Threatened and Endangered Species - Status Reports
Date Published: October 1999
Number of Pages: 46
Author(s): Ann Potter (WDFW), John Fleckenstein (DNR), Scott Richardson (WDFW), David Hays (WDFW)
The mardon skipper is a small, tawny-orange butterfly currently found at only four, small, geographically disjunct areas in Washington, Oregon, and California. In Washington, nine of 18 historic sites are known to be occupied. Based on several years of repeated survey effort, it has been concluded that populations at five historic sites have been extirpated. Four of these are in south Puget Sound and one is in the southern Cascades. The current status of four other sites is uncertain. Grasslands of the Puget prairies and Washington's southern Cascades are believed to support just a few hundred individuals.
In the Puget lowlands, the mardon skipper is found on glacial outwash prairies where it inhabits open grasslands with abundant Idaho fescue interspersed with early blue violet. In the southern Cascades, the mardon skipper is found in open, fescue grasslands within Ponderosa pine savanna/woodland, at elevations ranging from 1900' to 5100'. South Cascade sites vary in size from small, ½ acre or less meadows, to large grassland complexes, and site conditions range from dry, open ridgetops, to areas associated with wetlands or riparian habitats. Within these southern Cascade and Puget prairie grassland environments, a variety of nectar source plants are important. The short, open stature of native, fescue bunchgrass stands allows mardon skippers to access nectar and oviposition plants.
During the past 150 years, native grasslands have been developed, fragmented, and degraded. Fire historically played an important role in maintaining grassland plant communities. More than 95% of the original prairie grasslands are gone from western Washington. Mardon skippers were likely more widespread and abundant prior to large-scale loss of their open, fescue dominated, grassland habitat.
The grassland and savanna landscapes upon which mardon skippers depend are threatened today by forest encroachment, invasion by native and non-native plants, development, recreational activities, grazing, agricultural practices, and application of herbicides. The butterflies are threatened by insecticides, control practices for invasive plants, military training, fire, and recreational activities.
The extant Washington mardon skipper population consists of a few hundred individuals present at only nine geographically isolated sites, three in Puget Sound and six in the southern Cascades. Many of these sites are under assault from invasive non-native plants, and have human uses which are incompatible with butterfly management. At none of the mardon skipper sites does a mandate and dedicated funding occur for managing the site for mardon skipper habitat.
Due to the mardon skipper's small population size, limited distribution, isolation, and the numerous factors threatening the species and its remaining habitat, the Department believes the species is vulnerable to extirpation and the Puget Sound population in particular, is seriously threatened with extinction. The Department, therefore, recommends the mardon skipper be classified as a State Endangered species.
Potter, A., J. Fleckenstein, S. Richardson, and D. Hays. 1999. Washington state status report for the mardon skipper. Washington Department of Fish and Wildlife, Olympia. 39pp.
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