United States Department of Agriculture

Biological Assessment of Oil and Gas 

Development on the Little Missouri National 

Grassland

Jack L. Butler, Jacqueline P. Ott, Cynthia R. Hartway,

and Brian E. Dickerson

Rocky Mountain

Research Station

General Technical Report

RMRS-GTR-384

Forest November 2018

Service
Butler, Jack L.; Ott, Jacqueline P.; Hartway, Cynthia R.; Dickerson, Brian E. 2018. 

Biological assessment of oil and gas development on the Little Missouri 

National Grassland. Gen. Tech. Rep. RMRS-GTR-384. Fort Collins, CO: U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Research Station. 67 p.

Abstract

The Little Missouri National Grassland is the largest designated National Grassland 

in the United States and represents one of the best examples of intact native mixedgrass prairie in the United States. The Little Missouri National Grasslands occurs 

entirely within the Williston Basin, which has been a leading source of conventional 

oil and gas production since the 1950s. Recent advances in horizontal drilling and 

hydraulic fracturing (since 2000) have greatly increased energy extraction activities on 

the Little Missouri National Grassland. The objective of this assessment is to synthesize existing knowledge from peer-reviewed literature and administrative studies that 

describe the actual and potential impacts of oil and gas development on the biological 

resources of the Little Missouri National Grassland. The assessment focuses on how 

energy extraction activities may impact soils, vegetation, and wildlife, with specific reference to threatened and endangered species.

Keywords: grassland, North Dakota, assessment, oil, gas, energy development, soils, 

vegetation, threatened and endangered species

Cover photos: Little Missouri National Grassland (top); oil and gas development on the Little Missouri 

National Grassland (bottom) (photos by Jason Dekker, USDA Forest Service).
Authors

Jack L. Butler, Research Ecologist (retired), USDA Forest Service Rocky Mountain 

Research Station, Rapid City, South Dakota.

Jacqueline P. Ott, Research Ecologist, USDA Forest Service Rocky Mountain 

Research Station, Rapid City, South Dakota.

Cynthia R. Hartway, Research Associate, South Dakota State University.

Brian E. Dickerson, Wildlife Biologist, USDA Forest Service Rocky Mountain 

Research Station, Rapid City, South Dakota.

Acknowledgments

We thank Deborah Finch for developing the proposal that initiated the project and 

her active support and encouragement throughout the publication process. We gratefully acknowledge the financial support of the Rocky Mountain Region and the Rocky 

Mountain Research Station of the U.S. Department of Agriculture, Forest Service. 

Bill O’Donnell, John Kinney, and Karen Dunlap of the Dakota Prairie provided helpful guidance that is much appreciated. Meghan Dinkins, Dakota Prairie, and Brice 

Hanberry, Rocky Mountain Research Station, reviewed early drafts of the paper and 

provided many helpful suggestions that greatly improved the manuscript. We thank 

David Hawksworth for his valuable assistance in formatting and helping to edit the final 

product.

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Contents

SECTION 1: INTRODUCTION ..........................................................................1

SECTION 2: OVERVIEW OF OIL AND GAS DEVELOPMENT ........................3

Background of Oil and Gas Development on

Little Missouri National Grassland....................................................3

Projected Biological Effects During Oil and Gas Development.................4

Oil Exploration: Seismic Surveys, Drilling, and Infrastructure 

Establishment Including Road and Pipeline Construction .............4

Oil Extraction: Fracturing, Pumping, and Additional

Infrastructure Establishment ..........................................................5

Oil Distribution: Transportation by Truck, Rail, and Pipelines ..............5

SECTION 3: SPECIFIC IMPACTS RESULTING FROM OIL AND GAS 

DEVELOPMENT....................................................................................6

Soil and Vegetation ...................................................................................6

Disturbance and Alteration in Aboveground Vegetation and

Soil Characteristics ........................................................................6

Summary .............................................................................................8

Particulate Matter ......................................................................................8

Summary ...........................................................................................10

Wildlife.....................................................................................................11

Introduction........................................................................................11

Habitat Loss and Fragmentation........................................................11

Direct Mortality...................................................................................13

Alterations of Behavior.......................................................................14

Aquatic Communities.........................................................................15

Water Withdrawal ........................................................................15

Increased Sedimentation.............................................................16

Specific Studies Pertinent to Little Missouri National Grassland.............16

Songbirds...........................................................................................17

Songbirds Summary ....................................................................23

Grouse...............................................................................................23

Ungulates...........................................................................................25

Ungulates—Pronghorn (Antilocarpa americana).........................25

Ungulates—Rocky Mountain Elk (Cervus elaphus).....................26

Ungulates—Mule Deer (Odocoileus hemionus) ..........................26

Aquatic Communities.........................................................................28

SECTION 4: THREATENED AND ENDANGERED SPECIES .......................29

Dakota Skipper (Hesperia dacotae) ........................................................29

Introduction........................................................................................29

General Habitat Characteristics of Dakota Skipper ...........................30

Habitat Characteristics in Relation to Reproduction

and Foraging................................................................................32

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Threats and Management of Dakota Skipper Habitat........................34

Dakota Skipper Critical Habitat on the Little Missouri

National Grassland ......................................................................39

Summary ...........................................................................................45

Sprague’s Pipit (Anthus spragueii)..........................................................46

Introduction........................................................................................46

Habitat and Diet Characteristics of Sprague’s Pipit

(Anthus spragueii)........................................................................46

Threats and Management of Sprague’s Pipit Habitat ........................48

Summary ...........................................................................................50

Northern Long-Eared Bat (Myotis septentrionalis) ..................................50

Introduction and North Dakota Status................................................50

Threats and Management of Northern Long-Eared

Bat Habitat (Myotis septentrioalis)...............................................51

Summary ...........................................................................................53

SECTION 5: ONGOING RESEARCH IN NORTH DAKOTA /

OTHER RESOURCES ........................................................................55

U.S. Geological Survey (USGS)..............................................................55

U.S. Department of Agriculture–Agriculture

Research Station (ARS) .................................................................55

North Dakota State University.................................................................55

LITERATURE CITED .......................................................................................56

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USDA Forest Service RMRS-GTR-384. 2018. 1

SECTION 1: INTRODUCTION

The Little Missouri National Grassland (LMNG) in western North Dakota, at 

418,150 ha (1,033,271 acres), is the largest designated National Grassland in the 

United States. The semi-arid continental climate of the LMNG is seasonal with cold, 

dry winters and warm, wet summers. January and July temperatures are on average 

15 °F and 69 °F, respectively. Annual precipitation normals (i.e., 30-year averages) 

across the grassland are typically between 14.5 and 15.5 in. Approximately 50 percent 

of the rainfall occurs between May and July (NOAA Regional Climate Center 2017). 

However, inter-annual precipitation is highly variable and can range from 10 to 25 

inches (36.8 and 39.4 cm). Due to high inter- and intra- annual precipitation variability, 

moisture deficits can occur during critical growing periods. Snowfall averages 53 

inches (135 cm) each winter and can produce large snow drifts in draws.

The landscape is characterized by rolling mixed-grass prairie, buttes, and badlands. 

Plateaus and terraces were historically cut by the Little Missouri River and its tributaries as the river was diverted during glaciation events. Erosion is common in the 

badlands as evidenced by the lack of vegetation on many slopes and the occurrence 

of large slumps. Soils outside of the badlands are quite stable and readily support 

herbaceous and woody vegetation. Three Major Land Resource Areas (MLRA) defined 

by the National Resource Conservation Service (2017) occur within the LMNG: (1) 

MLRA 54- Rolling Soft Shale Plain, (2) MLRA 58C- Northern Rolling High Plains, 

northeastern part (majority of LMNG), and (3) MLRA 58D-Northern Rolling High 

Plains, eastern part (small portion of LMNG).

Vegetation includes grasslands dominated by cool-season (C3) perennial grasses 

and grass-likes such as western wheatgrass (Pascopyrum smithii), needle-and-thread 

(Hesperostipa comata), prairie Junegrass (Koeleria macrantha), and threadleaf sedge 

(Carex filifolia) with upland areas of warm-season (C4) perennial grasses such as blue 

grama (Bouteloua gracilis) and little bluestem (Schizachyrium scoparium). Hardwood 

draws occur along upland draws and depressions and contain green ash (Fraxinus 

pennsylvanica), buffaloberry (Shepherdia spp.), and chokecherry (Prunus virginiana). 

Cottonwood forests dominate the riparian areas along the Little Missouri River. Stands 

of Rocky Mountain juniper (Juniperus scopulorum) occur on moderate-to-steep northand east-facing slopes. Multiple species of sage and cedar can occur in rocklands and 

breaks. Major wildlife species include elk, mule deer, white-tailed deer, pronghorn 

antelope, bighorn sheep, coyote, mountain lion, red fox, black-tailed prairie dog, jackrabbit, sharp-tailed grouse, sage-grouse, ferruginous hawk, and golden eagle.

The LMNG occurs entirely within the Williston Basin, which is a large area of accumulated sediments that cover about 250,000 km2 in western North Dakota, eastern 

Montana, northwestern South Dakota, and southern Saskatchewan (Bluemle 1980). 

The basin is experiencing rapid land cover changes related to recent (since 2000) oil 

and gas development (Preston and Kim 2016). The aim of this assessment is to identify 

and synthesize the best available science on potential impacts of oil and gas developmental activities on the biological resources of the LMNG, especially vegetation and 
2 USDA Forest Service RMRS-GTR-384. 2018.

wildlife. This assessment was designed to (1) provide scientific information to help 

inform management on current and potential impacts, (2) provide a ready reference for 

experienced as well as new managers on the LMNG, and (3) foster lines of communication between scientists and managers that will facilitate rapid integration of ongoing 

research results into the management decisionmaking process.
USDA Forest Service RMRS-GTR-384. 2018. 3

SECTION 2: OVERVIEW OF OIL AND GAS 

DEVELOPMENT

Background of Oil and Gas Development on

Little Missouri National Grassland

Oil development and production occurred primarily on the Elm Coulee oil field 

in eastern Montana starting in 2000 before shifting to western North Dakota in 2007 

after the Parshall Oil Field discovery (Nordeng 2010). Oil production from the Bakken 

and Three Forks formations in western North Dakota started accelerating in 2006 and 

has increased by almost 9x as of August 2015 (Energy of North Dakota 2015). The 

exploration phase during 2006–2012 enabled oil producers to establish producing 

wells in order to meet the requirements of each lease. Now, the area is entering the 

harvest phase when producers will drill additional wells at each well pad and focus on 

maintaining pumping units. Wells are expected to produce for about 30–45 years before 

being sealed and the land reclaimed (Energy of North Dakota 2017; Miskimins 2009 in 

Parish et al. 2013).

After the mineral rights are leased and any necessary surface use agreements are 

established with the landowner, a well pad is developed over several months on 4–10 

acres of land (Energy of North Dakota 2017). Topsoil is removed and stockpiled for 

future reclamation of the site. Appropriate measures (e.g., liners, berms) to protect 

the surrounding land and groundwater are put into place and then drilling begins. 

Hydraulic fracturing, also known as fracking, is commonly used to increase well production so that oil may flow more freely out of the fractured reservoir rock. After the 

pumping unit is installed, the well pad size is often reduced by 25 percent. Brine water 

produced during fracking and oil production is typically reinjected deep into a lower 

saline rock formation at a licensed disposal site (Gleason and Tangen 2014; Energy of 

North Dakota 2017). The number of wells drilled on a pad determines the size of the 

pad. With current horizontal drilling technology, more than 14 wells may be located on 

one pad.

At the local scale, wells were historically (pre-2000) placed at higher densities (~1 

per 40 acres) because they were limited by the belowground area they could reach. 

With the recent advances in horizontal drilling, well pad density has lowered due to 

strategic placement of well pads because one well pad can host multiple wells that 

produce oil from 640 (1 sq. mile) or 1,280 acres (2 sq. miles). With planning, well pad 

locations can be located along predetermined parallel lines, creating corridors of energy 

development with up to 4 miles of undisturbed land surface between corridors. 

At the regional scale, well pad density is driven by the timing of oil and gas discoveries, the cost of oil and gas production, and leasing terms. In 1986–1995, new wells 

in the Williston Basin were mainly located around the intersection of Billings, Golden 

Valley, and McKenzie Counties. However, new well development from 2006–2010 

occurred in other areas along and to the east of the Nesson anticline (the eastern portion 

of Williams and McKenzie Counties and in the heart of Mountrail and Dunn Counties; 
4 USDA Forest Service RMRS-GTR-384. 2018.

Nordeng 2010). Since 2014, permits to place wells near areas of interest, including specific waterways, State and National Parks, and buttes, are subject to additional review 

according to the North Dakota Industrial Commission PP 2.01-2.04 (NDIC 2017).

Harvested oil and gas is transported out of the region by truck, rail, and pipeline. 

Typically, oil is hauled short distances from the well by truck and then loaded onto 

rail or pipeline to be transported to refineries outside the region. Smaller “gathering” 

pipelines feed into larger regional transmission lines. Currently, pipeline infrastructure 

is unable to meet the demand for oil and gas export from North Dakota. Excess oil is 

transported mostly by rail (Kringstad 2016). Natural gas can only be safely transported 

by pipeline and excess undergoes combustion onsite (i.e., flaring).

Projected Biological Effects During Oil and Gas Development

Environmental resources can be affected in multiple ways along the oil and gas 

development and production timeline. Based on larger synthesis studies (Brittingham 

et al. 2014; Northrup and Wittemyer 2013; Parish et al. 2013 and citations therein), the 

following general environmental effects at or near the soil surface may occur during oil 

and gas exploration, extraction, and distribution. Some effects may be similar among 

the three stages.

Oil Exploration: Seismic Surveys, Drilling, and Infrastructure 

Establishment Including Road and Pipeline Construction

Vegetation/Habitat/Wildlife

•  Soil damage through compaction and or mixing of soil horizons

•  Loss of natural vegetation, either direct or indirect

•  Disturbance and/or loss of ecologically sensitive areas including wetlands

•  Introduction of new species (beneficial, pest, or invasive)

•  Functional habitat loss, habitat fragmentation, and habitat avoidance

•  Reduction in population densities of amphibians, birds, and mammals

•  Alteration of predator-prey relationships

•  Increased access to formerly remote areas for hunting (or poaching) and use of off-road 

vehicles

Water Resources

•  Air and groundwater contamination from disposal of drill cuttings

•  Generation of radioactively contaminated waste streams such as process water, drilling 

fluids (i.e., “mud”), and equipment

•  Damage to aquatic systems from increased sediment or changes to drainage patterns

•  Terrestrial surface water contamination from oil spills and sedimentation
USDA Forest Service RMRS-GTR-384. 2018. 5

Oil Extraction: Fracturing, Pumping, and Additional Infrastructure 

Establishment

Vegetation/Habitat/Wildlife

•  Loss of natural vegetation including invasion by non-native plant species

•  Plant and soil toxicity due to brine spills

•  Fires from terrestrial oil spills

•  Air pollution from flaring/light pollution

•  Habitat fragmentation, leading to altered animal behavior, movement, and home ranges 

including avoidance of oil and gas infrastructure

•  Reduction in population densities of amphibians, birds, and mammals due to impacts 

(e.g., acoustic masking, direct mortality such as collision and bird mortality due to exposure to produced water, increased stress, increased hunting pressure) on all stages of their 

life cycles (i.e., reproduction, juvenile, and adult)

•  Shift in community composition to generalist species with declines in habitat specialists

Water Resources

•  Alteration of groundwater flow and quality

•  Alteration of river flow

•  Generation/spilling of fracturing fluid and produced water containing toxic and radioactive materials

Oil Distribution: Transportation by Truck, Rail, and Pipelines

•  Introduction and dispersal of non-native plant species

•  Inhibition of plant growth by road dust and chemicals used in road maintenance

•  Biological effects of spills

•  Increased mortality of wildlife due to vehicle collisions

•  Loss of migratory routes
6 USDA Forest Service RMRS-GTR-384. 2018.

