A Tough, Adaptable Survivor

In North America, there are lots of prairie species of conservation concern. Plants and animals that used to be more abundant and widespread than they are today are being squeezed by habitat fragmentation and degradation. On the other hand, there are also prairie species that are adapting very well to recent changes in the landscape and climate. We spend a lot of time worrying about the former. Let’s spend a few minutes celebrating one of the latter!

Orange sulphurs are more abundant today than they were 100 years ago.

The orange sulphur butterfly, also known as the alfalfa sulphur (Colias eurytheme), is one of the most abundant butterfly species in North America. It can be found through most of Mexico and all the way through much of Canada and Alaska. The species is variable in its appearance and there are many other yellow butterflies that look similar, are closely related, and that may even hybridize with the orange sulphur. That makes identification in the field very difficult.

If there’s any orange color in the wings, that’s probably an orange sulphur. If not, good luck. I think all the photos here are of orange sulphurs but I won’t be surprised or upset if someone points out that one is a clouded sulphur or something else.

The patch of orange on the top wings is a nice characteristic to look for when trying to identify orange sulphurs.

Getting away from mundane identification characteristics, the orange sulphur is a survivor and should be given credit for that. As other butterfly species have lost population size, the orange sulphur has increased its continental population significantly. Other species are found in few places than they used to be. The orange sulphur has apparently expanded its range (especially to the east and north) to fill up the continent. It doesn’t overwinter well up north, but can move northward each year from the south. Climate change seems likely to make that even easier in the future.

Why is the orange sulphur doing so spectacularly well? One reason is that its larva like to eat legume species, including lots of new ones we have introduced to North America. A big example is alfalfa (Medicago sativa), which the caterpillars really love – to the point where the orange sulphur is sometimes considered an agricultural pest in alfalfa production fields. Larvae also like to feast on sweet clover (Melilotus sp) and white clover (Trifolium repens), among many others.

There has to be more to the success story than just lots of food, though. Lots of other butterflies have abundant food sources but are experiencing population declines. Several prairie skippers that are rarely seen anymore use common grass species as larval hosts. Those grasses are everywhere – the butterflies are not. What else is the orange sulphur doing to thrive in a rapidly changing world?

I don’t know the answer to that. If we could figure it out, it might help us understand how to help other butterflies that aren’t doing as well as the orange sulphur. Habitat loss and fragmentation seem like obvious drivers of butterfly population declines, but again, those rare skippers – and other declining butterfly species – are often doing poorly even in parts of the continent where their prairie habitat seems relatively intact. Something else must be going on.

Pesticides are often listed as a major contributor to insect declines, and that seems fair, but a lot of orange sulphurs live directly in and around agricultural crop fields, where those pesticide effects should be highest. They also feed on white clover, which is abundant in urban yards where pesticide use can be very intense. Why are orange sulphurs still flourishing?

Here’s looking at you, orange sulphurs!

Regardless of the reasons, the orange sulphur seems to be doing great and we should be happy about it. It’s an objectively gorgeous butterfly, after all, and easy to spot and admire in the field. Despite that, I’ve occasionally caught myself occasionally thinking “Oh, that’s just another orange sulphur” when one catches my eye. A totally unfair response. Birders do the same thing, I know, with species like northern cardinals, American robins, or other species that have adapted well to our contemporary landscapes. We get numb to the beauty we see everyday.

We should be lauding the resilience and adaptability of these abundant native species. The fact that they’re common is a good thing, right? I guess white-tailed deer might be an exception to that rule. Their population numbers have skyrocketed since the early 1900’s and they are now causing considerable damage to ecosystems (and cars). Ok, fine. We have too many white-tailed deer. To my knowledge, no one has ever had to buy a new car after hitting an orange sulphur on the interstate. Let’s give these handsome butterflies a break and acknowledge their achievement!

In the movies, the tough, adaptable, resilient characters are the ones we root for. We should probably root for them in prairies too, huh? Abundance is a good thing. It’s not like orange sulphurs are stepping on the heads of other butterflies as they fight their way to the top. At least, not as far as I know. (Are they? Surely not.) Assuming they’re just finding ways to survive and doing it well, let’s all agree to celebrate their success. Maybe we can even figure out how orange sulphurs are doing it and see if there’s anything we can apply toward the conservation of species that aren’t thriving.

This entry was posted in Uncategorized by Chris Helzer. Bookmark the permalink.

About Chris Helzer

Chris Helzer is the Director of Science for The Nature Conservancy in Nebraska. His main role is to evaluate and capture lessons from the Conservancy’s land management and restoration work and then share those lessons with other landowners – both private and public. In addition, Chris works to raise awareness about the importance of prairies and their conservation through his writing, photography, and presentations to various groups. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press. He lives in Aurora, Nebraska with his wife Kim and their children.

2 thoughts on “A Tough, Adaptable Survivor

  1. what a great perspective. Next time I see one I will say, “Hello you little bad-ass survivor! Instead of thinking.. Meh.. another Orange sulfer. LOL

  2. These sulphurs are like Formica montana – Prairie Mound Ants among the prairie species of ants. The mound ants are literally dirt-common, even more so in disturbed and reconstructed prairies, but also are a keystone species. One wonders how many other prairie species are supported by these butterflies’ abundance?


Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.