Assessing the Status and Evaluating Habitat Preferences of the Threatened Skipper, Euphyes vestris harbisoni, in Southern California

Type: dissertation/thesis

Article abstract: The dun skipper is found throughout much of the United States; however, the Harbison’s dun skipper subspecies is geographically isolated in southern California and northern Mexico. It is only known to feed on the San Diego sedge as a larva and a previous listing as a Category 2 species by the United States Fish and Wildlife Service demonstrates concern for its conservation. I conducted surveys in 2021 and 2022 to update the status of populations, and a mark-recapture study in 2022 to estimate population sizes and compare to visual survey estimates. Habitat preferences were explored by collecting habitat covariates in the field and analyzing GIS available environmental data. Skippers were detected at seven of the 17 sites visited in 2021, but due to the small population sizes and low recapture numbers in 2022, population estimates were able to be calculated for only two locations. Habitat analysis found no significant difference found between used and unused portions of woodlands. Woodlands with San Diego sedge were more likely to be historically occupied at higher elevations with warmer summer temperatures. My results show a more restricted distribution of the skipper, and declining populations at extant sites. Small numbers of individuals and low accuracy population estimates indicate that maximum daily counts are a more useful monitoring method for the Harbison’s dun skipper. Habitat analysis determined that the entirety of the woodlands should be considered important habitat, while a large-scale approach highlighted the environmental conditions for areas that may be colonized by the skipper. These data bring into focus areas where conservation and restoration can focus in order to help promote the longevity of the Harbison’s dun skipper.

Number of pages: 57

Authors: Lyons, Abigail;

Month: May

Year: 2023

Keywords: Harbison's dun skipper;

Species: Harbison's Dun Skipper