SECTION 3: SPECIFIC IMPACTS RESULTING FROM 

OIL AND GAS DEVELOPMENT

Soil and Vegetation

Disturbance and Alteration in Aboveground Vegetation and Soil 

Characteristics

Intact grassland communities are continually undergoing natural small-scale disturbances, such as slumps created by large precipitation events in erosion-prone badlands 

topography or mounds created by ants, pocket gophers, or other mammals that form 

solitary dens. Small-scale soil disturbances are usually revegetated from the soil seed 

bank or from neighboring plants either via seed or by clonal expansion (Rogers and 

Hartnett 2001). Some large-scale disturbances, such as fire, only disturb the aboveground vegetation and leave the soil relatively undisturbed except for nutrient additions 

from ash and soil warming due to reduced vegetation cover. Grassland vegetation 

is generally very resilient and quickly recovers following fire as most belowground 

organs of perennial plants survive the disturbance and are able to resprout (Benson and 

Hartnett 2006).

However, vegetation recovery following large-scale disturbances that destroy the 

belowground bud bank through soil movement depends on the surrounding undisturbed 

community to meet the demand for propagules to fully revegetate the area. Oftentimes 

the seed rain from the surrounding undisturbed community or the residual soil seed 

bank does not provide enough propagules of the desired species to quickly revegetate 

large areas. In grasslands, seed banks typically do not reflect the current plant community composition but instead primarily consist of species that can readily colonize 

disturbed habitat (Fair et al. 1999). Therefore, restoration efforts of severe large-scale 

disturbances are heavily influenced by additional seeding of desired species (Viall et al. 

2014). Disturbances and subsequent restoration practices also provide opportunities for 

invasive species to establish viable populations (Preston 2015).

Oil and gas development increases the extent and frequency of large-scale, severe 

disturbances because it requires construction of oil well pads, roads, and pipelines. 

Infrastructure development removes the entire surface vegetation and mixes the upper 

soil layers. Therefore, restoration efforts are often required at two separate occasions: 

(1) when infrastructure construction is complete and its construction footprint is reduced to its operating footprint and (2) when infrastructure is completely removed at 

the completion of oil extraction. Recovery of vegetation is strongly influenced by the 

supply of propagules (i.e., seeds or buds) and the soil.

As soil is moved around during infrastructure construction supporting energy extraction, soil horizons that developed over centuries or millennia are disrupted, net primary 

production is reduced, and nutrient cycling processes are altered, which collectively 

initiates an almost instantaneous loss of soil organic matter (Larney and Angers 2012). 

Each soil horizon maintains a different composition of ions and nutrients and as these 

horizons are mixed during construction, the soil profile loses much of its natural 
USDA Forest Service RMRS-GTR-384. 2018. 7

structure and function. Both abiotic and biotic shifts occur within the soil as particle 

size may be altered and fungal and bacteria communities, habituated to a stable medium, are now disrupted and translocated.

The cumulative effects of these soil disturbances can be quite substantial and persist 

for long periods of time. Rowell and Florence (1993) examined a variety of grassland 

soil characteristics in south-central Alberta that had been disturbed by energy extraction 

activities and compared those characteristics to undisturbed grasslands. They reported 

that disturbed grasslands had higher electro-conductivity and sulfate concentrations and 

lower pH, organic matter, cation exchange capacity, and moisture content compared 

to undisturbed sites. Similar results were reported by Nasen et al. (2011) for soils in 

a grassland ecosystem in Saskatchewan impacted by oil and gas development. These 

researchers also reported that disturbed sites had significantly lower thickness and litter of the Ah soil horizon, which is an upper soil horizon that originates from organic 

matter enrichment. The cumulative effects of the disturbances on soil properties were 

manifested in lower herbaceous ground cover and diversity on disturbed sites compared to undisturbed sites. Many of the disturbance impacts reported by Nasen et al. 

(2011) extended beyond the physical footprint of the disturbance and persisted for more 

than 50 years, which the authors largely attributed to poor mitigation and reclamation 

practices on abandoned wellsites during a time of limited monitoring.

A somewhat similar legacy effect of disturbances was reported by Viall et al. (2014) 

on oil roads on the LMNG that were discontinued and reclaimed. These researchers 

collected information on soil and plant community characteristics on roads that were 

reclaimed at three time periods (age 1 = 1983–1987, age 2 = 1988–1994, and age 3 = 

1995–2002). They also compared soil characteristics between the center of the road 

and 50 m from the center of the road in native prairie. They found that time since reclamation did not affect the soil and plant characteristics they measured, indicating that 

after 30 years post-reclamation the composition of the soil microbial community and 

plant community had not reached the same ecological condition as the adjacent prairie. 

In addition, Viall et al. (2014) reported significant differences in soils and vegetation 

between the on-road samples compared to the prairie samples after 30 years postreclamation. Viall et al. (2014) attributed the failure of reclaiming roads to conditions 

resembling the native prairie to reduced soil organic matter that was not able to support 

soil microbial populations at an adequate level. Naeth et al. (1987) also found reduced 

soil organic matter and increased salts on grasslands sites in Alberta that were disturbed 

by installation of natural gas pipelines. The reduced soil organic matter adversely 

affected soil chemistry, which, in turn, hampered the soil’s ability to replenish soil 

organic matter through net primary production. The authors indicated that it would take 

about 50 years for natural processes to restore half of the organic matter that was lost 

during pipeline installation.

Because soil organic matter plays such a key role in the physical, chemical, and 

biological properties of soils, current wellsite reclamation efforts almost always include the use of organic amendments (Zvomuya et al. 2007; Larney et al. 2012). The 

application of the appropriate organic amendment (organic material with low carbon: 

nitrogen ratios) has a very positive effect on soil biological activity for both faunal 
8 USDA Forest Service RMRS-GTR-384. 2018.

and microbial communities (see review by Larney and Angers 2012). However, the 

increased resource availability following application of organic amendments may 

increase the potential for invasive plants, which may have become established during energy development construction (Preston 2015), to rapidly expand. Seastedt and 

Pyšek (2011) provide a summary of the processes involved with plant invasions into 

grassland ecosystems and found increased resource availability to be the most common factor determining community level invasibility (also see Stohlgren et al. 1999). 

Consequently, while organic amendments can greatly enhance reclamation efforts in 

native prairie ecosystems, monitoring and controlling invasive plants may be necessary. 

Hammermeister et al. (2003) reported that soils with higher soil nitrogen favored plant 

species with high colonization rates and rapid growth, which were native wheatgrasses 

in this study, but invasive plants are also characterized by rapid colonization and 

growth. 

Summary

Infrastructure construction for energy extraction increases the extent and frequency 

of large-scale, severe disturbances. During construction, surface vegetation is removed, 

soil horizons are disrupted, soil organic matter is reduced, and soil microbial communities are altered. The general effects of the disturbances on vegetation and soils is 

usually manifested in lower herbaceous ground cover and diversity that may persist 

for relatively long periods of time unless restoration practices are initiated. Because 

soil organic matter plays such a major role in the physical, chemical, and biological 

characteristics of soils, wellsite reclamation almost always includes the use of organic 

amendments, which has a very positive effect on soil biological activity that greatly 

enhances reclamation efforts. However, enhancing soil resources through the use of 

organic amendments may increase the risk of colonization and expansion of invasive 

plants.

Particulate Matter

Atmospheric particulate matter (PM) is a solid heterogeneous material that is of 

natural and anthropogenic origin that directly impacts the health and survival of all 

living organisms (Rai 2016). Atmospheric PM has the potential to adversely impact 

a wide variety of structural and functional characteristics at multiple spatial scales of 

biological organization (table 3.1), which may have the more long-term environmental 

effect of reducing biodiversity and ecosystem services (Grantz et al. 2003). While it 

is relatively easy to generalize about potential impacts of PM, it is difficult to identify 

specific threats related to energy development in the Bakken Region because of a lack 

of information regarding specific PM constituents.

Probably the most visible source of PM in the Bakken in western North Dakota is 

dust from road traffic. Roads are a common feature on all but the most isolated landscapes. The construction, maintenance, and use of roads over the past half century have 

directly and indirectly modified a wide variety of aquatic and terrestrial ecosystems in 

numerous ways (see reviews by Forman and Alexander 1998; Spellerberg 1998; and 
USDA Forest Service RMRS-GTR-384. 2018. 9

Trombulak and Frissell 2000). The environmental and ecological impact of roads can 

extend well beyond their physical footprint.

The recent increase in heavy truck traffic on unpaved roads associated with the rapidly expanding oil and gas extraction activities in the Bakken Region of western North 

Dakota has generated concern about the potential impact of road dust emissions on soil 

and vegetation resources (Creuzer et al. 2016). Preston and Kim (2016) estimated that 

construction of well pads in the Williston Basin from 2000 to 2015 directly converted 

approximately 12,990 ha of land to energy development with an additional 12,121 ha 

disturbed, some of which was reclaimed. Approximately 2,300 drilling-related truck 

trips are required for every well that is drilled and hydraulically fractured (Tolliver 

2014, as reported in Creuzer et al. 2016).

Although roads are a common source of dust, the specific effects of road dust on 

plant populations and communities has received little attention. Overall impacts of road 

dust on plants may include altered rates of photosynthesis, respiration, and transpiration that may lead to decreased productivity in some species depending on their morphology and physiology. Arctic bryophyte and lichen communities as a group appear 

to be among the most adversely impacted by road dust particles because they absorb 

water and nutrients directly from the atmosphere. Farmer (1993) highlights the damaging effects of dust (primarily from cement factories) on the physiological activity of a 

wide variety of crop plants. Information on the effects of road dust on native plants is 

sparse, especially for North American prairies (but see Nasen et al. 2011).

Matsuki et al. (2016) evaluated the potential impact of dust generated from energy 

extraction activities in a semi-arid grassland in Western Australia. Although specific 

Level of Biological Organization Structural Property Functional Property

Organism Leaf area Photosynthesis

Root and shoot morphology Respiration

Individual biomass Nutrient acquisition from soil

Allometry Nutrient leaching from foliage

Age distribution Carbon allocation 

Individual mortality

Population Size distribution Competitive vigor

Population density, distribution, and 

dispersion

Reproductive success

Biomass productivity 

Genetic diversity Redundancy and resilience

Species diversity

Community Balance of trophic levels Succession

Canopy leaf area index Soil stabilization

Root distribution Productivity

Biomass

Ecosystem Element pool sizes Nutrient and water cycling

Soil type Energy flux

Table 3.1. Structural and functional properties of vegetated systems potentially impacted by atmospheric particulate 

matter (Copied from Grantz et al. 2003).
10 USDA Forest Service RMRS-GTR-384. 2018.

patterns were variable, they reported that deposition of dust could be relatively high 

within 150 m of the source but decreased rapidly with increasing distance from the 

source. Their results failed to detect significant negative impacts on plant health and 

survivorship and concluded that variation in growing conditions, specifically precipitation, had more of an impact than dust. They attributed the lack of a detectable effect 

of dust to several factors. One, a certain amount of dust is usually present in arid and 

semi-arid environments because of wind erosion; consequently, plants in arid and semiarid environments evolved with a certain amount of dust generated naturally by wind 

erosion. Second, the naturally occurring deposition of dust is a short-term impact that 

generally occurs during the dry season when plants have reduced photosynthesis, thus 

making the effects of dust difficult to detect. The authors concluded that dust generated 

from energy extraction activities is similarly short term.

Creuzer et al. (2016) evaluated the effects of increased road dust related to energy 

development in the Bakken Region on wetlands. They found significantly higher levels 

of dust loading 10 m from the road in the study area influenced by energy development compared to an area without energy development. However, dust loads decreased 

dramatically with increasing distance from the road where a 46 percent decrease in dust 

can occur when greater than 40 m from the road. Despite the reported high levels of 

dust reported by Creuzer et al. (2016), they found that road dust had a minor effect on 

water quality and wetland soils.

The general conclusion from the sparse information that is available is that loading of road dust can be substantial adjacent to roads. Creuzer et al. (2016) reported 

an annual deposition of 647 g/m2 of dust within 10 m of the road. Such high levels of 

deposition likely have the potential to adversely impact the physiological processes of 

plants, as evidenced from studies on individual crop plants (dust from cement production, Farmer 1993) and arctic bryophytes and lichens (Walker and Everett 1987). Siteand species-specific research on plants adjacent to roads with high truck traffic would 

provide valuable insight into long-term population and community level trends related 

to heavy dust loading. Because roads often serve as conduits for exotic plants, road 

dust may play a role in mediating competitive interactions among native and exotic 

species, although this has not been studied. Additionally, high deposition of dust along 

roads could reduce the availability of host plants for Dakota skipper larvae and nectar 

sources of adult butterflies, further reducing and fragmenting the habitat for the Dakota 

skipper in western North Dakota, but more research is needed. 

Summary

Natural and anthropogenic produced atmospheric PM has the potential to adversely 

impact a wide variety of organisms at multiple spatial and temporal scales. Road dust 

may be the most conspicuous source of PM in the Bakken Region of western North 

Dakota. Road dust has the capacity to alter several physiological processes of plants 

that have the potential to reduce productivity and diversity. Several studies show that 

while accumulation of road dust on plants may be heavy near the road, it is often 

considered to be a short-term phenomenon that decreases substantially with increasing 

distance from the road. A study of road dust related to energy extraction activities that 
USDA Forest Service RMRS-GTR-384. 2018. 11

Disturbance

Individual Behavior

Survival

Reproduction

Population

growth rate

Population

abundance

is specific to the Bakken Region indicated that road dust had a minor effect on water 

quality and wetland soils. However, the high dust loads immediately adjacent to roads 

can be quite substantial, which could adversely affect plant communities adjacent to 

the road. This could be especially important in areas of critical habitat for the Dakota 

skipper on the LMNG, but more research is needed.

