Regal fritillary surveyors Jan and Patty (l to r) at Barneveld Prairie.
It’s summer on the prairie, and that means the regal fritillary butterfly has taken wing in the Military Ridge Prairie Heritage Area in parts of Dane, Iowa and Green counties. The area is one of three strongholds in Wisconsin for this striking butterfly, which is endangered in all states east of the Mississippi River where it occurs, including in Wisconsin.
For 20 years, citizen scientists, clipboards in hand and sunhats on, have walked the summer prairies at Military Ridge along fixed transects (or paths) counting regal fritillaries and noting where they occur. They are helping The Nature Conservancy and The Prairie Enthusiasts understand the impacts of prairie management on this rare animal.
Regal fritillaries need prairies and other grasslands to survive. With the loss of historic prairie lands to agriculture, tree and shrub invasion and development, regal populations declined precipitously east of the Mississippi River from about 1970 to 1991. They were listed as an endangered species in Wisconsin in 1998. Regals appear to be doing better west of the Mississippi and have not yet been listed as an endangered species by the U.S. Fish and Wildlife Service.
While they are holding on at Military Ridge, Buena Vista Marsh, Fort McCoy and a few other places in Wisconsin, regal populations are still declining. The exact reason for this is unknown, but there are a few possibilities according to Rich Henderson, Research Scientist with the Wisconsin Department of Natural Resources. Rich is compiling and analyzing the monitoring data being gathered on Nature Conservancy, Prairie Enthusiasts and other grasslands at Military Ridge to try to get some answers.
“The population declines we’re seeing are not just in regals but in a whole suite of butterflies that require grasslands to survive,” Rich said. Loss and fragmentation of grassland habitat is definitely a factor. But some new type of disease and climate change could also be affecting these butterflies.”
Another concern is the impact that controlled fire could be having on the regal fritillary. Regals don’t migrate; their caterpillars spend the winter in the plant leaf litter and begin feeding on violets, their sole food source, when they emerge in the spring.
The Nature Conservancy, The Prairie Enthusiasts and other natural resource managers use controlled fire to keep prairies healthy. Fire helps reduce invasive species and woody brush, and it increases the diversity and vigor of the flowering plants that regals and other butterflies and insects need. But concerns have been raised that it could also be harmful to them.
“What we know so far,” said Henderson, “is that the year in which you burn, there are fewer regals. But the following year, you get a big rebound, most likely because fire has improved the habitat and there are more flowering plants. Eventually that boost to the habitat declines and the regal numbers do too.”
“Because there is so much variation in weather and moisture conditions from year to year,” Henderson added, “we can’t make any solid conclusions yet about the right amount of fire needed to maintain the prairie and the long-term survival of regal fritillaries. We need more data, not just from the established transect areas but throughout the entire area the butterfly uses as habitat at Military Ridge.”
Wisconsin Agriculture Strategy Fellow Paige Leytem, who is coordinating this year’s butterfly survey for The Nature Conservancy, reports great volunteer participation. And this year, volunteers are not only looking for regal fritillaries, but the rusty patched bumble bee, which was listed as an endangered species this year, as well.
“If we find rusty patched bumblebees on our land, we will consult with the U.S. Fish & Wildlife Service to ensure that our management practices won’t jeopardize the population,” Leytem said.
One of those volunteers, Jan Ketelle, has been helping with the regal surveys since their inception in 1997.
“The Nature Conservancy started a volunteer butterfly monitoring program in 1995, and I took the training,” Jan said. “I love being out in the prairies on a weekly basis seeing the different plants like Hill’s thistle, rough blazingstar and tuberous Indian plantain in bloom. It’s a lot of fun and makes a nice break from walking the prairies with a parsnip predator in your hand removing wild parsnip."
With the help of volunteers like Jan, we will continue to gather data that we believe will help us come up with some solid ideas on how to find the right balance of management so we keep regals in a healthy prairie landscape.