Butterfly Aggression

We started seeing our first regal fritillary butterflies of the season last week, and began our second year of data collection on their habitat use in the Platte River Prairies.  As always, male fritillaries have emerged first and now have to wait a couple more weeks before females arrive on the scene.  In the meantime, they do some nectaring, but mostly seem to just fly around.  They look like a bunch of teenage boys who arrived at the school dance before the girls…

A regal fritillary butterfly seen last week in the Platte River Prairies, Nebraska.

The above regal fritillary was nectaring on a plant that will remain a mystery until my next post (sorry).  I was expecting to see them nectaring on common and showy milkweeds (Asclepias syriaca and A. speciosa) because those plants were just starting to bloom.  In some studies of regal fritillaries, milkweeds are major nectar plants.  Last year we saw regal fritillaries using hoary vervain (Verbena stricta) more than anything else, but I didn’t see a lot of milkweed blooming last year – for some reason.  This year, I figured maybe we’d see something different since milkweeds seem to be having a good year.

As I walked around checking milkweed flowers for butterflies, I saw a number of insect species using them, but none more abundant than the gray copper butterfly.  In fact, I saw one flower that had six coppers on it at the same time.

A gray copper butterfly on showy milkweed. The Nature Conservancy's Platte River Prairies, Nebraska.

I did see a few regal fritillaries nectaring on milkweeds, but surprisingly few, given the high numbers of both fritillaries and milkweeds I was seeing.  Eventually, I decided to just sit for a few minutes in front of one milkweed plant to watch the gray copper butterfly that was nectaring on it.  I figured I’d get to see a parade of other insects come by and nectar there as well.

I saw a fritillary making its way toward the flower and got my camera ready so that I could capture both the fritillary and the copper on the same flower.  However, when the fritillary got within a few feet of the flower, the copper suddenly erupted off the flower and flew straight at the fritillary, chasing it like a small bird chases a hawk.  The fritillary swerved off and sped away.  I saw the same thing happen twice more within the next several minutes.

What looks like a peaceful scene with a pretty butterfly nectaring on a flower belies the bottled up aggression waiting to boil over when another butterfly strays too close...

Throughout the day, I saw the same aggressive behavior by coppers on other milkweeds as well.  It’s hard to say, of course, whether the coppers were really protecting their nectar source, but that’s what it looked like to me.  There has been considerable discussion in the scientific literature about whether or not male butterflies (of some species) defend territories like birds do – keeping other males away.  There seems to be consensus that at least a few species do.

What I was seeing, though, was not mating territory defense.  Assuming that coppers can recognize the difference between their own and other butterfly species, they didn’t appear to be chasing away potential competitors for mates.  Instead, they appeared to be monopolizing a valuable food source.  Even when there were multiple milkweed flowers on a plant, or several plants in a clump, coppers successfully chased fritillaries away as they approached.  Interestingly, while coppers wouldn’t tolerate fritillaries, they didnm’t seem to mind sharing flowers with other coppers…  There weren’t many individuals of other butterfly species around, so I didn’t get a good feel for whether coppers chased away all other butterflies or just fritillaries.

I’ve not seen or heard of this kind of behavior before, but I’m sure other people have.  I’d sure appreciate hearing from you if you know anything about it.

Aggressive butterflies… who’d have thought?

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About Chris Helzer

Chris Helzer is an ecologist and Eastern Nebraska Program Director for The Nature Conservancy. He supervises the management and restoration of approximately 4,000 acres of land in central and eastern Nebraska - primarily along the central Platte River. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press.
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23 Responses to Butterfly Aggression

  1. Stephen Winter says:

    Last week and the week before we started seeing fair numbers of Regals down here in Pawnee County. One place we were seeing them concentrated was on the roads (graveled with white rock) within Burchard Lake WMA, which were moist from recent rains. We guessed they were getting minerals from the moistened road surface.

  2. Stephanie Frischie says:

    That’s a special observation of amazing behavior. I wonder why the regals don’t push back?

    • Chris Helzer says:

      It’s interesting isn’t it… I suppose maybe the regals are like hawks being chased by smaller, more agile birds? Hard to fight back, and easier to just find another flower?

      • Randy says:

        I live in southern Rock Island County Illinois and they are even chasing our hummingbirds away very aggressively even as far as 20 or 30 yards. I have never seen this behavior ever in a butterfly.

  3. Jerry Ziegler says:

    I wonder how many butterfly species do this? We have a gravel boat launch where, as Stephen Winter observed above, butterflies congregate. I also figured that they must be after the minerals in the moist gravel. It’s a great place to do butterfly watching and looks for all the world like a pasture, but instead of cattle, it’s butterflies. I’ll see giant swallowtails and eastern tiger swallowtails grazing side by side with five or six “summer” spring azures an inch or so away and pearl crescents a little farther away. None of them minds the presence of the others.