Wildlife

Introduction

The infrastructure, by-products, and human activities associated with oil and gas 

development can affect the occurrence and abundance of terrestrial and aquatic animal 

species through multiple overlapping, direct and indirect pathways (fig. 3.1). Major 

impacts to wildlife communities include: the loss, fragmentation, and degradation 

of habitat; direct mortality of individuals; and alterations to individual behavior that 

ultimately affect the survival, reproductive output, or abundance of animals (reviewed 

by Jones et al. 2015; Northrup and Wittemyer 2013). Major impacts to aquatic communities include: spills and leaks of contaminants into surface and ground waters; 

altered hydrology due to water withdrawals; and increased sedimentation into waterways resulting from land clearing and road building (reviewed by Entrekin et al. 2011; 

Souther et al. 2014). We first give a general overview of each of these potential impacts 

followed by an in-depth summary of studies directly linking the development of oil and 

gas infrastructure and extraction activities to the abundance, survival, and reproductive 

rates of species known to occur in the LMNG.

Habitat Loss and Fragmentation

The quantity and quality of habitat directly determines the number of individuals 

that an area can support. Consequently, the loss and degradation of habitat is the leading cause of species extinction worldwide (Pimm and Raven 2000; Sala et al. 2000; 

Wilcove et al. 1998). As habitat is lost or degraded, remaining resources can support 

fewer individuals, meaning population abundance must decline and populations may 

become locally extirpated.

Figure 3.1—Potential effects of oil and gas development on wildlife populations. Disturbance can have direct 

effects on the survival and reproduction of wildlife populations or indirect effects on these population parameters via alterations in behavior. 
12 USDA Forest Service RMRS-GTR-384. 2018.

As habitat is lost or degraded in oil and gas fields by the construction of well pads, 

access roads, and associated infrastructure, the remaining habitat becomes increasingly 

fragmented (i.e., divided into smaller more isolated patches; see Fahrig 2003 for a comprehensive review). Habitat fragmentation can affect the ability of individuals to move 

about the landscape and acquire necessary resources. By creating barriers to movement, 

or blocking or impeding the ability to access critical areas for foraging or reproduction, 

the reduction and fragmentation of habitat can reduce reproductive opportunities and 

increase the time required to acquire resources. For example, many ungulate species 

migrate between seasonal ranges, and the habitat quality of these ranges and the ability 

to freely move between them for access can play a critical role in their population viability (O’Gara and Yoakum 2004; Riley et al. 2012; Toweill and Thomas 2002).

As the degree of isolation of habitat fragments increases, the connectivity between 

habitat fragments—and populations living within those fragments—decreases. When 

movement between fragments is strongly restricted, habitat fragmentation can lead to 

population isolation and, in the long term, to the eventual loss of genetic diversity via 

genetic drift (e.g., in red squirrels: Bakker and Van Vuren 2004; in grand skinks: Berry 

et al. 2005; in desert bighorn sheep: Epps et al. 2005). The loss of genetic diversity due 

to population isolation can eventually lead to inbreeding depression and reduced fitness 

in individuals (reviewed by Hedrick and Kalinowski 2000).

Fragmentation also increases edge effects (Fahrig 2003), which can enable the 

spread of invasive species into remaining habitats (e.g., feral cats, brown-headed cowbirds), increase the abundance of certain predator species, and alter the composition of 

predator communities. The abundance of mesopredators (such as foxes, skunks, and 

raccoons) have been shown to increase in edge habitats and fragmented landscapes 

(Dijak and Thompson 2000; Winter et al. 2000). Such species can be important nest 

predators in grassland communities and can strongly impact the reproductive success 

and survival of grassland birds. In a study of grassland birds in prairie habitat fragments throughout the Great Plains and Midwestern States of the United States, Herkert 

et al. (2003) analyzed nest predation rates in prairie fragments that ranged in size from 

less than 100 ha to greater than 1,000 ha. They found that nest predation rates increased 

as the size of habitat fragments decreased, with 78–84 percent of nests failing due to 

predation in small (<100 ha) prairie fragments, in contrast to 54–68 percent of nests 

failing in large (>1,000 ha) prairie fragments.

One form of habitat degradation that has gained increasing attention in recent 

years is noise pollution. Drilling, natural gas compressor stations, construction, and 

transportation activities can all be sources of intense noise, and research has increasingly demonstrated negative consequences of this noise across a wide range of species 

(reviewed by Barber et al. 2010). Anthropogenic noise can be detrimental to wildlife 

by interfering with acoustical signals required for foraging (Schaub et al. 2008), reproduction (Habib et al. 2007), and survival (Halfwerk et al. 2011; Rabin et al. 2006) and 

by increasing stress and vigilance levels. Species that use acoustical cues for foraging 

may be particularly affected. For example, gleaning bats—a guild that includes the 

northern long-eared bat—locate and capture their prey using sounds and cues generated 

by prey movements. A study by Schaub et al. (2008) comparing foraging activities of 
USDA Forest Service RMRS-GTR-384. 2018. 13

the greater mouse-eared bat (Myotis myotis) in noisy versus quiet environments found 

that the bats spent significantly less time foraging in noisy environments. The foraging 

success (percent of prey captured) of bats in noisy environments was also significantly 

lower than in quiet environments. Conversely, a predator’s inability to locate prey 

using auditory cues, or their avoidance of noisy areas altogether, may have positive effects on the occurrence and abundance of their prey species (Francis et al. 2011).

Direct Mortality

Activities and infrastructure associated with oil and gas extraction can directly increase mortality rates in animals in multiple ways. These include: collisions with vehicles on access roads; collisions with fences or power lines; mortality due to gas flares, 

contamination, and poisoning in reserve pits and evaporation ponds; and increased 

predation rates and human harvest associated with roads, trails, and anthropogenic 

infrastructure.

Mortality due to vehicle collisions can have substantial effects on the demography 

and abundance of animal populations (reviewed by Beebee 2013; Trombulak and 

Frissell 2000). Vehicle collisions kill an estimated 1 million vertebrates per day in 

the United States (Forman and Alexander 1998). Numbers of invertebrates killed in 

vehicle collisions is likely much higher, with the number of pollinators killed annually 

by vehicles estimated to be in the billions (Baxter-Gilbert et al. 2015). Mortality due 

to vehicle collisions can have significant impacts on the long-term viability of small 

populations. For example, in Florida, before mitigation efforts were enacted to reduce 

road mortality, vehicle collisions killed approximately 10 percent of the endangered 

Florida panther population (Felis concolor coryi) and 16 percent of the endangered 

Key deer population (Odocoileus virginianus clavium) (Forman and Alexander 1998).

Life history characteristics can make some species particularly vulnerable to vehicle 

collisions. Amphibians and reptiles are especially vulnerable to road mortality due to 

their relatively inconspicuous nature, slow movements, limited behavioral responses, 

and seasonal movements to and from breeding and hibernation grounds (Beebee 2013; 

Trombulak and Frissell 2000). Both amphibian and reptile populations are declining 

worldwide (Böhm et al. 2013; Stuart et al. 2004), and for both, the proliferation of 

roads is considered to be a major threat. Indeed, road mortality has been implicated as 

a determining factor in the endangerment or decline of some populations of reptiles 

(snakes: Row et al. 2007; Rouse et al. 2011; turtles: Gibbs and Shriver 2002; Marchand 

and Litvaitis 2004) and amphibians (Gibbs and Shriver 2005).

The species most at risk by a particular road will depend on the width of the road, 

traffic levels, vehicle speeds, and the proximity of the road to critical habitat or movement corridors (reviewed by Forman and Alexander 1998; Rytwinski and Fahrig 2012). 

For example, amphibians and reptiles tend to be particularly susceptible on two-lane 

roads with low to moderate traffic; large and mid-sized mammals are especially susceptible on two-lane, high-speed roads; and birds and small mammals experience their 

highest vehicle collision rates on wider, high-speed highways. Roads built near wetlands or riparian areas are a particular danger and can have significant negative impacts 
14 USDA Forest Service RMRS-GTR-384. 2018.

on animal abundance. On one such road in Ontario Canada, Ashley and Robinson 

(1996) report that over 625 snakes and 1,700 frogs were killed annually per kilometer 

of road.

Collisions with human infrastructure such as fences, power lines, and buildings have 

also been shown to be a significant source of mortality in some species. The taxa most 

affected by collisions with anthropogenic infrastructure are birds (Loss 2016). During 

flight, take off, swooping in on prey, or attempting to land, birds may collide with 

buildings, communications towers, fences, or transmission lines (Manville 2005). In 

the United States, annual estimates of bird mortality due to power line collisions alone 

range from hundreds of thousands to over 100 million birds killed (Erickson et al. 

2005). While almost all bird species can be vulnerable to collisions (Rioux et al. 2013), 

large bodied species with low maneuverability (e.g., grouse, waterfowl, cranes) or species with narrow visual fields are typically most at risk for fatal collisions with power 

lines and fences (Barrientos et al. 2012). Large mammals such as ungulates can also 

be vulnerable to mortal wounding or death as a result of fence collision (e.g., see Paige 

2012).

In addition to the risk of collision, anthropogenic infrastructure can negatively 

impact animal populations by increasing predation risk. The presence of transmission 

lines and fences has been shown to increase predation rates on breeding and nesting 

sage-grouse by increasing the number of perches available to raptors (Aldridge and 

Boyce 2007; Fletcher et al. 2003; Slater and Smith 2010). Hethcoat and Chalfoun 

(2015) found that songbirds nesting in proximity to gas wells were more likely to have 

their nests predated by small mammals, and postulated that the infrastructure around 

wells were providing refugia for these nest predators.

Alterations of Behavior

Human activity and infrastructure can also negatively affect the abundance, survival, 

or reproduction of species by altering the behavior of those species. Behavioral alterations due to human disturbance that can ultimately affect the demography or abundance 

of species include avoidance behavior, increased vigilance behavior, or decreased 

activity levels.

Many animal species avoid areas with human disturbance or infrastructure due to a 

heightened perception of risk associated with increased human activity, noise, traffic, 

or even the physical presence of the infrastructure itself. Such avoidance behavior constitutes a functional loss of habitat; the necessary resources may still be available and 

of high quality, but avoidance behavior makes the habitat unavailable to the individuals 

or species affected. While the effects of the direct loss and conversion of habitat can be 

relatively easy to assess, the consequences of habitat loss due to avoidance behaviors 

can be considerably more difficult to quantify (e.g., Sawyer et al. 2006) as the signal of 

altered behavioral patterns may take many years to manifest as demographic impacts.

One common form of habitat loss due to the altered behavior of wildlife is the 

avoidance of roads and traffic. In a meta-analysis of abundance data from 234 bird and 

mammal species, Benítez-López et al. (2010) analyzed the mean difference in animal 
USDA Forest Service RMRS-GTR-384. 2018. 15

abundance at varying distances from roads. They found that, overall, the relative 

abundance of both birds and mammals was significantly reduced in the presence of 

roads. On average, bird species avoided habitats within approximately 1 km of roads, 

while mammal species avoided habitats within approximately 5 km of roads. Overall, 

this avoidance behavior led to a decline in species abundance of birds and mammals 

of 28–36 percent and 25–38 percent within 2.6 km and 17 km of road infrastructure, 

respectively.

Human presence and activity may cause some species to increase defense or 

vigilance behaviors (Stankowich 2008; Stankowich and Blumstein 2005) resulting in 

a decrease in the amount of time devoted to foraging, resting, or other activities that 

increase fitness. The result can be poorer body condition, reduced survival, or reduced 

reproductive success (the number of surviving offspring per individual), which in turn 

can lead to a decrease in the overall population growth rate and abundance (Bechet et 

al. 2004; Ciuti et al. 2012; Creel et al. 2007; Fortrin et al. 2004; Zannette et al. 2011). 

For example, Phillips and Alldridge (2000) conducted a control-treatment study in 

which humans repeatedly approached female elk (Cervus canadensis) on calving 

grounds, causing them to get up and run, while elk on control calving grounds were left 

undisturbed. Phillips and Alldridge estimated the proportion of surviving calves across 

calving grounds and found that the proportion surviving was significantly lower in the 

disturbed populations compared to the undisturbed controls.

Aquatic Communities

The primary impacts of oil and gas development on aquatic communities are spills 

and leaks of contaminants into surface and ground waters; altered hydrology due to water withdrawals; and increased sedimentation into waterways resulting from land clearing and road building (reviewed by Entrekin et al. 2011; Souther et al. 2014). To date, 

relatively few studies have explicitly addressed how oil and gas development influence 

the quality and function of stream ecosystems. However, any development that alters 

the quality or quantity of surface and ground waters has the potential to negatively 

impact aquatic communities (Davis et al. 2006).

The strength of the impacts of oil and gas development on aquatic communities 

will depend on the particular environmental conditions of those communities. Slope, 

geology, soil type, precipitation levels and vegetation all contribute to the vulnerability of aquatic communities to surface level disturbances (Entrekin et al. 2015). In a 

comprehensive assessment of stream catchment conditions across shale plays in North 

America, Entrekin et al. (2015) found that the low annual precipitation, highly erosive 

soils and relatively high density of streams and wetlands within the Bakken play are 

likely to make these catchments especially vulnerable to stressors associated with oil 

and gas development.

Water Withdrawal

Drilling of unconventional oil and gas wells can require up to 7 million gallons of 

water per well (Entrekin et al. 2011), and surface waters typically serve as the source 

for these waters. In practice, several wells may be drilled per well pad and these 
16 USDA Forest Service RMRS-GTR-384. 2018.

wells may be in use for decades. Such intensive levels of water withdrawal within a 

relatively small area has the potential to vastly alter the water level and flow rates of 

nearby streams.

In the western Great Plains, negative effects of water withdrawals on aquatic communities could be exacerbated because stream systems are already prone towards 

intermittent flooding and drying (Davis et al. 2006; Dodds et al. 2004). Reduced 

water levels and flow rates in streams are associated with warmer water temperatures, 

increased concentrations of pollutants, and less dissolved oxygen (Souther et al. 2014), 

all of which can affect the structure and functioning of aquatic communities. In streams 

prone to drying, fish populations may persist through extreme conditions by seeking 

refuge in isolated springs and pools (Bramblett and Zale 2000; Labbe and Fausch 

2000). Any reduction in groundwater levels due to water withdrawals has the potential 

to further reduce flows in streams that are spring-fed or directly connected to groundwater, resulting in the loss of these important refugia habitats (Davis et al. 2006; Falke 

et al. 2010).

Increased Sedimentation

Land clearing and construction activities associated with oil and gas development 

(e.g., construction of well pads, compressor stations, roads and pipelines) have the 

potential to alter surface environments and thereby increase sedimentation into local 

streams. The effects of sedimentation on aquatic communities have been extensively 

studied, and have been shown to alter the survival, behavior, abundance, diversity, and 

community structure of both aquatic and semi-aquatic species (e.g., Allan 2014 2014; 

Eaglin and Hubert 1993; Henley et al. 2010; Kemp et al. 2011; Wood and Armitage 

1997).

