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Hesperia leonardus Montana, Pawnee Montane Skipper

  • Hesperia leonardus Montana: about 3.2 - 4.5 cm wingspan. This species is brownish-yellow with white spots on the outer margins of its wings. It was first described in 1883 by David Bruce. He found them in abundance in the town of Salida, Colorado. They were then shipped to leading lepidopterist W.H. Edwards of West Virginia. The skippers were then, like the rest of W.H. Edwards collection, shipped to the Carnegie Museum of Natural History in Pittsburg, PA.

    This butterfly is native to only one area of the Colorado Front Range. Its habitat is southwest of Denver, where the South Platte River drainage meets up with its north fork. It tends to inhabit dry, open Ponderosa Pine woodland with sparse groundcover at 6,000-7,500 feet. As of right now, it only has 37.9 square miles to call its home as noted by the Denver Water Department. This species’ roaming area was bigger in the 60’s and 70’s, but with the advancement of housing developments and the expansion of Denver’s boundaries, the skipper has lost its range and some of its food sources.

    The skipper has two main plants that it feeds on. The larvae feed on Blue Grama grass (Bouteloua gracilis) and the adults get their nectar from Prairie Gayfeather or Prairie Blazing Star (Liatris pycnostachya). The adults have been spotted on Musk Thistle, but it is not their primary food source. Both plants are native to the front range of Colorado as well as most of the Midwest.

    On September 25, 1987, the Pawnee Montane Skipper was listed on the Federal Endangered Species List as a “threatened” species. The reason for this listing was caused by habitat loss over the last 120 years of fire suppression as well as the growth of conifers and loss of grasslands containing their feeding plants. In 1990, the proposed construction of the Two Forks Dam and Reservoir was not approved by the EPA, because of the immediate threat that would impose on the skipper’s habitat. If the construction of the dam had happened, 22% of the skipper’s habitat would be lost, which would cause a 23-42% loss in population.

    In June of 2002, the Hayman Wildfires charred 138,000 acres of land. This resulted in a 40% decrease in the skipper’s habitat. Two previous fires in 1996 and 2000, Buffalo Creek and Hi Meadow, wiped out an additional 10% of skipper habitat. In 1987, Denver Water Department conducted a survey of the Pawnee Montane Skipper population and it was estimated that there was 116,000. Because of the loss of land and feeding plants, the population is estimated to be at least 50-60% less than the previous survey in 1987, but no official survey has been conducted since then.

    The recovery plan for the Pawnee Montane Skipper was placed into effect on September 2, 1998. The recovery plan includes monitoring its habitat and removal of less than 5% loss of skipper’s habitat to developments such as roads, housing, or recreational. A heavy planting project of the Blue Grama Grass and Prairie Blazing Star (density of 150 or more flowering stems/acre) is planned for. Along with the planting of feeding plants, the project is also aimed at eradicating noxious weeds like Mullen, Knapweed, Russian and Canadian Thistle, Hound’s tongue, or any other noxious plant that will compete with the skipper’s nutrient plants. The recovery plan is set to end in 2010 and the total cost for the plan is $330,000.


Written by: Tim Wells

Image credit: NA