Mardon Skipper Butterfly

Polites mardon

Overview

The Mardon skipper butterfly (Polites mardon) is a small, tawny-orange butterfly dependent upon native, fescue-dominated grasslands in Washington, Oregon, and northwest California. Mardon skippers were likely more widespread and abundant prior to large-scale loss of their open, grassland habitat. This habitat has declined dramatically in the past 150 years due to agricultural and residential development, fire suppression, livestock grazing, and introduction of exotic species. For example, in western Washington, more than 95% of the native prairie grasslands have been destroyed. The butterflies are threatened by insecticides, control practices for invasive plants, military training, fire, recreational activities and facility development. 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. None of the sites are managed for Mardon skipper conservation at this time.

Description

The Mardon skipper (Polites mardon) is in the family Hesperiidae (skippers) and the subfamily Hesperiinae (grass skippers). The Mardon skipper is a small (20-24 mm; <1 inch), tawny-orange butterfly with a stout, hairy body. The upper surface of both wings is orange with broad dark borders. The wings from below are light tan-orange with a distinctive pattern of light yellow to white rectangular spots. Males are smaller than females and have a small, dark brown streak (stigma) on the upper surface of the forewing. Like most members of the Hesperiinae sub-family, Mardon skippers have a fast, skipping flight, bent antennae clubs, and a characteristic basking posture in which the forewings are held at a 45-degree angle and the hind wings are fully spread.

Life History

In the Puget lowlands, the Mardon skipper is found in prairie and meadow habitat with abundant Idaho fescue (Festuca idahoensis). The short, open stature of native, fescue bunchgrass stands allows Mardon skippers to readily access both nectar and oviposition plants. The Mardon skipper larvae feed on Idaho fescue (F. idahoensis) and red fescue (F. rubra). Adult Mardon skippers nectar from the flowers of a variety plants, but blue violet (Viola adunca) is a strongly preferred nectar source and Scotch broom is strongly avoided. Nectaring has also been observed on common vetch (Vicia sativa), prairie lupine (Lupinus sp.), Idaho blue-eyed-grass, penstemon (Penstemon spp.), and wallflower (Erysimum). The Oregon adults avidly visit clover.

Mardon skippers complete one life cycle annually, and in Washington adults emerge from chrysalids between May and July for a month-long flight period. After mating, females deposit their eggs into native bunchgrass where they hatch after 6-7 days. Larvae feed on fescue grass (Festuca spp.) for about three months and the pupae hibernate through the winter and spring.

Distribution

The historic range and abundance of Mardon skippers is not precisely known because systematic and quantitative studies were not conducted prior to 1980. It is clear, however, that the species has suffered significant range contraction and population decline as the grassland habitats with which it is associated have been lost or degraded. For example, Northwest grasslands were formerly much healthier, larger, and interconnected-conditions that would have supported a greater distribution and abundance of Mardon skippers.

Historically, Mardon skippers were collected from three counties in Washington (Thurston, Klickitat, and Yakima), two counties in Oregon (Klamath and Jackson), and Del Norte County, California. The Mardon skipper is now known from 37 sites located in four geographic areas: (1) southern Puget Sound, (2) the Mt. Adams area (eastside of the Cascade Mountains) in southern Washington, (3) the Cascade Mountains in southern Oregon, and (4) Del Norte (north-coastal) California.

Conservation Status

The Mardon skipper has recently been extirpated from four sites in south Puget Sound and one in the southern Washington Cascades and the current status of four other sites in Washington is uncertain. All of the remaining sites are very small, most measuring just a few acres. Most sites support less than 50 butterflies; none support more than a few hundred. The State of Washington Department of Fish and Wildlife (WDFW) lists the Mardon skipper as state endangered and are implementing conservation measures in Washington.

Conservation Needs

Working with landowners

Most of the populations are on Forest Service, BLM or Washington State DNR land. It will be important to work with these agencies to ensure that habitat management takes this butterfly’s protection into account.