One particular danger to Great Plains streams may be the loss of coarse or gravel 

substrates in streams due to accumulations of fine sediment—for example, silt, clay, 

and fine organic and inorganic matter. Many fish species require coarse substrates for 

spawning and the accumulation of fine sediments can negatively affect the suitability 

of these sites, reducing reproductive opportunities (Eaglin 1993; Henley et al. 2010; 

Wood and Armitage 1997). In Great Plains streams, coarse substrates are relatively rare 

(Davis et al. 2006) yet provide important spawning habitat for species such as goldeye 

(Hiodon alosoides), sturgeon chub (Macrhybopsis gelida), longnose dace (Rhinichthys 

cataractae), and sand shiner (Notropis stramineus) (Bramblett et al. 2005). For those 

species that do successfully spawn, high levels of sediment can endanger their offspring. In freshwater systems, high levels of fine sediments can suffocate and kill fish 

during the egg stage (Burkhead and Jelks 2001; Sutherland 2005) and reduce growth 

rates (Sutherland 2005; Sutherland and Meyer 2007).

Specific Studies Pertinent to Little Missouri National Grassland

Despite the diversity of ways that oil and gas development can potentially affect 

species—and the diversity of species that may be affected—the majority of studies on 

the impacts of oil and gas development in North American grasslands and shrub lands 
USDA Forest Service RMRS-GTR-384. 2018. 17

have focused on just three groups: songbirds, grouse, and ungulates, while the majority 

of wildlife impacts studied fell into two categories: changes in mortality rates (e.g., 

nest survival) and changes in abundance due to avoidance behavior. We summarize 

these studies individually below, focusing only on those species known to occur on the 

LMNG.

Songbirds

Results of studies on the effect of oil and gas development on songbird abundance 

and nest success are summarized in tables 3.2 to 3.4. A detailed summary of the methods and results from each individual study follow below.

Ingelfinger and Anderson (2004) studied the effect of gas field access roads on the 

relative density of three species of sagebrush obligate songbirds (Brewer’s sparrows 

[Spizella breweri], sage sparrows [Amphispiza belli], and sage thrashers [Oreoscoptes 

montanus]) and two non-obligate species (horned larks [Eremophila alpestris] and 

vesper sparrows [Pooecetes gramineus]) within the Jonah II and Pinedale Anticline 

Project Area of western Wyoming. They conducted point counts at variable distances 

(0–600 m) from the edges of four roads, each of which experienced relatively low 

traffic volumes (10–700 vehicles per day). On average, the density of the sagebrush 

obligates was reduced by 39–60 percent within a 100-m buffer around all roads, with 

negative impacts to abundance greatest along access roads with higher traffic volumes.

Linnen (2008) studied the effect of oil extraction infrastructure on bird abundance 

in southeastern Alberta, Canada. In this 1-year study, Linnen surveyed the abundance 

of territorial males of multiple bird species at increasing distances from oil wells and 

associated access roads (oil wells and roads were combined in the analysis, i.e., type of 

disturbance was not differentiated). Species studied included: vesper sparrows, Baird's 

sparrow (Ammodramus bairdii), chestnut-collared longspur (Calcarius ornatus), 

Sprague's pipit (Anthus spragueii), McCown’s longspur (Rhynchophanes mccownii), 

savannah sparrow (Passerculus sandwichensis), and horned larks. Results indicate that 

chestnut-collared longspur, Sprague's pipit, and Baird's sparrow were significantly less 

abundant in areas near oil wells and access roads (within 100 m, 300 m and 400 m, 

respectively) than in areas >400 m away from the wells and roads. Abundance of 

McCown’s longspur declined with increasing proximity to wells and roads, but the 

decline was not statistically significant. Vesper sparrows were significantly more abundant near wells and roads (within areas <50 m away). Savannah sparrows and horned 

larks showed no pattern in abundance with relation to oil wells or access roads.

In a 2-year study in Alberta, Canada, Hamilton et al. (2011) investigated the effect of well density and landscape features on the occurrence and abundance of three 

songbird species (savannah sparrow, chestnut-collared longspur, and Sprague’s pipit). 

The two levels of well densities investigated were: nine wells/2.59 km2 (N = 5) and 16 

wells/2.59 km2 (N = 3). Statistical models to estimate occurrence and abundance included: soil type, elevation, and topography, along with well density and anthropogenic 

disturbance to natural vegetation, (i.e., the combined areas affected by wells, pipelines, 

trails, and roads). Model results indicated that the occurrence of Sprague’s pipit was 

negatively related to increased well density, the occurrence and abundance of savannah 
18 USDA Forest Service RMRS-GTR-384. 2018.

Table 3.2

—Summary of study results on the effect of proximity to, or increased density of, well pads and compressor stations on the abundance or density of 

songbirds. “Habitat” is habitat in which study took place (grassland or sagebrush steppe). “Endemic” is whether the species is endemic to that habitat. 

“Negative,” “Positive,” and “No effect” denote the effect of the covariates on the abundance or density each species; numbers are the number of studies 

reporting each result.

Covariate Habitat Endemic Species Negative No effect Positive Referencea

Proximity to 

oil or gas 

infrastructure

Grassland Yes Ammodramus bairdii (Baird's sparrow) 3 1 B, F, H, IGrassland Yes Anthus spragueii (Sprague's pipit) 2 1b B, H, IGrassland Yes Calcarius ornatus (Chestnut-collared longspur) 2 B, IGrassland Yes Rhynchophanes mccownii (McCown's longspur) 1c BGrassland No Ammodramus leconteii (LeConte's sparrow) 1 EGrassland No Ammodramus savannarum (Grasshopper sparrow) 1 1 E, IGrassland No Anthus rubescens (American Pipit) 1 EGrassland No Cistothorus platensis (Sedge wren) 1 EGrassland No Dolichonyx oryzivorus (Bobolink) 1 IGrassland No Eremophila alpestris (Horned lark) 1 1 B, FGrassland No Molothrus ater (Brown-headed cowbird) 1 1 H, IGrassland No Passerculus sandwichensis (Savannah sparrow) 2 2 1 B, C, E, H, 

I

Grassland No Pooecetes gramineus (Vesper sparrow) 1 1 B, HGrassland No Setophaga coronate (Yellow-rumped warbler) 1 EGrassland No Spizella pallid (Clay-colored sparrow) 1 IGrassland No Sturnella neglecta (Western Meadowlark) 3 E, H, IGrassland Yes Ammodramus bairdii (Baird's sparrow) 1 F

Density of oil 

or gas wells

Grassland Yes Anthus spragueii (Sprague's pipit) 1 1b D, FGrassland Yes Calcarius ornatus (Chestnut-collared longspur) 1 1 D, FGrassland No Eremophila alpestris (Horned lark) 1 FGrassland No Passerculus sandwichensis (Savannah sparrow) 2 D, FGrassland No Pooecetes gramineus (Vesper sparrow) 1 FGrassland No Sturnella neglecta (Western Meadowlark) 1 F

Sagebrush Yes Amphispiza belli (Sage sparrow) 1c CSagebrush Yes Oreoscoptes montanus (Sage thrasher) 1 CSagebrush Yes Spizella breweri (Brewer's sparrow) 1 CSagebrush No Eremophila alpestris (Horned lark) 1 CSagebrush No Pooecetes gramineus (Vesper sparrow) 1 C a References cited are: (A) Ingelfinger and Anderson 2004; (B) Linnen 2008; (C) Gilbert and Chalfoun 2011; (D) Hamilton et al. 2011; (E) Lawson et al. 2011; 

(F) Gaudet 2013; (G) Hethcoat and Chalfoun 2015; (H) Ludlow et al. 2015; and (I) Thompson et al. 2015. b Percent vegetation cover was most important driver of abundance, not proximity to wells. c Trend is not statistically significant.
USDA Forest Service RMRS-GTR-384. 2018. 19 Table 3.3—Summary of study results on the effect of oil and gas access roads and trails on the abundance or density of songbirds. “Habitat” is habitat in which study took place (grassland or sagebrush steppe). “Endemic” is whether the species is endemic to that habitat. “Negative,” “Positive,” and “No effect” denote the effect of the covariates on the abundance or density each species; numbers are the number of studies reporting each result. a References cited are: (A) Ingelfinger and Anderson 2004; (B) Linnen 2008; (C) Gilbert and Chalfoun 2011; (D) Hamilton et al. 2011; (E) Lawson et al. 2011; (F) Gaudet 2013; (G) Hethcoat and Chalfoun 2015; (H) Ludlow et al. 2015; and (I) Thompson et al. 2015. Covariate Habitat Endemic Species Negative No effect Positive Referencea Proximity to access road or trail Grassland Yes Ammodramus bairdii (Baird's sparrow) 2 1 B, H Grassland Yes Anthus spragueii (Sprague's pipit) 2 1 B, H Grassland Yes Calcarius ornatus (Chestnut-collared longspur) 1 1 B, I Grassland Yes Rhynchophanes mccownii (McCown's longspur) 1 B Grassland No Ammodramus leconteii (LeConte's sparrow) 1 E Grassland No Ammodramus savannarum (Grasshopper sparrow) 1 1 E, I Grassland No Anthus rubescens (American Pipit) 1 E Grassland No Cistothorus platensis (Sedge wren) 1 E Grassland No Dolichonyx oryzivorus (Bobolink) 1 I Grassland No Eremophila alpestris (Horned lark) 1 B Grassland No Molothrus ater (Brown-headed cowbird) 2 H, I Grassland No Passerculus sandwichensis (Savannah sparrow) 2 2 B, E, H, I Grassland No Pooecetes gramineus (Vesper sparrow) 1 2 B, H Grassland No Setophaga coronate (Yellow-rumped warbler) 1 E Grassland No Spizella pallid (Clay-colored sparrow) 1 I Grassland No Sturnella neglecta (Western Meadowlark) 2 1 E, H Sagebrush Yes Amphispiza belli (Sage sparrow) 1 A Sagebrush Yes Oreoscoptes montanus (Sage thrasher) 1 A Sagebrush Yes Spizella breweri (Brewers sparrow) 1 A Sagebrush No Eremophila alpestris (Horned lark) 1 A Sagebrush No Pooecetes gramineus (Vesper sparrow) 1 A
20 USDA Forest Service RMRS-GTR-384. 2018. Table 3.4—Summary of study results on the association of oil and gas related covariates on the reproductive success of songbirds (nest survival, number of fledglings). Covariates are: proximity to oil and gas infrastructure; proximity to access roads and trails; gas or oil well density; and percent of habitat destroyed by oil or gas infrastructure. “Habitat” is habitat in which study took place (grassland or sagebrush steppe). “Endemic” is whether the species is endemic to that habitat. “Negative,” “Positive,” and “No effect” denote the effect of the covariates on the abundance or density each species; numbers are the number of studies reporting each result. Covariate Habitat Endemic Species Negative No effect Positive Referencea Proximity to oil or gas infrastructure Grassland Yes Ammodramus bairdii (Baird's sparrow) 1 F Grassland Yes Calcarius ornatus (Chestnut-collared longspur 1 F Grassland No Passerculus sandwichensis (Savannah sparrow) 1 1 F, H Grassland No Pooecetes gramineus (Vesper sparrow) 1 F Grassland No Sturnella neglecta (Western Meadowlark) 1 F Proximity to access roads or trails Grassland Yes Ammodramus bairdii (Baird's sparrow) 1 1 F, H Grassland Yes Anthus spragueii (Sprague's pipit) 1 1 F, H Grassland Yes Calcarius ornatus (Chestnut-collared longspur 1 F No Eremophila alpestris (Horned lark) 1b F Grassland No Passerculus sandwichensis (Savannah sparrow) 1 F Grassland No Pooecetes gramineus (Vesper sparrow) 1 1 F, H Grassland No Sturnella neglecta (Western Meadowlark) 1 1 F, H Density of oil or gas wells Sagebrush Yes Artemisiospiza nevadensis (Sagebrush sparrow) 1 G Sagebrush Yes Oreoscoptes montanus (Sage thrasher) 1 G Sagebrush Yes Spizella breweri (Brewer's sparrow) 1 G % Habitat loss due to oil or gas infrastructure Sagebrush Yes Artemisiospiza nevadensis (Sagebrush sparrow) 1 G Sagebrush Yes Oreoscoptes montanus (Sage thrasher) 1 G Sagebrush Yes Spizella breweri (Brewer's sparrow) 1 G a References cited are: (A) Ingelfinger and Anderson 2004;(B) Linnen 2008; (C) Gilbert and Chalfoun 2011; (D) Hamilton et al. 2011; (E) Lawson et al. 2011; (F) Gaudet 2013; (G) Hethcoat and Chalfoun 2015; (H) Ludlow et al. 2015; and (I) Thompson et al. 2015. b Trend is not statistically significant.
USDA Forest Service RMRS-GTR-384. 2018. 21

sparrows were higher in areas with high well densities compared with low well densities, and the abundance and occurrence of chestnut-collared longspurs was not related 

to well density.

Gilbert and Chalfoun (2011) studied the effect of well pad density on the abundance 

of five species of sagebrush-steppe songbirds in the Jonah-Pinedale Anticline Project 

Area natural gas fields and the Big Piney-La Barge oil fields of western Wyoming. 

They compared the abundance of five species over 2 years on sites with differing well 

densities (0 wells/km2, 1–6 wells/km2, 7–15 wells/km2, and >15 wells/km2). Results indicated a statistically significant decline in the abundance of vesper sparrows, Brewer’s 

sparrows, and a non-significant decline in sage sparrows with increasing well density 

per site, while horned larks abundance increased and sage thrasher abundance showed 

no association with increasing well densities.

In a study of the effect of energy infrastructure on the abundance of grassland birds 

in the oil fields of San Padre Island in Texas, Lawson et al. (2011) investigated mean 

abundance of several bird species along linear transects emanating outward from active oil wells, inactive oil wells, and access roads. The bird species studied included 

seven that occur in North Dakota: western meadowlark (Sturnella neglecta), savannah 

sparrow, grasshopper sparrow (Ammodramus savannarum), sedge wren (Cistothorus 

platensis), Le Conte’s sparrow (Ammodramus leconteii), American pipit (Anthus 

rubescens), and yellow-rumped warbler (Setophaga coronata). Their results indicated 

no significant trend in bird abundance with increasing proximity to either active or 

inactive wells (range: 30 to 300 m from wells), but they did find a significant decrease 

in abundance with increasing proximity to access roads, suggesting that all studied species avoided areas near roads.

