WisDOT Moves Karner Blue Butterflies by the Bushel
US Highway 10 cuts through the middle of Wisconsin, connecting the Fox Valley Cities in Wisconsin with the Twin Cities of Minnesota. This main traffic artery needed to be upgraded from a two- to four-lane expressway. Unfortunately, the new westbound lanes cut through a small 1/3 acre patch of Wild Lupine (Lupinus perennis) and native barrens habitat that was occupied by Karner Blue Butterflies (Lycaeides melissa samuelis) (view a picture of a Karner Blue Butterfly, a federally endangered species. Recent surveys indicated a population of at least 10-20 adults consistently bred on this tiny patch of habitat.
Habitat Conservation
WisDOT is part of a multi-partner Habitat Conservation Plan (HCP) for the Karner Blue. WisDOT accommodates Karners along about 500 miles of highway right-of-way in central and northwestern Wisconsin. After going through the usual mitigation negotiation procedures of avoidance and minimizing, it appeared there was no way this swatch of earth could be spared from the new lanes. Another question arose as to the future viability of the Highway 10 site for the butterflies. It was unrealistic that a site this small, surrounded by Eurasian weeds, in the presence of a major highway, would remain viable in the long term. During the mitigation process, WisDOT began to explore the possibility of moving the butterflies. Although ideas about moving butterflies had been written about, no one had previously done this in the wild.
Fortuitously, the Wisconsin Department of Natural Resources (DNR) just completed removing brush and most of the trees from an area near Emmons Creek, a lupine barrens community. Wild Lupine responded very well to the DNR barrens restoration effort, along with several other butterfly nectaring plants, but several surveys indicated that no Karners moved in to take advantage of the restored habitat. This presented an opportunity to move the Highway 10 population to the newly restored area.
The easiest way to move butterflies is in the egg stage. Karners conveniently lay almost all their eggs on the stems of Wild Lupine near the base of the plant. Methods included marking each Wild Lupine plant during peak flowering period, then after the egg laying period, clipping the Wild Lupine at the base of the stem with either a knife or clippers, gently laying the stems in large plastic bins and transporting the stems to the new site. The clipped stems were then inserted in the midst of living lupines at the Emmons Creek site. It seemed fairly straightforward, but there were a few questions. Would the eggs over-heat in the sun during the move and die? Would the eggs remain attached for the ride to their new home? After hatching, would the larva climb from the clipped stems to living plants?
Addressing Challenges
To help with these potential pitfalls, the bins containing the clipped lupine stems with the Karner eggs were not tightly covered and were shaded from direct sun light. Fortunately, the weather during egg movement was relatively cool, with cloudy, nearly windless days. It is believed these weather conditions helped preserve the eggs from overexposure during movement. Care was taken not to over-pack or crush the bins with lupine stems. Once cut and placed in the bins, batches were moved within an hour to the new site. During the clipping portion of the work, a number of eggs were observed (3-6 on some stems) and it was noted that a few larvae had already hatched and were actively feeding on the lupine. The clipped stems were placed in the middle of healthy plants at the new site with as much contact between each as possible.
About 120 pounds of stems and leaves were removed from the Highway 10 site. Once this movement was complete, it was time to wait for eggs to hatch, larva to pupate and form new adults. About six weeks after the move, surveys were conducted at the new site for adults. It was very gratifying to report that 42 adults were observed on the new site where none had been seen before. It appears that the larva did find their way to new lupine stems and successfully pupated to adult butterflies.
Lessons Learned
This process may have implications for other butterflies, and perhaps even other insects. If the host plant and egg laying process is known, capture and release of these species can be quite easy, with minimal disruption to the individuals themselves. This may also provide a method for population expansion to new areas, or at least within nearby, similar, ecological areas.