Dakota Skipper(Hesperia dacotae)
by Robert Dana
Official Status: Proposed. Proposed species are those candidate species that were found to warrant listing as either threatened or endangered and were officially proposed as such in a Federal Register notice after the completion of a status review and consideration of other protective conservation measures. Public comment is always sought on a proposal to list species under the ESA. The USFWS generally has one year after a species is proposed for listing under the ESA to make a final determination wheather to list a species as threatened or endangered.
Historical Status: Scientists have recorded Dakota skippers from southern Saskatchewan, across the Dakota’s and Minnesota to Iowa and Illinois.
Current Status: Dakota skippers now occur no further east than western Minnesota and scientists believe the species is no longer present in Illinois and Iowa. Although it likely occurred throughout a relatively unbroken area of grassland in the north-central United States and south-central Canada, it now occurs in scattered remnants of native prairie. Its current distribution straddles the border between tall-grass prairie ecoregions to the east and mixed-grass prairie ecoregions to the west. The most significant remaining populations of Dakota skippers occur in western Minnesota, northeastern South Dakota, and north-central and southeastern North Dakota.
Habitat: Dakota skipper are found in high quality native prairie containing a high diversity of wildflowers and grasses. Habitat includes two prairie types: 1) low (wet) prairie dominated by bluestem grasses, wood lily, harebell, and smooth camas; and 2) upland (dry) prairie dominated by bluestem grasses, needlegrass, pale purple and upright coneflowers and blanketflower.
Life History: Dakota skippers have four basic life stages - egg, larva, pupa, and adult. During the brief adult (flight) period in June and July, female Dakota skippers lay eggs on the underside of leaves approximately 1-2 inches above the ground. These eggs take about 10 days to hatch into larvae. The pale-brown larvae build shelters at or below the ground surface and emerge at night to feed on grass leaves until late summer or early fall when they become dormant. They overwinter as mid-stage larvae in shelters at or just below ground level, typically in the bases of native bunchgrasses. The larvae emerge to continue development the following spring. Pupation takes about 10 days and occurs primarily in June. Males emerge as adults about five days before females. Maximum life span as adults is about three weeks. This brief period is the only time during which Dakota skippers can reproduce.
If they attain maximum longevity of about three weeks and if adequate nectar sources are available, females lay up to about 250 eggs. Nectar provides Dakota skipper with both water and food and is crucial for the survival of both sexes during the flight period. Dakota skippers appear to prefer plants, such as purple coneflowers (Echinacea), whose nectar cannot be obtained by insects without a relatively long, slender feeding tube (proboscis). In the absence of preferred plant species, Dakota skippers attempt to obtain sufficient nectar from less preferred plants.
Aid to Identification: The Dakota skipper is a small butterfly with a 1-inch wingspan. Like other skippers, they have a thick body and a faster and more powerful flight than most butterflies. The upper side of the male’s wings range from tawny-orange to brown with a prominent mark on the forewing; the lower surface is dusty yellow-orange. The upper side of the female’s wing is darker brown with tawny-orange spots and a few white spots on the margin of the forewing; the lower side is gray-brown with a faint white spotband across the middle of the wing. Dakota skipper pupae are reddish-brown and the larvae (caterpillars) are light brown with a black collar and dark brown head.
Reasons for decline: Despite the stewardship of native prairie habitats by public and private landowners, the species faces considerable threats including over-grazing, conversion to cultivated agriculture, inappropriate fire management and herbicide use, woody plant invasion, road construction, gravel mining, invasive plant species, and in some areas, historically high water levels. Although the threats are numerous, opportunities exist to address them and to effectively conserve the species.
Recommendations: Land management that appears to benefit the species includes fall haying, light grazing, sparing and localized use of fire and herbicides, and control of woody plant and exotic species invasion. Preventing further conversion of native prairie habitat should be a priority conservation action.
Comments: Immigration among populations is necessary for the species to persist. The fragmentation of Dakota skipper habitat reduces the exchange of genetic material among populations and may result in a reduced ability to adapt to environmental changes.
Guidelines: Click on link to view Conservation Guidelines (pdf file).