In 2010 and 2011, Gaudet (2013) monitored 392 nests of seven species of grassland 

songbirds in southwestern Saskatchewan, Canada, to determine the effects of plot-level 

disturbance and proximity to gas compressor stations on their density and reproductive success. Species studied included: chestnut-collared longspur, vesper sparrow, 

Sprague’s pipit, savannah sparrow, Baird’s sparrow, horned lark, and western meadowlark. Results indicated that the effect of gas wells and related infrastructure (compressor stations, trails, and fences) on songbird density and reproductive success varied by 

species and by type of disturbance. Plots with a higher percentage of land converted to 

gas drilling and related infrastructure (“high disturbance” plots) supported relatively 

higher densities of vesper and savannah sparrows than “low disturbance” plots, but 

lower densities of chestnut-collared longspur and horned lark. Increased proximity to 

compressor stations was associated with lower densities of Baird’s and savannah sparrows and higher densities of horned larks. The density of Sprague’s pipit and western 

meadowlark was best explained by vegetation structure. In particular, Sprague’s pipit 

density increased with increased exotic vegetation cover. Gaudet postulates that this is 

most likely because the structure of the exotic vegetation fit their preference for tall, 

dense vegetation (Davis 2005).

Nest surveys indicated that the nest survival of vesper, Baird’s, and savannah sparrows decreased with increased proximity to wells, fences, and trails, while western 
22 USDA Forest Service RMRS-GTR-384. 2018.

meadowlark nest survival increased with increased proximity to access trails. No nests 

of Sprague’s pipit were found within 100 m of compressor stations or wells, and no 

horned lark nests were found within 100 m of wells.

In a follow-up to the Gilbert and Chalfoun (2011) study, Hethcoat and Chalfoun 

(2015) examined the effect of well densities on the nest survival of Brewer’s sparrows, 

sagebrush sparrow (Artemisiospiza nevadensis), and sage thrasher. They also looked 

at the effect of a measure of habitat loss on nest survival, which they quantified as the 

proportion of area around each nest (a 1 km2 area) that contained sagebrush habitat. 

They found no overall pattern between nest survival and well pad density, but found 

nest survival decreased as the proportion of sagebrush habitat around nests decreased. 

They found that the formation and distribution of well pads had a greater effect on the 

amount of sage brush habitat lost, and thus nest survival, than the density of well pads 

alone.

In a 2-year study in the Antelope Creek Habitat Development Area in southeastern 

Alberta, Canada, Ludlow et al. (2015) studied the density and nest survival of five 

grassland bird species and a brood parasite in plots that varied in both the distance to 

infrastructure associated with energy development (oil and gas wells, access roads, and 

trails) and in the percent cover of crested wheatgrass (Agropyron cristatum), an exotic 

weed that often becomes established following anthropogenic disturbance. Species 

studied were: savannah sparrow, Baird’s sparrow, western meadowlark, Sprague’s pipit, 

vesper sparrow, and the brown-headed cowbird (Molothrus ater). Bird density, nest 

placement, and nest survival were modeled as functions of proximity to wells, roads, 

access trails, vegetation structure, and percent cover of crested wheatgrass.

Results of bird density models suggest that only the density of savannah sparrows 

and brown-headed cowbirds were affected by proximity to wells. Density of savannah 

sparrows was twice as high near wells as compared to 700 m away, and the density of 

brown-headed cowbirds was three times higher in study plots containing wells.

Models of bird reproductive success indicate that nest survival did not vary with 

proximity to oil wells for any species, though for Sprague’s pipits nest survival 

decreased as the percent cover of crested wheatgrass increased. However, for some 

species, nest placement and the number of fledglings per successful nest varied as a 

function of proximity to oil infrastructure. Ludlow et al. (2015) found that Sprague’s 

pipits and Baird’s sparrows avoided nesting within 100 m of access trails, and those 

that did nest near trails fledged fewer young. In contrast, Vesper sparrows preferred to 

nest closer to access trails and had higher fledging success near trails, while the fledging success of Savannah sparrows increased with increased proximity to oil wells. 

In a 3-year study in northwestern North Dakota, Thompson et al. (2015) investigated whether songbirds (Baird's sparrow, bobolink [Dolichonyx oryzivorus], 

chestnut-collared longspur, clay-colored sparrow [Spizella pallida], grasshopper sparrow, savannah sparrow, Sprague's pipit, and western meadowlark) and a brood parasite 

(brown-headed cowbird) avoided habitat in proximity to infrastructure associated with 

unconventional oil extraction sites. They recorded mean abundance of each species 
USDA Forest Service RMRS-GTR-384. 2018. 23

along transects emanating from single bore wells, multi-bore wells, and access roads. 

They found that, over all, grassland birds avoided areas within 150 m of multi-bore 

wells; within 267 m of single bore wells; and within 150 m of access roads. Analyzing 

abundance results from each species individually, Thompson et al. (2015) found that 

six species had reduced abundance with increasing proximity to single bore wells 

(Baird’s sparrow, bobolink, chestnut-collared longspur, grasshopper sparrow, savannah 

sparrow, and Sprague’s pipit), while three species, clay-colored sparrow, western meadowlark, and brown-headed cowbird, showed no significant trend in abundance with 

increasing proximity to wells. Likewise, when analyzed individually, the abundance of 

bobolinks and savannah sparrows were found to decrease with increasing proximity to 

access roads, while four species demonstrated no pattern with increasing proximity to 

access roads (brown-headed cowbird, grasshopper sparrow, chestnut-collared longspur, 

and clay-colored sparrow).

Songbirds Summary

Studies of oil and gas development on grassland songbirds focused primarily on 

avoidance behavior, i.e., changes in bird abundance as a function of distance to oil and 

gas related infrastructure (well pads [table 3.2], access roads and trails [table 3.3]). 

Some studies also investigated the relationship between measures of reproductive success and oil and gas infrastructure (table 3.4), or between reproductive success and well 

density (table 3.4). Overall, the magnitude and direction of oil and gas impacts on bird 

abundance and reproductive success varied both between and within species. However, 

one emerging pattern is that the abundance and reproductive success of grassland species that are endemic to the Great Plains (Baird’s sparrow, chestnut-collared longspur, 

McCown’s longspur, and Sprague’s pipit) were more consistently negatively affected 

by proximity to oil and gas infrastructure than non-endemic species. Impacts of oil and 

gas infrastructure on the abundance and reproductive success of non-endemic grassland 

obligates, or generalists, is potentially mediated by other habitat-related variables (e.g., 

topography, vegetation height, and percent cover of invasive grasses, Thompson et al. 

2015).

Grouse

Grouse are considered particularly vulnerable to human development and disturbance because, as a non-migrating species, they require large intact habitats in order 

to acquire the resources needed to survive, reproduce, and persist (Hovick et al. 2014). 

In a meta-analysis on the effect of different types of anthropogenic infrastructure on 

the mean abundance of 19 grouse species (18 of which are suffering from population 

declines), Hovick et al. (2014) found that grouse displayed avoidance behavior of all 

anthropogenic structures, but that they most strongly avoided infrastructure associated 

with oil and gas extraction.

Hovick et al. (2014) also analyzed survival rates and lek attendance across grouse 

species and found significant decreases in annual adult survival and lek attendance in 

the proximity of anthropogenic structures versus habitat far from such structures. An 

increase in predation rates near structures and/or an increase in collision risk could 

explain their lower survival. The presence of anthropogenic structures in open habitats 
24 USDA Forest Service RMRS-GTR-384. 2018.

has been shown to increase the abundance of raptors due to the increase in available 

perch sites, which may in turn result in higher predation rates for birds, reptiles, and 

small mammals in the vicinity of such structures (Fletcher et al. 2003; Slater and Smith 

2010). Grouse are also considered to be at high risk for collisions with anthropogenic 

structures such as fences and power lines, given their poor maneuverability in flight 

(Wolfe et al. 2007).

Several studies have assessed the impacts of oil and gas development on greater 

sage-grouse (Centrocercus urophasianus) populations (reviewed by Naugle et al. 

2011a,b; Riley et al. 2012). The greater sage-grouse is a sagebrush obligate (Schroeder 

et al. 2004) and, like all grouse, requires large intact habitats to maintain robust populations (Hovick et al. 2014). Sage-grouse populations have undergone dramatic declines 

in the past four decades (up to 1.8–11.6 percent annually; Garton et al. 2011) and currently has been extirpated from approximately half of its historic range (Schroeder et 

al. 2004). Energy development is considered a particular threat to this species as studies have demonstrated negative effects of oil and gas development on its abundance, 

reproductive success, and survival.

Studies have shown that sage-grouse avoid areas in proximity to oil and gas developments, leading to decreases in local abundance. For example, Harju et al. (2010) 

found that the presence of oil or gas wells adjacent to lekking grounds decreased male 

attendance at leks by 35–91 percent. Similarly, in a study comparing lek activity in 

1997 to that in 2005–2006, Walker et al. (2007) found that only 38 percent of leks 

located within active gas fields remained active, whereas 84 percent of leks outside 

energy development areas remained active. In Wyoming and Montana, (Doherty et al. 

2008) found that female sage-grouse avoid areas that contain natural gas wells for nesting, even if those areas are otherwise suitable.

The reproductive output and survival of sage-grouse are also negatively affected by 

proximity to energy development. In developed areas, sage-grouse initiate fewer nests 

(Lyon and Anderson 2003), have a greater probability of brood loss for nests they do 

initiate (Aldridge and Boyce 2007), and lower juvenile survival and recruitment to leks 

(Holloran et al. 2010). As with other bird species, both collisions with power lines and 

vehicles in developed areas have been found to be direct sources of sage-grouse mortality (Beck et al. 2006; Aldridge and Boyce 2007).

Burr et al. (2017) compared nest survival of sharp-tailed grouse (Tympanuchus phasianellus) and abundance and identity of known nest predators at two sites, one with 

a well pad density of 0.95 wells/km2, the other with a density of 0.006 wells/km2, in 

western North Dakota. Contrary to the trends found in other grouse species, Burr et al. 

found that nest success of sharp-tailed grouse was 1.95 times higher at the site with 

a high density of well pads. In addition, they found that occupancy rates of the most 

common nest predators (skunks, badgers, raccoons, and coyotes) were 6.9 times higher 

at the low well pad density site. They postulate that common nest predators of sharptailed grouse avoid areas with high well densities, resulting in lower nest predation 

rates.
USDA Forest Service RMRS-GTR-384. 2018. 25

Ungulates

Two reports, Dyke et al. (2011) and Hebblewhite (2008), extensively review known 

and potential impacts of oil and gas development and human disturbance on ungulates 

in North Dakota and Montana, respectively. We refer readers to these reports for a comprehensive review of impacts to ungulate populations. Below we summarize only the 

most recent studies not discussed in those reports.

Ungulates—Pronghorn (Antilocarpa americana)

In a 5-year study of pronghorn (Antilocarpa americana) habitat selection in the 

Jonah and Pinedale Anticline gas fields in western Wyoming, Beckmann et al. (2012) 

analyzed resource selection behavior of 117 female pronghorn at both the individual 

and population level. Covariates in their habitat selection models included: elevation, 

slope, aspect, distance to nearest road, distance to nearest well pad, well pad status, 

habitat loss (labeled disturbance), vegetation, and snow depth.

At the individual level, Beckmann et al. (2012) found that pronghorn were more 

likely to select habitats near well pads (areas approximately 500 m away) versus habitat far from well pads (>2,800 m). However, they also found that well pad placement 

was not random on the landscape, but tended to be located in the most suitable winter 

habitat for pronghorn. Thus, the best winter habitat for pronghorn was often located 

above pockets of natural gas.

Over the course of their 5-year study, Beckmann et al. (2012) found that pronghorn 

increasingly abandoned or lowered usage of critical winter range with increasing construction of well pads and roads in or near those areas. They observed a 5-fold decline 

in the proportion of habitat patches that had a high probability of use by pronghorn 

(28 to 5 percent) and an increase in patches with a low probability of use of pronghorn 

(from 34 up to 53 percent of patches). This change in habitat use by pronghorn tracked 

an increase in well pad and road construction at their study sites.

Beckmann et al. (2012) also found a confounding effect of snow depth on changes 

in habitat use by pronghorn. When snow was deep, pronghorn utilized habitats closer 

to gas wells. They proffer two suggestions for this result. One, that deep snow led to 

an overall reduction in resources and that the pronghorns need for food overrode their 

avoidance behavior; and two, that the pronghorn used the roads to facilitate their movement through the snow.

In a follow-up to their 2012 study, Beckmann et al. (2016) compared body condition, reproductive rates and survival of individual pronghorn between animals that wintered in proximity to the Jonah and Pinedale Anticline Project Area natural gas fields 

to those that wintered in undeveloped areas. They analyzed body mass, stress hormone 

levels (corticosterone), pregnancy rates (vie progesterone), disease exposure and 

ecotoxicology, and estimated survival rates for 388 female pronghorn. They found no 

significant differences for pronghorn wintering inside or outside the boundaries of the 

gas field in any of their response variables, suggesting that while pronghorn avoid these 

habitats, the habitats they frequented outside the well pads are not of lower quality.
26 USDA Forest Service RMRS-GTR-384. 2018.

In a 2-year study on the Missouri plateau in southwestern North Dakota, 

Christie et al. (2017) compared both habitat selection and fawn: female ratios of pronghorn as a function of proximity to oil wells and road density along with other habitat 

variables. They found that habitat selection by pronghorns was negatively correlated 

with road density and areas of human development, but that the pronghorn selected 

foraging areas close to well pads.

Similar to Beckmann et al. (2016), Christie et al. (2017) postulated that pronghorn 

habitat selection in regard to oil well proximity is confounded by the fact that oil wells 

tend to be situated in areas of high-quality pronghorn habitat. Specifically, analysis 

of oil well locations on the landscape found that oil development in North Dakota is 

non-random with respect to land cover types. A significant overlap existed between 

high-value habitats for pronghorn and well pad locations. Fragmentation of these highvalue habitats by well pads and roads may in part explain the correlation between the 

increase in oil and gas development and pronghorn declines in North Dakota (Christie 

et al. 2015).

Ungulates—Rocky Mountain Elk (Cervus elaphus)

In a 4-year study in the Raton basin of northern New Mexico and southern 

Colorado, Dzialak et al. (2011a) estimated Rocky Mountain elk (Cervus elaphus) survival rates as a function of habitat area converted to energy development and number 

of anthropogenic structures per square kilometer (human activity), as well as measures 

of topography and vegetation. They found that an increase in the amount of habitat 

converted to energy development was associated with an increase in mortality risk for 

elk. In contrast, human activity associated with the more locally distributed residential 

and agricultural structures was associated, on average, with reduced risk. They report 

that 22 of 33 fatalities in their study were human-caused, and that roads associated with 

industrial development increased human access to elk habitat, which in turn increased 

risk of mortality by humans (harvest).

