Endangered Oarisma poweshiek butterfly larval foraging and adult habitat interactions in Manitoba, Canada

The Poweshiek skipperling (Oarisma poweshiek) is endemic to the tall grass prairie in North America, and is now critically endangered globally. Existing populations are scattered amongst tall grass prairie remnants. However, the host food plants eaten by Poweshiek skipperling larvae, the vegetative and microclimatic descriptions of immature and adult microhabitats as well as O. poweshiek behaviour in Manitoba are unknown. I observed the foraging behaviour of larval O. poweshiek in natural habitat to determine the plant species that they consume and document their development. I also followed adults in prairie patches to identify locations in which various activities, such as egg laying or nectar feeding, were facilitated by the habitat. I measured vegetative, structural and microclimatic attributes of microhabitats to determine potential characteristics which facilitate various adult activities and larval development. Larvae appeared to navigate microhabitats to locate host food plant species, alternating between shoots of various species throughout their development. Adults flew almost exclusively in the prairie plant community, rarely flew in shrub or ephemeral wetland communities and were never observed flying in wetland or forest communities. Adult activities appeared to be distributed along a soil moisture gradient, with egg laying associated with the mesic section of the moisture gradient, resting and/or basking associated with the drier section and nectar feeding generally associated with sections throughout the moisture gradient. My research contributes knowledge about larval O. poweshiek foraging and adult habitat interactions in prairies in Manitoba, Canada. Discoveries from my research may guide habitat stewardship to ensure that high quality habitat is available for every life stage and inform reintroduction activities to ensure potential release locations contain required habitat features. Novel descriptions of locations which facilitate larval development and various adult activities may inform provincial and federal recovery strategies to increase the chances of O. poweshiek’s survival. My findings may also initiate further research about the Poweshiek skippering and possibly guide the strategies to recover other Lepidopterans-at-risk. Now with a greater understanding of larval foraging and adult interactions, we may hopefully generate potential causes which explain O. poweshiek’s decline and identify possible solutions to facilitate its successful recovery!

Habitat Suitability Modeling of the Federally Endangered Poweshiek Skipperling in Michigan

The Poweshiek skipperling Oarisma poweshiek (Lepidoptera: Hesperiidae) is a historically common prairie butterfly with a range extending throughout the mesic prairies and prairie fens of the upper Midwestern United States and southern Manitoba, Canada. Rapid, range-wide declines have reduced the number of verified Poweshiek skipperling locations to seven, four of which occur in Michigan. To assist with monitoring and, ultimately, conservation efforts, we developed a habitat model using the software Maxent with ecological and geographical factors. Using a lowest-presence threshold methodology, our habitat suitability model indicated potentially high suitability in 26 of 138 prairie fens with no documentation of Poweshiek skipperling occurrence. The strongest predictors of suitable habitat in our model were prairie fen area and surrounding natural land cover. Wildlife managers can use results from this analysis to expand monitoring to include sites with suitable habitat where Poweshiek skipperling are not currently documented, in addition to identifying potential introduction sites.

Paradoxes of Poweshiek Skipperling (Oarisma poweshiek) (Lepidoptera: Hesperiidae): Abundance Patterns and Management of a Highly Imperiled Prairie Species

Although Oarisma poweshiek sometimes occurred in localized abundance, its known range is centered on the highly decimated northern tallgrass prairie of North America. To aid its conservation, we analyze surveys from 1988 to 1997 of populations no longer being found. While we recorded 2403 individuals at 20 sites, five sites had 87% of individuals, while 12 sites had only 2% of individuals. Most surveys during O. poweshiek flight had zero individuals recorded. In peak vegetative characteristics for O. poweshiek, fire management had the highest mean abundance but the lowest median abundance and lowest percent occurrence compared to idling and haying. Mean abundance was by far the lowest in the first year postfire compared to longer since fire. Median abundance and percent unit surveys where O. poweshiek was found indicated higher abundances the longer since fire. Although this skipper occasionally exhibited super-recoveries after fire, the median result in fire-managed occupied sites was zero. In a few years, abundance appeared synchronized across many sites, either low (1993, 1997) or high (1994-1995). It is only through a constant focus on avoiding the worst-case scenario that the rare best-case scenario of long-term population persistence appears possible for O. poweshiek.