    • Chris Helzer says:

      Good question. First time I’ve seen it, and I’ve seen the kind of mult–species mineral feeding behavior you mention too. I don’t know if it’s certain species or certain situations that lead to aggression – or both? (Or neither, and I’m just delusional!)

  4. James C. Trager says:

    Hackberry butterflies are notoriously territorial, chasing after just about anything of any size that flies by. If a person comes by, they fly out and light on him/her to drink sweat, a source of mineral nutrients.

  5. Dan Staehr says:

    Red Admirals are also territorial, much like male hummingbirds.

  6. Eleanor Burke says:

    I live in the westside of San Antonio Texas. We have had many Monarchs and Gulf Fritillary lay their eggs on our Milkweed. I was surprised to see the Fritillary attacking the Monarchs on two occasions. The Monarchs had just emerged from the chrysalis and were drying their wings when the fritillary attacked. The Monarch finally managed to get away. Very disturbing since I never imagined that butterflies were aggressive.

  7. Brian Murphy says:

    I just saw numerous Aprodite fritillaries attacking a lone Monarch that tried to feed on the same or nearby milkweeds. The fritillaries would feed side by side with each other, but if the Monarch came into sight at all they left the milkweed and mobbed the Monarch. Then I saw the friitillaries do the same thing to a Diana (again larger than themselves), but they paid no attention at all to a smaller Silver-spotted skipper. As mentioned in another post, it is almost like small birds mobbng a larger hawk!

  8. Susan haney says:

    Thanks for your post…I’m glad to know I wasn’t imagining things. Yesterday I was watching my butterfly bush and it looked like a monarch and a fritillary were competing for it. one would be feeding and the other would dive bomb, chasing it around the yard. I even saw two monarchs join together to chase the fritillary,

  9. Kathleen says:

    A man I work with asked me why a butterfly was acting in an unusual way- not only sticking around very specific parts of his yard, but was also not afraid of people, allowing him to walk right up to it and look it over. The biggest surprise was his account of it repeatedly chasing off dragonflies! I’m working on ID’ing it; perhaps this is the culprit… I could see defending resources from competition, but harassing predators? Strange.

  10. Batya Weisskoff says:

    I live in Miami and I’m new to raising butterflies, but within a few weeks have lots of monarchs and fritillaries. On two occasions this week I’ve observed a fritillary attacking a newly emerged monarch (flying close and even landing on it), making the monarch flap its wings before it was ready to do so. In both cases the wings of the new monarch were damaged. One seemed to recover and the other couldn’t.

  11. Tom H. says:

    OK ever seen a Skipper, specifically the Common Banded Skipper chase away a Humming bird (Female Ruby) ? I have a White Crepe Myrtle next to a Humming Bird feeder. If the Humming bird approaches to feed the skipper will chase it away. Here is an instance of an insect chasing off a bird!

  12. Stephanie Glasure says:

    I have developed a garden filled with Milkweed and many nectar flowers in order to try and encourage Monarchs. Yesterday, I spotted a Monarch and was very relieved and happy. Then, four Spangled Fritillaries chased the Monarch away. This happened several times. We have a very large population of Frittillaries and I am wondering if they will prevent the Monarchs from laying eggs?

    • Chris Helzer says:

      Stephanie, it’s a good question (and a fun observation!) I don’t know if the Fritillaries will prevent the monarchs from laying eggs or not. You’ll have to let me know what you find out!

  13. denise westlake says:

    Brandon Florida: just watched swallow tail chase monarch away. There are SSooooo many flowers to go, certainly enough for all to share. Kindof sad..

  14. Ann says:

    I dug up my maypop vines today because the gulf fritillaries are so aggressive with the monarchs I raise. The frits have attacked many monarchs in my yard…not just chase the monarchs away but 2-3 frits at a time cling on and subdue a single monarch. This is just the second year I have noticed such aggressive frit behavior.

  15. Steven M. says:

    Orlando, Fl: Built a butterfly garden earlier this year, mostly pentas and milkweed for butterflies, but also a purple sage and sweet almond plant for the honeybees. We have a lone monarch that will chase other monarchs, dragonflies, and even birds out of our yard, diving on them all! This may be the same monarch we witnessed being attacked by wasps early in the season, which may be the source of its aggression. There are some moths it will not pursue, but I believe that is because they are smaller. The monarch does not seem to be bothered by humans.

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