Because calving sites selected by female elk can ultimately affect the development 

and provisioning of their new-born calves (Cook et al. 2004), Dzialak et al. (2011b) 

also investigated the effect of human activity associated with energy development on 

resource selection by female Rocky Mountain elk during calving season in the Raton 

basin of southern Colorado. All elk strongly avoided infrastructure associated with 

energy development during the day (but not at night), and parturient elk (those that had 

recently given birth) avoided areas with high road densities during the day. The difference in elk avoidance behavior between day and night suggests that it is the operation 

and maintenance of energy infrastructure, which only occurs during the day, and not 

the mere presence of the infrastructure on the landscape that caused elk to avoid these 

areas (Dzialak et al. 2011b). Elk inside the gas field used cover and elevation to modulate avoidance of human activity during the day.

Ungulates—Mule Deer (Odocoileus hemionus)

In a study on the impacts of energy development on mule deer (Odocoileus 

hemionus), Sawyer et al. (2006) compared winter habitat selection in years before the 
USDA Forest Service RMRS-GTR-384. 2018. 27

development of the Pinedale Anticline Project Area gas field in western Wyoming, 

and years when the gas field was actively being developed. They estimated resource 

selection functions from GPS location data of female mule deer as a function of road 

density, distance to well pads, elevation, slope, and aspect. They found that mule deer 

were less likely to occupy areas in proximity to well pads than those that were farther 

away.

They also found that changes in habitat selection occurred within the first year of 

energy development, and that avoidance of development increased over the course of 

the 3-year study. Overall, Sawyer et al. (2006) found lower predicted probabilities of 

use within 2.7 to 3.7 km of wellsites. They also report that areas classified as having a 

high probability of use by mule deer before gas field development changed to areas of 

low use following development, and that some originally classified as low probability 

of use were used more frequently as the field developed. This suggests that mule deer 

shifted their habitat use to less preferred, and presumably less-suitable habitats, in an 

attempt to avoid infrastructure and/or activities associated with energy development.

In a follow-up study, Sawyer et al. (2009) examined how three types of natural gas 

wells with varying levels of activity affected mule deer winter habitat selection. The 

three types of well pads studied were: wells without active drilling that were connected 

to pipelines; wells without active drilling that were not connected to pipelines (and 

therefore requiring tanker trucks to transport gas); and well pads with active drilling. 

They analyzed over 30,000 GPS locations from 31 adult female mule deer with regard 

to well type, slope and elevation. Results indicated that mule deer avoided all well 

pads, but the strength of their avoidance increased with the level of activity and traffic 

at wells. Specifically, deer avoided areas: within 7.49 km of wells with active drilling; 

within 4.35 km of non-drilling without pipelines (i.e., serviced by tanker trucks); and 

within 3.46 km of non-drilling wells with pipeline gathering systems (i.e., wells with 

no tanker truck traffic).

In a third follow-up report of their ongoing studies with mule deer, Sawyer and 

Nielson (2011) reported that gas field development in western Wyoming led to a 43 

percent decline in mule deer abundance. In this study, Sawyer and Nielson estimated 

mule deer abundance and compared the abundance of a herd that wintered in proximity 

to the Jonah-Pinedale Anticline Project Area (Mesa herd) and a herd that wintered in 

an adjacent winter range with no gas development (the Ryegrass-Soaphole area). They 

examined the long-term trends of both herds (using regression analysis) and found that 

the 10-year (2001–2010) trend in mule deer abundance for the Mesa herd was negative 

and that the abundance of the Mesa herd had declined 43 percent since large-scale gas 

development began. In comparison, the 5-year population trend in the RyegrassSoaphole herd was stable to slightly increasing.

In a study examining the effect of natural gas development on mule deer habitat 

selection, Northrup (2015) collared and observed 53 adult female mule deer on their 

winter range between January 2008 and December 2010 in the Piceance Basin in 

northwestern Colorado. Fitting resource selection functions (RSFs) to deer locations, 

Northrup asked how energy development influenced deer habitat selection and whether 
28 USDA Forest Service RMRS-GTR-384. 2018.

the response of mule deer to energy infrastructure varied with the level of activity at 

well pads (active drilling versus not) and with time of day.

Results indicated that well pads with active drilling elicited the strongest response 

by mule deer. Deer strongly avoided areas within 600 m of well pads with active drilling during both night and day. Deer avoidance behavior differed with time of day for 

distances greater than 600 m: during the day deer could be found within 600–1,000 m 

from drilling well pads, while at night deer avoided all areas within 1,000 m of drilling 

well pads.

Mule deer avoidance of well pads was less severe when no drilling was occurring. 

During the day, deer only avoided areas within 0–600 m of well without active drilling. 

During the night, deer only displayed mild avoidance behavior of areas within 0–400 m 

of these well pads, and no avoidance of areas >400 m. In all cases, the strength of 

avoidance behavior increased with proximity to well pads, with essentially no mule 

deer locations observed within 200 m of well pad edges.

Northrup points out that, summed over the entire “severe winter range” of mule deer 

in the Piceance Basin, oil and gas infrastructure caused mule deer to avoid more than 

one quarter of the range during the night and over half of their available winter range 

during the day.

Aquatic Communities

We found no studies related to the effect of oil and gas development on aquatic 

communities in the LMNG, but Dauwalter (2013) investigated the association of fish 

assemblages with oil and gas well density at 345 sites within the upper Colorado River 

basin of southern Wyoming. Results of this study appear to indicate that some species 

are very sensitive to an increased density of oil and gas wells within the basin. In particular, four species (mottled sculpin, bluehead sucker, brook trout, and rainbow trout) 

demonstrated very low tolerance for oil and gas development and experienced declines 

in occurrence and abundance at well densities less than 0.3 wells per square km.
USDA Forest Service RMRS-GTR-384. 2018. 29

SECTION 4: THREATENED AND ENDANGERED 

SPECIES

Dakota Skipper (Hesperia dacotae)

Introduction

Butterflies are small, charismatic insects that have the potential to serve as valuable 

indicators of ecosystem health (Fleishman and Murphy 2009; New et al. 1995). Many 

species of butterflies are relatively easy to find and measure, occupy low trophic levels, 

and have high reproductive rates that allow them to respond rapidly to changes in their 

environment (Öckinger et al. 2006; Oostermeijer and van Swaay 1998). Butterflies 

can also be used to illustrate the complexity of identifying and solving issues related 

to the conservation of a wide variety of coexisting invertebrates and plants (New et al. 

1995). This may be especially true for butterflies that are prairie specialists, such as the 

Dakota skipper. Many prairie specialists, including the Dakota skipper, have declined 

dramatically because much of their prairie habitat has been lost, primarily by conversion to agriculture (Swengel and Swengel 2015; Swengel et al. 2011). The remaining 

native grasslands are highly fragmented, which restricts prairie specialist butterflies, 

such as the Dakota skipper, to specific isolated habitats where they may be able to persist as small metapopulations (Brückmann et al. 2010; Hanski and Thomas 1994; Petit 

et al. 2001). A metapopulation is a collection of local populations interconnected by 

the processes of local extinction, migration, and colonization/recolonization of vacant 

habitat patches that are essential to the long-term persistence of some species (Hanski 

and Thomas 1994). Habitat specialist butterflies like the Dakota skipper that persist 

as metapopulations may be especially sensitive to reductions in habitat connectivity 

caused by fragmentation (Britten and Glasford 2002; Brückmann et al. 2010; Moranz 

et al. 2014).

Even in areas, such as in western North Dakota, where relatively large areas of native grasslands may have escaped conversion to intensive agriculture because of soils 

or topography, the extraction of petroleum resources has substantially altered the abiotic and biotic characteristics of the remaining prairie communities in a variety of ways 

(Bergquist et al. 2007; Gilbert et al. 2011; Koper et al. 2014; Ludlow et al. 2015; Nasen 

et al. 2011; Preston 2015; Preston and Kim 2016). However, the direct and indirect 

effects of energy development on prairie specialist butterfly populations and habitats 

are largely unknown. This may be especially true for Dakota skipper populations in 

western North Dakota because the area represents the western edge of the range for the 

insect. 

The objective of this section is to synthesize the available information on the features of Dakota skipper habitat and explore how those features may be altered by oil 

and gas development in western North Dakota. Published and unpublished literature 

was used to synthesize information regarding basic life history characteristics and biology of Dakota skipper and its habitat. Little information is available on Dakota skipper 
30 USDA Forest Service RMRS-GTR-384. 2018.

populations and habitats in western North Dakota; consequently, much of the information presented came from studies conducted in the more central part of the range of the 

Dakota skipper.

General Habitat Characteristics of Dakota Skipper

The Dakota skipper (Hesperiidae) is a small butterfly (wingspan of 2.4 to 3.2 cm 

[0.9 to 1.3 inches] (fig. 4.1) that was widely distributed in the northern tallgrass prairie region of North America that existed prior to European settlement (Dana 1991; 

Swengel et al. 2011). Currently, the species is only found in remnants of high-quality 

bluestem prairies in western Minnesota, eastern South Dakota, North Dakota, southern 

Manitoba, and southeastern Saskatchewan (Cochrane and Delphey 2002; FWS 2016a; 

fig. 4.2). Although little information regarding Dakota skipper habitat in western North 

Dakota is available, a common theme among the studies that describe the characteristics of Dakota skipper habitat is an intact prairie containing native grasses that have 

been shown to be major sources of food for developing larvae and forbs that provide a 

diverse source of nectar resources for adults.

Dakota skipper habitat generally occurs on soils found along glacial lake shorelines 

and with gravelly glacial moraine soil deposits. McCabe (1981) described the Dakota 

skipper as a northern Great Plains species associated with calcareous (alkaline) prairies usually found on glacial lake shorelines. Royer et al. (2008) and Rigney (2013) 

described soil characteristics of prairies providing habitat for Dakota skipper in the 

United States and Manitoba, Canada, respectively. All of the sites that were examined 

in the United States and Canada had populations of Dakota skippers at some point in 

time. Both studies reported that the soils on the sites they evaluated were mostly sandy 

loam soils; however, Rigney (2013) found several sites that were classified as clay 

loams (30 to 38 percent clay). The range of soil bulk density values for the two studies 

were similar (0.79 to 1.28 g/m3 for Royer et al. [2008], 0.78 to 1.30 g/m3 for Rigney 

[2013]). Soil pH between the two studies was more variable. Rigney (2013) reported 

pH values that ranged from 6.7 to 7.5 (slightly acidic to slightly alkaline), while Royer 

et al. (2008) reported pH values that ranged from 6.26 to 6.66 (slightly acidic).

Dana (1991) studied the habitat and life history characteristics of Dakota skipper 

and the Ottoe skipper in the 63 ha Hole-in-the-Mountain Prairie Preserve in southwest 

Minnesota. The study was conducted during the 1979 through 1981 field seasons on 

a dry-mesic prairie dominated by mid-height grasses (little bluestem [Schizachyrium 

scoparium], porcupine grass [Hesperostipa spartea], sideoats grama [Bouteloua curtipendula], and prairie dropseed [Sporobolus heterolepis]) and an abundance of nectar 

producing forbs (purple coneflower, also called black sampson echinacea [Echinacea 

angustifolia] and stiff milkvetch [Astragulus adsurgens]). Dakota skippers were fairly 

abundant on the 63-ha site during the study with an estimated annual cohort population 

of 2,000 to 3,000 adults.

Royer and Marrone (1992, as described by Cochrane and Delphey 2002) classified 

Dakota skipper habitat in eastern North Dakota into two types: a low, wet bluestem 

prairie and a drier upland prairie codominated by bluestems and needlegrasses. Wet 

bluestem prairies were generally characterized by low topographic relief (<1 m) with 
USDA Forest Service RMRS-GTR-384. 2018. 31

Figure 4.1—Female (left with obvious wing spots) and male (right with faded spots) Dakota skipper butterflies perched on purple coneflower (Echinacea angustifolia) (photo credit Scott Krych).

Figure 4.2—Locations of Dakota skipper records where the species may still be present based on data 

collected through 2013 (U.S. Fish and Wildlife Service Dakota skipper unpublished geodatabase). Points 

indicate locations where the species has been recorded at least once since 1993 and is reasonably likely to 

still be present. Not shown are locations where Dakota skipper has been recorded, but where FWS considers 

the species to be extirpated or possibly extirpated based on loss of habitat or at least 3 sequential years of 

negative surveys (FWS 2016b).
32 USDA Forest Service RMRS-GTR-384. 2018.

sometimes sandy soils (lacking gravel) that were nearly saturated at depths of 40 to 

60 cm (Royer et al. 2008). The low, wet Dakota skipper sites described by Royer and 

Marrone (1992), and later by Royer et al. (2008) as “Type A” habitats, were similar 

to the glacial lake margins described by McCabe (1981). The drier upland prairies 

(“Type B”) were topographically more diverse with primarily sandy loam soils that 

were sometimes gravelly (Royer et al. 2008). Forbs found on the wet bluestem prairie 

included wood lily (Lilium philadelphicum), harebell (Campanula rotundifolia), and 

smooth camas (Zigadenus elegans) while the upland prairies were characterized by 

coneflowers and blanketflower (Galardia aristata) (Royer and Marrone 1992, as 

described by Cochrane and Delphey 2002). Wood lily and smooth camas (also called 

alkali grass) were also reported as major species in Dakota skipper habitat in North 

Dakota by McCabe (1981). McCabe (1981) described camas as a reliable indicator of 

Dakota skipper habitat (also see Rigney 2013).

Swengel and Swengel (1999a), in a survey of prairie butterflies at 40 sites in Iowa, 

Minnesota, and North Dakota, recorded Dakota skipper populations in only 12 sites in 

Minnesota. These researchers found relatively higher densities of adult Dakota skippers in large (>140 ha) dry prairies in Minnesota that had both upland and lowland 

grassland vegetation. They reported higher abundance of Dakota skippers in hayed 

prairies (24 individuals/km per unit survey) compared to idle prairies (1 individual/

km per unit survey) and burned prairies (3 individuals/km per unit survey). They also 

reported that relative densities of Dakota skippers were positively correlated with longitude in Minnesota (i.e., increased from east to west). For comparison, relative density 

of Poweshiek skipperlings (Oarisma poweshiek) was negatively correlated with both 

latitude and longitude, while relative density of Pawnee skippers (Hesperia leonardus 

pawnee) was positively correlated with latitude and Argos skippers (Atrytone arogos 

iowa) were not correlated with either latitude or longitude (Swengel and Swengel 

1999).

Rigney (2013) reported detailed information on the major biological and physical 

habitat characteristics that provided shelter and forage for larvae and adult Dakota skipper populations in Manitoba, Canada. Nearly all of the sites used in that study were 

characterized by intact mixed to tallgrass prairies containing grasses that were used 

by larvae for feeding. The most common grasses reported in this study included big 

bluestem (Andropogon gerardii), little bluestem, and Cusick’s bluegrass (Poa cusickii). 

Black-eyed Susan (Rudbeckia hirta) was the most common forb species, which was 

also reported by Royer and Marrone (1992).

