Monarch butterflies adapt to survive

There is some good news, at last -- with some bad news. Yet, 2024 may determine their fate.

Photo by Joshua J. Cotten on Unsplash

It is only February and I am already thinking about the Monarchs returning.

If it is a normal year, the Monarchs would winter in about 11 to 12 mountain regions of Mexico and then start their return in March. Traveling 50-100 miles a day, they should reach their northern destinations by June.¹ Breeding takes place February to March as they begin their return to North America.

The Eastern and Western Monarchs are considered one species (Danaus plexippus) with no agreed subspecies designations in the U.S., despite their geographic and behavioral distinctions. They are the ancestors of all the Monarch butterfly species in the world. The Eastern and Western Monarchs are the only species that migrates.

The decimated populations of Monarchs is cause for alarm. It is hard to imagine a world without butterflies and especially the iconic Monarch. Maybe we will not have to if the resilient Monarch proves to be able to adapt to change, in combination with human efforts and government endangered species listing.

Eastern Monarch Populations are Adapting

News that Monarchs have been spotted in the southern U.S. this winter, rather than continuing on their migration to Mexico is a bit alarming, and alarming for Mexico where Monarchs fill the sky and it is a major tourist event.² Mexico is clearing the equivalent of ten football fields a day of rainforest where the Monarchs winter, in order to grow avocados,³ coffee, etc.

Observers and scientists report that the dedication of humans to planting milkweed to support the Monarchs has been so overwhelming that the Monarchs have decided to stay! There is an ample food supply and infrastructure for laying eggs, so maybe it was a smart move on the part of the Monarchs.

Ecologists disagree on the population numbers and the cause of deviations in migration patterns. One scientist, Davis, et. al, suggests that it is a parasite “OE” that is causing widespread death and it happens in high density areas which happen to be where humans have planted lots of milkweed plants for them.⁴ The milkweed plants that are being planted are often non-native species, but is seems the butterflies prefer the exotic species to the native species according to one avid Monarch conservator in Maryland.⁵

Another scientist found that the population in at least one place had increased by 30%. It is the winter colony areas that are in decline — Mexico and California. This research uses citizen-scientist counts of Monarchs to conclude that the summer populations may be making up for the loss of wintering populations.⁶ Populations in Ontario, one of the northernmost summering areas, are reported to be unchanged.⁷

Western Monarch populations are stabilizing but critically low

Unfortunately, the Western Monarch butterfly in the Western United States is suffering from reduced habitat, and is at only 5% of its population in the 1980s! Despite this decline, counts that just ended in January 2024 for the wintering season found 233,394 butterflies slight down from last year but at about the same as 2020-21 levels.⁸

Nevada proposed legislation in 2023 (AB 221)⁹ that would allow state agencies to take measures to protect Monarchs and other pollinators which they cannot now do. This bill would define invertebrates in the wild as “wildlife” and bring them into the scope of authority for the state agency that manages wildlife. Unfortunately it died at the end of the session in April 2023.¹⁰

The migration route of 1,000s of miles over a two month period is risky, too; and traffic collisions are one of the most common causes of death for Monarchs, but natural causes (being eaten by a bird) remain a high risk.¹¹

Monarchs on the Endangered Species List

The Monarchs were proposed for the Endangered Species List under federal law in 2014, but the report on their listing found that listing was “warranted but precluded” due to other national priorities.¹² I wrote about the legal status of Monarchs in November of 2022, awaiting the potential 2024 Endangered Species listing.¹³ In June 2023, the Department of Interior published its report on whether the Monarch butterfly warranted listing, and made a finding that it warranted listing. However, they did not yet make a determination of whether it is threatened or endangered under the Endangered Species Act, or whether it will be listed at all in its competition with other priorities.¹⁴

