Experimental management and mark-release-recapture methods fill critical knowledge gaps for an at-risk butterfly

Understanding how management actions affect target species is crucial for designing conservation strategies that meet recovery goals. In the context of Oregon silverspot butterfly (Speyeria = Argynnis zerene hippolyta) conservation, we used experimental habitat manipulations and mark-release-recapture methods to measure the effects of habitat restoration and population augmentation on butterfly vital rates. To understand the butterfly’s response to management, we (1) measured larval survival in response to invasive grass and thatch removal, and (2) used mark-release-recapture methods to estimate phenology, adult survival, and female egg laying of both wild and captive-reared butterflies. We found that reducing the density of invasive grasses and associated thatch, increased larval survival by up to 50%. We also found that wild butterflies emerged, on average, three weeks before captive butterflies were released and lived up to a week longer than captive butterflies. This mismatch in timing resulted in observations of only 15% of captive females laying eggs as opposed to 45% of marked wild females, suggesting that captive-reared females are contributing very little to the overall population. For Oregon silverspot recovery efforts to succeed, continued management of invasive grasses is key, as is further work to match the timing of releases of captive butterflies with flight of wild butterflies.

Through hands-on manipulation of habitat and marking at-risk butterflies, we identified specific ways to improve current management actions to meet recovery goals. These techniques are necessary for developing conservation strategies that will save species from extinction