Habitat Characteristics in Relation to Reproduction and Foraging

Dakota skippers have one generation per year and how the butterfly may interact 

with its habitat in relation to natural and anthropogenic disturbances depends upon the 

life stage of the insect (fig. 4.3). In Minnesota (Dana 1991), adults emerged over about 

a 3-week period (June 24 to July 13) with males emerging about 5 days earlier than 

females (fig. 4.4), while Dakota skipper adults in Canada tended to emerge later than 

in the United States. In southwest Manitoba, Dearborn and Westwood (2014) reported 

that emergence dates for Dakota skipper ranged from July 1 to July 11, while Rigney, 
USDA Forest Service RMRS-GTR-384. 2018. 33

Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul

Adult Emergence

Adult Flight (2 – 4 weeks)

Eggs (8 – 12 days)

1st to 3rd instar larvae (23 – 46 days in shelters in bunchgrasses)

4th instar larvae (16 – 35 days)

4th (or 5th) instar larvae (overwinter in buried shelter)

5th – 6th instar larvae (29 – 40 days

post-diapause in buried shelter)

Pupae (13 – 19 days

in pupal chamber on soil surface)

Adult Emergence

Figure 4.3—Dakota Skipper life history stages and approximate seasonal phenology in Canada (reproduced 

from Rigney 2013).

0

20

40

60

80

100

120

170 175 180 185 190 195 200 205 210 215 220

Julian Date 

0

20

40

60

80

100

120

170 175 180 185 190 195 200 205 210 215 220

Julian Date 

Male

Female

(11) (19)

(42) (62)

Cumulative Percent Emerging

Male

Female

Figure 4.4—Temporal pattern of emergence Dakota skipper adults from hatching in unburned prairie plots 

at the Hole-in-the-Mountain Prairie Preserve in 1981 (upper graph) and 1982 (lower graph). Numbers in parentheses indicate number of individual butterflies (reproduced from Dana 1991 using WebPlotDigitizer, Ankit 

Rohati, Version 3.9, 2015 http://arohatgi.info/WebPlotDigitizer).
34 USDA Forest Service RMRS-GTR-384. 2018.

in her review of emergence in Canada, described emergence as occurring from June 23 

to July 29 with peak emergence between June 27 and July 8 (fig. 4.3).

After emergence, adult Dakota skipper must have regular access to nectar resources, 

although moisture from nectar producing plants may be more critical for adult survival 

to reproduction than nectar (Dana 1991). A review of available feeding studies indicate 

that they can use a wide variety of forb species as sources of moisture and nectar 

(table 4.1). However, only a few plant species receive the vast majority of visits by 

adult Dakota skipper. Purple coneflower and milkvetch were the most frequently used 

plants for nectar in Minnesota (Dana 1991; Swengel and Swengel 1999) while prairie 

goldenrod (Oligoneuron album) was, by far, the species most visited by Dakota skipper in Manitoba, Canada (Rigney 2013). Both purple coneflower and milkvetch were 

absent in the plant surveys reported by Rigney (2013) for Dakota skipper habitat in 

Manitoba. This may suggest a strong preference by adults for purple coneflower and, if 

unavailable, the insects can shift foraging strategies.

After mating, adult females seek out host plants for oviposition. Although grasses 

dominate Dakota skipper habitat, skippers tend to oviposit primarily on forbs that have 

a plant surface wide and smooth enough for the egg to adhere to, such as milkvetch 

(Astragalus spp.) (McCabe 1981). While McCabe (1981) did not observe any oviposition by Dakota skipper on grasses, Dana (1991) reported that Dakota skipper also 

frequently used warm-season grasses, such as big bluestem, little bluestem, sideoats 

grama, and prairie dropseed, for oviposition. As a side note, Dana (1991) was also 

studying the life history characteristics of Ottoe skipper (H. ottoe) at the same study 

site as Dakota skipper and found that over half of the ovipositions made by the Ottoe 

skipper were on purple coneflower, which was not used at all by the Dakota skipper for 

oviposition. Dakota skipper eggs incubate for 7–20 days (average of 10 days) (Dana 

1991). After hatching, the larvae climb down to ground level and construct shelters 

using blades of grass, with preference given to bunchgrasses (little bluestem, for example) and then feed on nearby grass blades with feeding primarily occurring at night 

(McCabe 1981; Dana 1991). The larvae overwinter as fourth or fifth instars (fig. 4.3). 

Overall, the majority of the life span of the Dakota skipper is spent in the larval stage.

Threats and Management of Dakota Skipper Habitat

North American prairies that provide habitat for the Dakota skipper evolved with 

fire and grazing; consequently, these periodic disturbances are considered necessary 

to maintain the structural and functional integrity of native grasslands (Anderson 

2006). Fragmented prairies produced during the conversion to agriculture and urban 

development have greatly reduced the potential for the interacting disturbances of 

fire and grazing to impact grassland ecosystem processes at the landscape scale 

(Fuhlendorf et al. 2009). Because of the widespread conversion of prairies to agriculture, habitat for prairie specialists such as the Dakota skipper is generally rare, occurring infrequently in small isolated patches (Swengel and Swengel 2011, 2015).

Without the natural disturbances of fire and grazing, fragments of high-quality 

prairie that may serve as prime habitat for prairie specialist butterflies often degrade 

because of woody plant encroachment, invasion by exotic plants, and accumulation 
USDA Forest Service RMRS-GTR-384. 2018. 35

Table 4.1—Plant species used as nectar sources for Dakota skippers in North Dakota (McCabe 1981), Minnesota 

(Dana 1991, Swengel and Swengel 1999), and Manitoba, Canada (Rigney 2013). McCabe (1981) did not provide 

quantitative information on frequency of use of specific nectar plants. Dana (1991) and Swengel and Swengel 

(1999a) provided information on frequency of use by sex (M = male, F = female, U = unsexed). Abbreviations for 

Dana (1991) are: V - very common (many hundreds of visits, not enumerated); C = common (about 35 visits); F = 

frequent (11–25 visits); O = occasional (5–10 visits); R = rare (2–4 visits); S = single visit; ̶ = no visits. Species in 

bold face* are listed in the Federal Register as being essential sources of water and nectar for the Dakota skipper 

(“Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Dakota Skipper and 

Poweshiek Skipperling,” 80 Federal Register 190 (October 1, 2015), pp 59248–59384).

Scientific name Common name

McCabe 

(1981)

Dana

(1991) 

(M / F)

Swengel 

& 

Swengel 

(1999)

(M / F / U)

Rigney 

(2013) 

(Adults)

Achillea millefolium Common yarrow R / ̶ 1 / 0 / 0

Agoseris glauca Pale agoseris 1 / 0 / 0 1

Asclepias speciosa Showy milkweed 3 / 1 / 1

Asclepias syriaca Common milkweed 0 / 2 / 0

Asclepias viridiflora Green comet milkweed S / –

Astragalus crassicarpus Groundplum milkvetch 16 / 7 / 5

A. laxmannii (A. 

adsurgens)* Prairie milkvetch C / F

Calylophus serrulatus 

(Oenothera serrulata)* Yellow sundrop X R / R 2 / 1 / 0

Campanula rotundifolia* Bluebell bellflower X

Cardus nutans Knodding plumless thistle 1 / 0 / 4

Chrysopsis sp. Goldenaster 1 / 0 / 0

Cirsium flodmanii Flodman's thistle ̶ / S 3

Cirsium sp. Thistle 0 / 4 / 0

Crepis runcinata Fiddleleaf hawksbeard 2

Dalea candidum

(Petalostemon 

candidum)* White prairie clover 7

D. purpeurea (P. 

purpureus) Purple prairie clover 1

Echinacea angustifolia* Blacksampson echinacea X V / V

75 / 105 / 

10

Erigeron sp.* Fleabane 3 / 0 / 0

Erigeron strigosus Prairie fleabane X R / R

Galium Bedstraw 2 / 0 / 1

Gallardia spp. (aristata)* Blanketflower X

30 / 22 / 

13 6

Lactuca sp. Lettuce 1 / 2 / 0

Lactuca tatarica (L. 

oblongifolla) Blue lettuce S / –

Lilium philadelphicum Wood lily 1 / 0 / 0

Lobelia spicata Palespike lobelia 5

Medicago sativa Alfalfa 1 / 0 / 2

Mellotus officinalis (M. 

alba) Sweetclover ̶ / R 6

Oenothera biennis Common evening primrose 1

Oligoneuron album

(Solidago ptarmicoides) Prairie goldenrod 113

Oxytropis lambertii Purple locoweed F / R 1 / 0 / 0

Penstemon Beardtonque 1 / 0 / 0

Penstemon Beardtonque 2 / 2 / 0

Phlox pilosa Downy phlox X

Ratibida columnifera* Upright prairie coneflower X 3 / 1 / 0

Rudbeckia hirta* Blackeyed Susan R / R 1 / 0 / 0 2

Trifolium hybridum Alsike clover 1 / 0 / 0

Trifolium pratense Red clover O / F

Verbena stricta Hoary verbena 1 / 0 / 0 1

Zigadenus elegans Mountain deathcamas R / ̶ 1 / 0 / 0
36 USDA Forest Service RMRS-GTR-384. 2018.

of litter (Moranz et al. 2012, 2014; Swengel and Swengel 2001; Vogel et al. 2007). 

Swengel (1998) investigated butterfly abundance in relation to 12 categories of increasing intrusive prairie management and found that specialist butterfly abundance, 

including the Dakota skipper, was lowest in sites with no management (the “nothing” 

category). Swengel (1998) concluded that some kind of vegetation management is 

likely required for managing habitats for rare, specialist butterflies.

At the same time, however, it is important to recognize that there may be an unknown level of intermediate management above which butterfly density and diversity 

decreases with increasing management intensity, primarily through the loss of habitat 

for specialist butterflies (Börschig et al. 2013). In general, rotational burning of prairie, described by Swengel (1998) as the most intrusive type of prairie management, 

resulted in lower numbers of prairie specialist butterflies compared to less intrusive 

prairie management practices such as haying or mowing. In this study, almost 10 times 

as many Dakota skippers were found in hayed prairies as were recorded in rotationally burned prairies. Swengel (1996) also reported significantly higher abundance of 

Dakota skippers in hayed prairies compared to burned prairies and indicated that the 

detrimental effects of fire on prairie specialist butterflies could persist for 3 to 5 years.

However, responses of Dakota skipper to fire likely depends on development stage 

and intensity and timing of a burn (fig. 4.3). For example, Dana (1991) found that 

Dakota skipper larvae populations were not adversely impacted by early spring burns 

under low to moderate fuel conditions while late spring burns under moderate to 

high fuel loads caused high larvae mortality. Dana (1991) also found that late season 

fires after adult emergence are likely to adversely impact Dakota skipper populations 

through direct mortality, loss of nectar sources, and reductions in the insulating value of 

litter for overwintering larvae. Collectively, the evidence indicates that using prescribed 

burns to enhance, maintain, or restore prairie habitat for the Dakota skipper should be 

approached with caution. Late season mowing or haying appears to be one of the best 

management practices for prairies supporting Dakota skipper populations (McCabe 

1981; Swengel 1996, 1998).

Tix and Charvat (2005) and Tix et al. (2006) found that removing aboveground 

biomass in a Minnesota tallgrass prairie by burning or by mowing (with raking) had 

similar effects on soil moisture, temperature, inorganic nitrogen, and most plant functional groups. However, haying and mowing are generally not as effective as prescribed 

fire for managing the invasion of exotic perennial grasses such as Kentucky bluegrass 

and smooth brome. Haying and mowing may not be as effective as fire in reducing the 

build-up of litter that may reduce the flowering rate of nectar producing forbs and slow 

development of Dakota skipper larvae and impede their foraging. However, some litter 

helps protect larvae from desiccation during dry conditions (Vogel et al. 2007) while 

also helping to insulate overwintering larvae (Dana 1991).

Further, haying and mowing may not be feasible on topographically diverse prairies 

such as those found in western North Dakota. Livestock grazing may be an alternative 

to prescribed fire, haying, and mowing, but there is a conspicuous lack of information 

that evaluates the specific effects of grazing on prairie specialist butterflies. McCabe 
USDA Forest Service RMRS-GTR-384. 2018. 37

(1981) indicated that the Dakota skipper was intolerant of grazing but provided little 

empirical evidence. Dana (1991) argued that the Dakota skipper appear to decline or 

disappear under heavy grazing, primarily because of vegetation changes that reduce or 

eliminate plants used for oviposition and nectar. This observation is congruent with results reported by Börschig et al. (2013) that indicate a shift from specialist to generalist 

butterflies with increasing land-use intensity, which included livestock grazing.

Despite these cautions, fire can be part of a comprehensive habitat management plan 

for the Dakota skipper along with grazing, haying, and mowing (Dana 1991; Swengel 

1996, 1998). The widespread consensus in the literature is that large uniform application of any treatment should not be used. Because many prairie specialist butterflies, 

including the Dakota skipper, often persist in isolated sites as a series of metapopulations, the preferred approach is to incorporate a variety of small, patchy treatments that 

are scattered and rotated among the site. However, it is important to recognize that how 

Dakota skipper populations may respond to patchy treatments largely depends upon 

their ability to move freely about the site in relation to the physical characteristics of 

the site and the size of the treatments.

Figure 4.5—Intercapture movements of adult Dakota skipper in a mark-and-recapture study (3 years of combined data) at 

the Hole-in-the-Mountain Prairie Preserve (Dana 1991). Arrows indicate direction of movement while bidirectional arrows 

represent recaptures with the same unit as previous capture. Arrow width indicates number of displacements while arrow 

length has no significance. Intercapture map redrawn from Dana (1991) and combined with satellite image of study site 

from Google Earth.
38 USDA Forest Service RMRS-GTR-384. 2018.

0

100

200

300

400

1979 1980 1981

Distance (m) 

Intercapture Distance 

Males

Females

0

5

10

15

1979 1980 1981

Days 

Days Between Captures 

Males

Females

Dana (1991), in a mark and recapture study of Dakota skipper in Minnesota prairie, 

subdivided the 63-ha study site into four units (fig. 4.5). While capture rates varied 

among the four units, densities of male and female Dakota skippers were highest in 

Units A and D, intermediate in Unit B, and lowest in Unit C. Most intercaptures were 

within the same unit, although Dana (1991) reported no statistical difference between 

within-unit intercaptures and among-unit captures, despite the small amount of movement across the tributary ravine that separated Units A and D from Units B and C (fig. 

4.5). From a management perspective, the intercapture movements of this study suggest that division of Dakota skipper habitat into distinct management units that can be 

treated in rotation may reduce the potential detrimental effects of any one treatment to 

the population (also see Swengel 1996, 1998; Moranz et al. 2014). However, the success of one or more treatments (burning, grazing, mowing, haying), applied singly or 

rotationally, to restore prairie butterfly habitat may ultimately depend upon the dispersal ability of the species. Moranz et al. (2014) found that regal fritillary adults, which 

are good dispersers, were able to quickly recolonize (within 5 months) areas where the 

butterfly population was completely destroyed by fire.

