1. ECOS
2. Species Profile for Pawnee Montane skipper (Hesperia leonardus montana)

Pawnee Montane skipper (Hesperia leonardus montana)

Listing Status:   

Where Listed: WHEREVER FOUND

General Information

The skipper, a member of the Hesperidae butterfly family, was first described in 1911 as Pamphila (Hesperia) pawnee montana. In 1982, two species (Hesperia pawnee and Hesperia leonardus) were combined, retaining the specific name leonardus, and treating the Pawnee montane skipper as Hesperia leonardus montana. The subspecies occurs only in the South Platte Canyon River drainage system in Colorado, in portions of Jefferson, Douglas, Teller, and Park Counties. The Pawnee montane skipper is a small, brownish-yellow butterfly with a wing span slightly over 1 inch. Small, fulvous (dull brownish-yellow), usually distinct spots occur near the outer margins of the upper surface of the wings, while one to four distinct brownish to off-white spots occur on the lower (ventral) surface of the wings. The ventral spots are larger on the hind wing and are generally whiter on the female butterfly.

• States/US Territories in which the Pawnee Montane skipper, Wherever found is known to or is believed to occur:  Colorado
• US Counties in which the Pawnee Montane skipper, Wherever found is known to or is believed to occur:  View All

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» Life History

Habitat Requirements

Skippers occur in dry, open, ponderosa pine woodlands on moderately steep slopes with soils derived from Pikes Peak granite. The understory is very sparse in the pine woodlands. Blue grama grass, the larval food plant, and prairie gayfeather, the primary nectar plant, are two necessary components of the groundcover strata. Small clumps of blue grama occur throughout the hot, open slopes inhabited by skippers. Prairie gayfeather occurs throughout the ponderosa pine woodlands. Skippers are very uncommon in pine woodlands with a tall shrub understory or where young conifers dominate the understory. A quantitative estimate of optimum skipper habitat characteristics includes: tree canopy cover of 30 percent with ponderosa pine cover of 25 percent and Douglas-fir of 5 percent; tree density of less than 120 trees/acre in the smallest size class (0-5 inches diameter breast high) and overall tree density of less than 200 trees/acre; shrub and grass cover generally less than 10 percent; prairie gayfeather flowering stem density ranging from 50 to 500 flowering stems/acre; and blue grama canopy cover of 1 to 5 percent. The limiting habitat endpoints for the skipper seem to be treeless areas of 5 acres or more at one extreme to woodlands with understory shrub cover of 25 percent or more at the other extreme. The skipper is largely absent from steep, north-facing Douglas-fir stands where neither prairie gayfeather nor blue grama are plentiful. Prairie gayfeather seems to require openings from single event disturbance such as logging or fire-created habitat, but does not tolerate continuous disturbance. However, it appears that the skipper does not colonize such areas for at least several years after disturbance and regeneration. Burnt or logged areas surveyed in 1986 had low numbers of skippers.

Food Habits

Although prairie gayfeather is the most important nectar source for the species, other plants have also been noted as nectar sources. The musk thistle (Carduus nutans) is important along river bottoms and up some ravines. Female skippers have been observed in large numbers on musk thistle along the South Platte River canyon bottom.

Movement / Home Range

The skipper has a restricted range, occupying an area (though not necessarily all the available habitat within it) roughly 23 miles long and 5 miles wide. It occurs along the mainstem of the South Platte River for approximately 20 miles and the North Fork of the South Platte River for approximately 15 miles upstream from their confluence with Cheesman Reservoir and Crossons, respectively. Currently, the skipper’s habitat forms one continuous band along the North and South Forks of the South Platte River and includes two of their tributaries, Buffalo and Horse creeks, respectively. This type of habitat configuration allows for an interchange of individuals throughout the habitat. The plant community preferred by the skipper is the northern-most extension of the ponderosa pine/blue grama grass habitat type documented from southern Colorado and northern New Mexico. However, the preferred nectar plant of the skipper, prairie gayfeather does not occur in similar habitats to the south. The northeastern limits of the ponderosa pine/blue grama grass community overlapping with the southwestern limit of the prairie gayfeather may contribute to the maintenance of the species in this limited area. The elevational range of the species is 6,000 to 7,500 feet. Studies in 1985 showed that the ratio of males to female skippers was much greater at higher elevations than at lower elevations (32 males/7 females above 7,100 feet and 34 males/20 females below 7,100 feet).

Reproductive Strategy

Pawnee montane skippers emerge as adult butterflies as early as late July. Males emerge before females by an average of a week to 10 days. The adults spend most of their short existence feeding and mating. Adult females directly deposit eggs singly on leaves of blue grama grass (Bouteloua gracilis), the larval food plant. The species overwinters as larvae, and little is known of the larval and pupal stages. Pupation is generally short (13-23 days), as in most butterflies. The species completes its life cycle (egg to larva to pupa to adult butterfly to egg) annually. Adults probably fly until a major killing frost occurs. Additionally, the phenology of prairie gayfeather (Liatris punctata), the primary nectar plant, and the presence of the skipper are highly synchronous.

Other

There are two other subspecies of this group: Hesperia leonardus leonardus occurs in the eastern United States and Canada, and Hesperia leonardus pawnee occurs on the Northern Great Plains. The presence of ventral hind wing spots and its darker color differentiates Hesperia leonardus montana from Hesperia leonardus pawnee. Since modern settlement of Colorado, the Platte River Canyon has experienced a number of habitat changes that likely have resulted in loss, modification, and curtailment of former skipper habitat and range. Habitat loss likely has occurred as a result of fire suppression over the last 120 years. The encroachment of conifers and the subsequent loss of grasses and prairie gayfeather have reduced the quality and quantity of skipper habitat. Causes of lost habitat include Cheesman Reservoir, catastrophic fire, residential development, roads, and planted and mowed pastures. Invasion of noxious weeds, such as knapweed, which may outcompete blue grama and prairie gayfeather are also a serious threat to the skipper.

» Other Resources

NatureServe Explorer Species Reports -- NatureServe Explorer is a source for authoritative conservation information on more than 50,000 plants, animals and ecological communtities of the U.S and Canada. NatureServe Explorer provides in-depth information on rare and endangered species, but includes common plants and animals too. NatureServe Explorer is a product of NatureServe in collaboration with the Natural Heritage Network.

ITIS Reports -- ITIS (the Integrated Taxonomic Information System) is a source for authoritative taxonomic information on plants, animals, fungi, and microbes of North America and the world.

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