Adult activities of endangered Oarisma poweshiek butterflies are associated with a soil moisture gradient in tall grass prairie in Manitoba, Canada

Abstract

Endangered in Canada and the United States, the Poweshiek skipperling’s (Oarisma poweshiek (Parker) (Lepidoptera: Hesperiidae)) recovery likely depends on understanding more about its ecology. The characteristics of locations which facilitate various adult activities, such as oviposition and resting, in Manitoba tall grass prairie are unknown. We followed adults in prairie patches to identify locations associated with various behaviours, and subsequently measure vegetative, structural and microclimatic attributes at these microhabitats. Adult skipperlings were observed 34 times resulting in 24 flight tracks and 56 point interactions being recorded. Skipperlings flew almost exclusively in the prairie plant community, with few flights into wetter communities and none in forests. Tracks tended to be tortuous, typical of occupancy in higher-quality habitats. Adult activities appeared to be distributed along a soil moisture gradient: oviposition was associated with the relatively mesic section, resting and/or basking with the drier section, and nectar feeding generally associated with sections throughout the gradient. Adults nectared from a mixture of species during the flight period, consuming nectar from Rudbeckia hirta Linnaeus (Asteraceae) most often. We report previously unknown aspects of O. poweshiek’s ecology.

Implications for conservation: Our findings describe how adult skipperlings might use sections of prairie with different soil moistures to lay eggs, rest, bask and consume nectar. We visualise approaches to ensure all sections are disturbed during stewardship activities and evaluate the degree to which all facilitative soil moistures are present in candidate (re)introduction sites, for the successful recovery of O. poweshiek.