ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01392

ABSTRACT: Across the world, grassland declines over the last century coincide with the declines of many grass feeding butterflies, and the Carson wandering skipper Pseudocopaeodes eunus obscurus (hereafter CWS) is one such taxon. The CWS is a federally endangered subspecies of grass skipper butterfly with only 3 remaining populations on the western edge of the Great Basin Desert, in Nevada and California, USA. Since its federal listing under the Endangered Species Act in 2001 it has been monitored annually, but has not been the subject of intensive research. To improve our understanding of the CWS, we used count data from surveys over the last several decades to assess CWS population status. In addition, to better understand and characterize current habitat for the CWS, we collected vegetation data from 2021–2022 in areas that are currently occupied by the subspecies, and in areas that have no record of CWS occupancy but otherwise met some or all criteria for CWS habitat. We find that the CWS is in decline, and that CWS habitat is characterized by low to moderate densities of saltgrass Distichlis spicata, the larval host, and by the presence of alkaline- or salt-associated nectar resources, as well as other saltgrass community associates. We discuss the possibility that the remaining occupied habitat is not necessarily optimal habitat. We also discuss the implications of our status assessment of the CWS for other butterfly taxa with severely restricted ranges in the arid western USA.