“A species receives the protections of the ESA when the FWS lists the species as "endangered" or "threatened." A species is deemed "endangered" when it is "in danger of extinction throughout all or a significant portion of its range. . . ." 16 U.S.C. § 1532(6). ” Center for Biological Diversity v. Norton, No. CIV 03-252 LFG/LAM, 4 (D.N.M. Dec. 19, 2005). A "threatened" species is defined as "likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range." 16 U.S.C. § 1532(20).¹⁵

There are a total of eight candidate butterflies awaiting a final determination by the agency. At this late stage in the current Administration it is likely that they will issue a determination in the flurry of “midnight regulations” as they are called. “Midnight regulations” are a dump of final determinations on the last day of the calendar year of a President’s Administration even if they are re-elected in November.¹⁶ If they are not re-elected the dumping of regulations is always massive. It is a way to wrap up the business of the previous Administration, but it is also a way to push controversial determinations to the next Administration so they have to address them, usually in litigation challenging the regulations for any number of reasons.

Ideally, we would see a determination by summer, when conservation plans could get underway to protect the species listed, reducing the likelihood that these decisions would be reversed by a potential different party incoming Administration.

Both parties engage in this tactic so it is widely accepted as the norm.

Humans

But once again, humans have intervened in the natural processes of the environment around us, but we just cannot help it. Whether our impact is bad or good we are going to have an impact. Only the Deep Ecologists suggest that all humans should just die and leave the Earth to return to its former majesty without us. But we have to remember that humans are part of the ecology not at war with it and our fate is tied to the environment and everything in it.

Humans are part of watching and monitoring Monarchs and there is a hemisphere-wide effort to count and report the first Monarchs as they migrate to get a better idea of their numbers and migration routes. This is a citizen-scientist effort by many organizations, such as this one.¹⁷

If humans intervene to help Monarchs and they start to enjoy exotic milkweed more than the local milkweed, then that is part of nature because humans are part of nature. Change is part of the environment and ecology and it is never the same so we should not think all change is bad. Nature moves in a circle. Black Elk is quoted as explaining, “The power of the world moves in circles.”¹⁸

So there is a bit of hope that the numbers of Monarchs are higher than expected, even though their migration routes seem to be changing and looked as if the numbers had dropped to dangerously low levels. Humans having an interest in watching, counting, feeding and saving Monarchs is probably its best defense. Having a listing with the Endangered Species List as threatened or endangered would provide synergy to these efforts and maybe give us some solid hope for the Monarch where we see all good news in 2025 and beyond.

1. https://www.fs.usda.gov/wildflowers/pollinators/Monarch_Butterfly/migration/index.shtml

2. https://www.nathab.com/central-america/monarch-butterfly-tour

3. https://cri.org/reports/unholy-guacamole/

4. https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2656.13678 (2022)

5. https://e360.yale.edu/features/monarch-butterflies-milkweed-home-breeders

6. https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.16282

7. Ethier (2020) unable to locate.

8. https://westernmonarchcount.org/western-monarch-count-tallies-233394-butterflies/

9. https://www.leg.state.nv.us/App/NELIS/REL/82nd2023/Bill/9951/Text

10. https://www.leg.state.nv.us/App/NELIS/REL/82nd2023/Bill/9951/Overview#

11. https://www.science.org/doi/10.1126/science.aat5066

12. https://www.federalregister.gov/d/2023-13577/p-72

13.

14. https://www.regulations.gov/document/FWS-HQ-ES-2022-0174-0002 file:///C:/Downloads/FWS-HQ-ES-2022-0174-0002_content.pdf

15. https://casetext.com/case/center-for-biological-diversity-v-norton-3

16. https://en.wikipedia.org/wiki/Midnight_regulations

17. journeynorth.org/monarch/

18. Black Elk (2000). “Black Elk Speaks: Being the Life Story of a Holy Man of the Oglala Sioux”, Bison Books https://www.goodreads.com/quotes/8648893-everything-an-indian-does-is-in-a-circle-and-that