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A debate around the state of Monarch butterflies

Monarch Butterfly
Peter Miller
Monarch Butterfly

We need to talk about Monarchs. Yes, it’s that time of year when I hijack the bird report to talk butterflies, and it’s come none too soon. Because some recent, diametrically opposed news items regarding Monarchs have a lot of us scratching our bug-loving heads. I know you good people are concerned about Monarchs, the iconic, big orange butterfly that migrates from the northern end of the continent to wintering sites in Mexico and California each late summer. You probably know their caterpillars only eat of the various species of milkweeds, and maybe you have some in your garden just for them.

But are Monarchs endangered? Threatened? Are they declining at all? That’s the question a lot of us are asking after some conflicting recent information. I’ll start with the International Union for the Conservation of Nature, a global body that maintains a “Red List” of threatened and endangered species. They recently listed the migratory subspecies of Monarch as “Endangered.” It’s important to understand that Monarchs as a whole are not going anywhere – there are stable resident populations throughout the New World tropics and even in Europe and other parts of the world – we’re talking the North American migratory subspecies. Also, this IUCN listing has no connection to the United States Endangered Species list, nor any legal standing within the US.

To give you an idea of how much the IUCN Red List affects U.S. policy, the Horseshoe Crab, still currently harvested to be used as bait here in Massachusetts and elsewhere, is also listed as Endangered on the IUCN Red List. So no one should expect to see any direct conservation action as a result of this non-binding, largely symbolic listing of the migratory Monarch. However, even the stodgy U.S. Fish and Wildlife Service has determined that listing the Monarch under the U.S. Endangered Species Act is “warranted but precluded.” meaning that it should be on the list but they don’t have the time and resources to actually do it, so they punted.

But there’s a scientific monkey wrench in the Monarch conservation machine. It’s a recent study by several prominent scientists who study Monarchs or butterflies in general. They looked at citizen science data from the annual July butterfly counts across the continent, like the ones I do here on the Cape, to look at Monarch trends since the early 90s. After some pretty complex statistical modeling, they declared that everything is fine with Monarchs because, while the wintering populations in Mexico and California have indeed decreased, the summer population is not declining overall, just in certain areas.

So the Monarchs are apparently able to repopulate as they move north despite lower winter numbers. Sadly for us, the area of greatest summer decline according to their study, is the Massachusetts to New York region. The other is the part of the Midwest with heaviest use of Roundup Ready crops, where heavy herbicide use has decimated milkweed populations. They say Monarchs are increasing in the southeast, northwest and upper Midwest.

One author, a University of Georgia scientist named Andy Davis who has been studying Monarchs since 1997, goes so far as to declare that Monarchs not only shouldn’t be listed as endangered, but that breeding, summer Monarchs don’t need our help at all! He says we just need to leave them alone, whatever that means. I disagree, mainly because helping Monarchs helps lots of other things, but also because a lot of us have issues with this study that the authors have not adequately addressed. So who’s right? Is the migratory Monarch subspecies knocking on the door or extinction or is everything hunky dory? The confusing part is that all involved in putting out this conflicting info are scientists trying their best to interpret the existing data.

As I write this, three Monarchs are bouncing around my yard, stopping by my various milkweed plants or butterfly bushes, as is typical in summer. I’m tracking 6 or 7 of their caterpillars on my milkweeds. I wish they could tell me the real story, but they wouldn’t have any idea because they are probably less than a week old. I guess we’ll have to figure it out for ourselves, but in the meantime, don’t stop helping Monarchs and other bugs. If you do, I’ll just keep bugging you with more insect-related “Bird” Reports.

Mark Faherty writes the Weekly Bird Report.