Education

Education sheets available at zoological facilities (e.g. zoos, aquariums, botanical gardens with butterflies, butterfly houses, natural history museums) or events at which BFCI partners participate are a valuable way to disseminate information about imperiled butterflies.

When schools and other youth organizations study biodiversity and species extinctions they typically use examples of charismatic megafauna (e.g. bald eagles) or exotic creatures from the tropics. However, vulnerable species found within the state or ecoregion in which students live provide an excellent opportunity to develop curricular materials with a direct link to the students’ home region. In addition to classroom studies, students may be able to visit sites to see the butterflies, as well as talk to the scientists and land managers involved in the species’ conservation.

Educational activities that school students and community members could do include:

  • studying butterfly (insect) life stages;
  • researching the special habitat needs of the Mardon skipper;
  • corresponding or meeting with the biologists managing current Mardon skipper sites;
  • visiting Mardon skipper sites during adult flight season;
  • visiting captive breeding programs;
  • assisting scientists with on-site habitat management;
  • propagating and growing host plants for planting at butterfly sites or use in captive breeding programs; and
  • writing letters to decision makers to ensure that the Mardon skipper receives adequate resources and protection.

Research

WDFW has initiated surveys and research into habitat needs of the Washington populations. There is research into the impact of grazing that has just been initiated in Southern Oregon and surveys are being initiated in California.

Captive Rearing

WDFW has just initiated research into captive rearing.

Recovery Plan

None

More Info

  • U.S. Fish & Wildlife Service: Vince L. Harke. 510 Desmond Drive SE, Suite 102, Lacey, WA 98503-1263. Phone (360) 753-9529. vince_harke@fws.gov
  • Arcata Fish and Wildlife Office: Robin Hamlin. (707) 822-7201. robin_hamlin@fws.gov
  • Klamath Falls Fish and Wildlife Office: Ron Larson (541) 885-8481. ron_larson@fws.gov
  • WA Dept of Fish and Wildlife: Ann Potter, Wildlife Biologist. 600 Capitol Way N, Olympia, WA 98501-1091. (360) 902-2496. potteaep@dfw.wa.gov
  • The Xerces Society: Scott Hoffman Black, Executive director. 4828 SE Hawthorne Blvd., Portland, OR 97215. Phone (503) 534-2706. sblack@xerces.org

References

  • Barry J. W. 1993. Predicting and Measuring Drift ofBacillus thuringensis Sprays. Environmental Toxicology and Chemistry, Vol 12, pp. 1977-1989
  • Crawford, R. C., and H. Hall. 1997. Changes in the south Puget prairie landscape. Pages 11-16 in P. V. Dunn and K. Ewing, editors. Ecology and Conservation of the South Puget Sound Prairie Landscape. The Nature Conservancy, Seattle, Washington. 289 pp.
  • Fleckenstein, J. and A. Potter 1999. 1997, 1998 Project summary: Puget prairie butterfly surveys. Wa. Dept. of Nat. Res. Olympia. Unpublished Report, 21 May 1999. 14 pp.
  • Mattoon, S. O., J. F. Emmel, and T. C. Emmel. 1998. The distribution of Polites mardon (Lepidoptera: Hesperiidae) in North America, and description of a new subspecies from southern Oregon. Pages 767-774 in T. C. Emmel, editor. Systematics of western North American butterflies. Mariposa Press, Gainesville, Florida. 878 pp.
  • Potter A. and J. Fleckenstein. 2001. Southern Cascade Surveys for the Mardon Skipper, Summary Year 2000. Washington Department of Fish and Wildlife, Olympia. 11 pp.
  • 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. 39 pp.
  • Pyle R. M. 2002. The Butterflies of Cascadia. Seattle Audubon Society.
  • Runquist E. 1999. Butterfly Community Surveys in the Soda Mountain Region, Jackson County, Oregon. Bureau of Land Management, Medford, OR. 27 pp.
  • USFWS Mardon Skipper page

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