to the same locations in Central Mexico as the Eastern Monarchs.

The fear of extinction for the Western Monarch is not about the actual extinction of the Monarch butterfly west of the Rocky Mountains, but rather the fear that the Monarch Migration of the West will cease to exist: ” …1983, IUCN took the unprecedented step of creating a new category in the Red Book of Invertebrates, to list monarch butterfly migrations as Threat phenomenon. This is because the number of Americans immigrating is plummeting. Figures for 1997-2016 show a 74 percent decline in wintering monarch species in California. “And last year, very few people who migrated to the West disappeared…. Almost non-existent.

Possibly contributing to the increase is quite a bit of action by civic groups in the West to plant succulents both in home gardens and on public land and to discourage roadside mowing there. This type of action is popular in the USKY also.

And the exodus in the Eastern United States?

Here we encounter data scarcity… .because of Covid! Usual sources of data: butterfly populations along the north-south migration route have been limited or completely abandoned due to (unfounded) fear of being in groups or even in some cases fear of being outdoors.

Last November, Monarch followers east of the Rocky Mountains had mixed opinions on how the season would turn out.

“Karen Oberhauser, founder of the monarch butterfly citizen science organization Monarch joint venture and professor of recovery ecology at the University of Wisconsin-Madison, said she is cautiously optimistic about summer spawning activity and anecdotal reports of high numbers seen in summer migrations. collect. “I hope … it translates into good numbers in Mexico,” she said. ” [ source ] In the same report, “Chip Taylor, founder of Monarch Watch, is less enthusiastic and thinks that the migratory population of the eastern monarchy will decrease this year. He points out that historically late migrations produced smaller wintering populations.”

The usual census data sources for the Eastern Monarchy Migration have been silent for the past 2 years – figures normally released in February by Mexico CONANP – Comision National de Áreas Naturales Protegidas. Last year there was no official announcement (that I could find). The Monarch holy sites in Mexico have officially closed to visitors because of Covid. I’m not sure how this has prevented rangers and researchers from doing their usual census, but either they didn’t, or it’s coming late.

Latest population data for eastward migration from winter 2019-2020:

I’m trying to get the official numbers for the 2020-2021 season – but no luck so far. The best I’ve found is Monarch Watch’s comment Chip Taylor in his post on 6order January 2022:

“Last year, my estimate of the total area was almost correct – 2.0 hectares compared to measured 2.01 ha. That’s more of a guess than a data-driven prediction, but I’ll credit it for being close. There are reasons to think I will close again this year and other reasons to anticipate that the number will be higher.” (said while predicting another population decline for the period 2021-2022).

I have information from local Monarch researchers in Mexico who report that CONANP may soon publish a census (not as of March 20, 2022).

I can only deliver this good news from an eyewitness account:

“But by our estimation, in Sanctuary of Cerro PelónYes Double of butterflies from last season. (personal communication – interpreting language differences)

Cerro Pelón Santuario (or reserve) is just one of the places where large herds of eastern migratory kings reside to winter. It is located in the mountains about 60 miles northeast of Mexico City:

The other major monarch sanctuaries are all in the same general area. Cerro Pelón is shown in the center. The main nests are in the yellow zone, with small nests scattered around in the shown support zone.

So we have an incentive but Partially and informally reported from the scene in Mexico, which gives us this general picture:

If our unofficial estimates for this year are accurate and verified, the monarchs of the East are making a slow but steady return. When and if CONANP releases an official number, I will make an update report.

Conclude:

The exodus of the Western monarchy, which was predicted to disappear completely last year, has created a “speakable” magic trick for all opponents, proponents of doom. and all that was lost. Experts and supporters are completely thrilled and bewildered by 100 times increase in winter 2021-2022. Seemingly impossible to some experts, only 2,000 migratory monarch butterflies have survived, only one per cent of which may have been females, which seem to have managed to breed up to 250,000 children in a single season (including multiple generations).

The exodus of Eastern monarchs is somewhat shrouded in fog created by the Covid pandemic with official census numbers missing and/or unreliable. Opinions from the monarchy in the United States range from optimistic to pessimistic. The partial information from the experts on the scene at Cerro Pelón gives us hope that things are at least stabilizing.

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Author’s comment:

The news from California is intriguing and the experts’ bewilderment is delightful. I think many professionals believe in being able to say “We told you so! Now the western monarch butterfly migration is extinct and it’s your fault.” [ here and here ]. In the beginning, with the Earl of the Monarch during Thanksgiving in California, everything seemed fine, but the experts are still groaning and refused to recover. I hope I have time to write a longer piece detailing the conservation efforts underway, speculating about biologically impossible population growth, and other fascinating aspects of the story. bigger than this.

Our onsite reporter is Joel Moreno Rojas, who along with Ellen Sharpoperate JM Butterfly B&B in Macheros, Mexico, adjacent to the Cerro Pelón reserve. “Business quickly turned Macheros into a popular butterfly tourist destination. …. directly employ more than a dozen people as guides, interpreters, cooks, waiters, drivers and housekeepers in winter, as well as 3-4 construction and maintenance workers all year round”. Maybe next winter, I’ll go and stay for a week or two.

In the meantime, be sure to plant some native milkweed in your flower garden this spring. If you’re on a local conservation group, ask them to advocate for state and national road maintenance agencies to replace roadside weed patches. If you have young children (5-15 years old), seek out monarch caterpillars, catch and raise them to adulthood and let your children witness the miracle of their transformation from caterpillar to butterfly. Yes online guide. Once the butterfly has emerged and the wings are completely dry, release the butterfly into the nectar-producing flowers in your garden. Take note – it will fly away in a day or so – so make sure your child knows this ahead of time.

Nature is full of surprises!

Thanks for reading.

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