Figure 4.6—Mean intercapture distances (m) and days between recaptures for Dakota skipper in a mark and 

recapture study at the Hole-in-the-Mountain Prairie Preserve (Dana 1991). Vertical bars are standard errors. 
USDA Forest Service RMRS-GTR-384. 2018. 39

Although Dana (1991) reported that most recaptures of Dakota skipper were in the 

same unit as the preceding capture, movement between metapopulations in the units 

were common. Intercapture distances ranged from 104 m to 272 m and varied among 

sample years (fig. 4.6). Collectively, these results suggest that Dakota skippers have 

the ability to disperse fairly freely, at least within this study site, even considering the 

potential of the tributary ravine to serve as a partial barrier to movement (Dana 1991). 

Connectivity among populations, along with high population numbers, is very important for maintaining genetic diversity (Britten and Glasford 2002).

These results also suggest that careful planning of treatments within this site could 

reduce the potential for treatments to adversely affect the Dakota skipper populations 

at the site level. For example, the higher abundance and greater movement of the butterflies in Units A and D suggest that these units could be subdivided into possibly 

four management units where treatments, including prescribed fire, could be rotated, 

which would ultimately increase the abundance of the butterflies in these units. In this 

example, higher abundance in Units A and D could serve as population sources for 

Units B and D that were also undergoing treatments, although treatments should not be 

applied at the same time as Units A and D.

Dakota Skipper Critical Habitat on the Little Missouri National Grassland

Critical habitat for the Dakota skipper, as described in the Federal Register 

[“Endangered and Threatened Wildlife and Plants: Designation of Critical Habitat for 

the Dakota Skipper and Poweshiek Skipperling,” 80 Federal Register 190 (October 1, 

2015), pp 59248 – 59384], includes the physical or biological features essential to the 

conservation of the species. These features include three primary constituent elements 

(see Federal Register for more detail):

1. Wet-mesic tallgrass or mixed-grass remnant untilled prairie that occurs on nearshore glacial lake soil deposits or high-quality dry-mesic remnant untilled prairie on 

rolling terrain consisting of gravelly glacial moraine soil deposits;

2. Native grasses and native flowering forbs for larval and adult food and shelter;

3. Dispersal grassland habitat that is within 1 km (0.6 mile) of native high-quality remnant prairie (as defined by primary constituent element 1) that connects high-quality 

wet-mesic to dry tallgrass prairies or moist meadow habitats. Dispersal grassland 

habitat consists of undeveloped open areas dominated by perennial grassland with 

limited or no barriers to dispersal including tree or shrub cover less than 25 percent 

of the area and no row crops such as corn, beans, potatoes, or sunflowers.

The Federal Register indicates that either prairie dropseed or little bluestem be 

available to provide food and shelter sources during Dakota skipper larval development 

[“Endangered and Threatened Wildlife and Plants: Designation of Critical Habitat for 

the Dakota Skipper and Poweshiek Skipperling,” 80 Federal Register 190 (October 1, 

2015), pp 59248 – 59384]. The Federal Register also indicates that one or more of a variety of native forb species serve as nectar and water sources for adult Dakota skipper. 

All of the forbs listed in the Federal Register have been reported to have been used as 

sources of nectar (and/or water) by Dakota skipper (highlighted in table 4.1). One species, prairie goldenrod (Oligoneuron album [Solidago ptarmicoides]), was absent from 
40 USDA Forest Service RMRS-GTR-384. 2018.

the list of forbs in the Federal Register but was described by Rigney (2013) as being 

frequently visited by Dakota skipper in Manitoba, Canada.

The U.S. Fish and Wildlife Service (FWS) has designated two sites within the 

LMNG as meeting the essential elements necessary to serve as critical habitat for 

the Dakota skipper [“Endangered and Threatened Wildlife and Plants: Designation 

of Critical Habitat for the Dakota Skipper and Poweshiek Skipperling,” 80 Federal 

Register 190 (October 1, 2015), pp 59248 – 59384]. Both sites are located in McKenzie 

County, North Dakota (fig. 4.7) in areas of oil and gas development. Energy development in this area is experiencing rapid expansion because horizontal drilling and 

hydraulic fracturing (i.e., fracking) techniques have allowed cost-effective extraction of 

difficult-to-access oil resources (North Dakota Industrial Commission 2014). Satellite 

images (8/15/2013 images from Google Earth) were used to get a current general 

perspective of oil and gas development in proximity to the two sites on the LMNG 

(fig. 4.8). The North Dakota Industrial Commission has predicted that 2,000 new oil 

wells will be drilled annually from 2014 to 2034.

Ecological site maps were also developed for the two sites using the Natural 

Resource Conservation Service Web Soil Survey (U.S. Department of Agriculture 

2015; figs. 4.9 and 4.10). Loamy, Thin Loamy, and Shallow Loamy are the dominant 

Ecological Sites (ESs) for the two critical habitat areas. Ecological Site Descriptions 

(ESDs) for the three ESs are currently described by the Natural Resource Conservation 

Service as provisional. In the reference state, all three ESs are dominated by mixedgrass prairie species with approximately 80 to 85 percent of the annual biomass production coming from grass and grass-like species, 10 to 12 percent from forb species, 5 

to 7 percent from shrub species and 0 to 1 percent from cryptograms.

Only one of the provisional ESDs (Thin Loamy) contains both little bluestem and 

prairie dropseed in the reference plant community. These two species were specifically 

identified by the FWS as essential species for Dakota skipper larvae development. 

Little bluestem and prairie dropseed respectively comprise about 7 to 9 percent and 0 to 

1 percent of the total biomass in the reference plant community for the Thin Loamy ES 

(unfavorable years vs. favorable years). The ESD for the Shallow Loamy ES indicates 

that little bluestem comprises 9 to 14 percent of the total biomass for unfavorable and 

favorable years, respectively. The Loamy ES is dominated primarily by western wheatgrass and green needlegrass in the reference state with increasing amounts of blue 

grama with continuous livestock grazing. Little bluestem and prairie dropseed were not 

part of the ESD for the Loamy ES. Several of the forbs listed in table 4.1 as serving as 

sources of nectar and water are included in the ESDs for the three Ecological Sites.

Extraction of oil and gas resources has the potential to directly impact critical 

habitat for the Dakota skipper on these two sites through construction of well pads, 

compressor stations, and roads and indirectly through increased vehicle traffic and its 

accompanying dust that extends its impact well beyond the road surface. However, 

specific information on how oil and gas development may impact prairie specialist butterflies and their habitat is essentially nonexistent. Because prairie specialist butterflies 
USDA Forest Service RMRS-GTR-384. 2018. 41

Figure 4.7—Dakota skipper critical habitat in McKenzie County, ND (Federal Register, Vol. 80, No. 190, 

October 1, 2015).
42 USDA Forest Service RMRS-GTR-384. 2018.

Figure 4.8—Outline of Dakota skipper habitat in McKenzie County, ND (8/15/2013 images from Google Earth).

Dakota Skipper Critical Habitat, North Dakota Unit 11, McKenzie County

Dakota Skipper Critical Habitat, North Dakota Unit 12, McKenzie County
USDA Forest Service RMRS-GTR-384. 2018. 43

Figure 4.9— Provisional Ecological Site (ES) map for North Dakota Critical Habitat North Dakota Unit 11 

(E3107F = Cabba-Badland complex, 6 to 70% slopes, Shallow Loamy ES; E3541C = Williams-Zahl Loams, 

6 to 9% slope, Loamy ES [39%], Thin Loamy [36%]; E3555D = Zahl-Williams loams, 9 to 15% slopes, Thin 

Loamy [45%], Loamy [36%]; E3607F = Zahl-Cabba-Arikara complex, 9 to 70% slopes, Thin Loamy [30%], 

Shallow Loamy [20%], Not Assigned [20%]; E3609F = Zahl-Cabba-Maschetah complex, 6 to 70% slopes, 

Thin Loamy [30%], Shallow Loamy [20%]). Percentages in brackets [ ] represent percentage of ES in the 

portion of the map outlined in blue.

Figure 4.10—Provisional Ecological Site (ES) map for North Dakota Critical Habitat North Dakota Unit 12 

(E2120B, Farnup loam, 2 to 6% slopes, Loamy [61%]; E3567, Zahl-Max loams, 15 to 45% slopes, Thin 

Loamy [50%]; Loamy [42%]; E3555D = Zahl-Williams loams, 9 to 15% slopes, Thin Loamy [45%], Loamy 

[36%]’ E3609F = Zahl-Cabba-Maschetah complex, 6 to 70% slopes, Thin Loamy [30%], Shallow Loamy 

[20%]. Percentages in brackets [ ] represent percentage of ES in the portion of the map outlined in blue.
44 USDA Forest Service RMRS-GTR-384. 2018.

are typically year-round residents within small prairie remnants and tend to have 

close associations with specific native plant species (larval host species and nectar resources), they may be especially vulnerable to even subtle changes in their habitat due 

to energy development.

Preston and Kim (2016) estimated that construction of well pads in the Williston 

Basin from 2000 to 2015 directly converted approximately 12,990 ha of land to energy 

development with an additional 12,121 ha disturbed, some of which was reclaimed. 

About 47 percent of the converted land came from prairies. The estimates of conversion and disturbance did not include energy development infrastructure (roads, 

pipelines, or storage tanks). Evidence of land conversion and associated disturbances 

and infrastructure related to energy development can be seen around the two areas designated as critical habitat by the FWS (fig. 4.7). Dust from road traffic can physically 

affect photosynthesis, respiration, and transpiration, which often reduce productivity 

and alter plant composition and structure of communities of plants along roadsides (see 

review by Farmer 1993). Construction of well pads and infrastructure are disturbances 

that often lead to increases in non-native species that can extend beyond the physical 

footprint of the original disturbance (Preston 2015).

Preston (2015) found, compared to control sites, significantly more non-native species richness and cover near well pads constructed 5 and 10 years ago in the Williston 

Basin. The distribution of non-native species extended about 50 m from the sampled 

well pads, which may serve as source of propagules for non-native expansion into the 

surrounding native grasslands (also see Nasen et al. 2011). Roads are often recognized 

as conduits for the spread on non-native species (Gelbard and Belnap 2003). Creuzer et 

al. (2016) reported that increased energy development activity in the Bakken Region of 

western North Dakota significantly increased road dust, but the increased dust loading 

was restricted to less than 40 m from the road centerline.

Several of the non-native species (thistle, lettuce, and sweetclover) recorded by 

Preston (2015) have been identified as nectar sources for Dakota skipper (see table 

4.1). Possibly the greatest threat to Dakota skipper habitat in the two critical habitat 

areas on the LMNG may come from non-native perennial grasses. Preston (2015) 

reported high cover of crested wheatgrass (Agropyron cristatum), smooth brome 

(Bromus inermis), Kentucky bluegrass (Poa pratensis), and intermediate wheatgrass 

(Thinopyrum intermedium) near well pads and in control sites. Non-native perennial grasses have slowly and inexorably transformed large tracts of native grasslands 

(DeKeyser et al. 2013), substantially degrading the habitat for prairie specialist butterflies (Swengel and Swengel 2015). The widely spaced stems of the strongly rhizomatous smooth brome may reduce the ability of the skipper larvae to construct adequate 

shelters (Dana 1991). Kentucky bluegrass may by more suitable for skippers; however, 

the mid-summer pattern of senescence or dormancy in Kentucky bluegrass is likely to 

reduce its suitability as habitat for skipper larvae. Crested wheatgrass and intermediate 

wheatgrass likely provide similar barriers to habitat suitability.

Invasion of non-native plants, especially aggressive non-native perennial grasses 

such as smooth brome and Kentucky bluegrass, and road dust could also adversely 
USDA Forest Service RMRS-GTR-384. 2018. 45

impact the ability of Dakota skipper to utilize portions of North Dakota Critical Habitat 

12 (fig. 4.8). A road of about 8 m wide (25 ft) and potential impact of invasive plants 

and dust of about 50 m (163 ft) on both sides of the road likely does not represent a 

substantial direct loss of Dakota skipper habitat for this site. However, collectively the 

108-m boundary of the road may significantly reduce the ability of the Dakota skipper 

to freely move about the site, possibly effectively eliminating dispersal to habitat on 

the north and east side of the road. The well pad adjacent to the critical site represents 

a disturbance of about 1.6 to 2.8 ha (4 to 7 acres) (Preston and Kim 2016), which does 

represent a substantial barrier to dispersal in and out of the critical habitat site.

Summary

The Dakota skipper is a small, prairie specialist butterfly that was widely distributed 

in the northern tallgrass prairie region of North America that existed prior to European 

settlement. Many prairie specialist butterflies such as the Dakota skippers have declined dramatically because much of their prairie habitat has been lost, primarily by 

conversion to agriculture. The remaining native prairies are highly fragmented and that 

restricts prairie specialist butterflies, such as the Dakota skipper, to specific, isolated 

habitats that often require some type of management. However, prairie butterflies are 

often sensitive to the very disturbances needed to maintain the high-quality prairie necessary for their persistence, thus creating a “prairie butterfly paradox” created largely 

because of the severe loss of functional habitat (Schlicht et al. 2009).

Several patterns emerge from the literature that allow predictions about how disturbances such as fire, grazing, mowing, and haying, acting singly and interactively, 

may impact the Dakota skipper habitat and populations. Late season mowing or haying 

appears to be one of the best management practices for prairies supporting Dakota 

skipper populations, while using prescribed burns should be approached with caution. 

However, haying and mowing are generally not as effective as prescribed fire for 

managing the invasion of exotic perennial grasses. Further, haying and mowing may 

not be feasible on topographically diverse prairies such as those found in western North 

Dakota. The general consensus in the literature is that large uniform application of any 

treatment should not be used. Because many prairie specialist butterflies, including the 

Dakota skipper, often persist in isolated sites as a series of metapopulations, the preferred approach is to incorporate a variety of small, patchy treatments that are scattered 

and rotated among the site. However, it is important to recognize that how Dakota skipper populations may respond to patchy treatments largely depends upon their ability to 

move freely about the site in relation to the physical characteristics of the site and the 

size of the treatments.

While some areas such as those in western North Dakota have escaped conversion 

to intensive agriculture because of soils or topography, the extraction of petroleum 

resources has substantially altered abiotic and biotic characteristics of the remaining 

prairie communities in a variety of ways. The FWS has designated two sites within the 

LMNG as meeting the essential elements necessary to serve as critical habitat for the 

Dakota skipper. Both sites are located in McKenzie County, North Dakota, in areas of 

oil and gas development. Construction of well pads and infrastructure are disturbances 
46 USDA Forest Service RMRS-GTR-384. 2018.

that often lead to increases in non-native species that can extend beyond the physical 

footprint of the original construction. While several non-native species of forbs have 

been identified as nectar sources for Dakota skipper, the greatest threat to Dakota skipper habitat in the two critical habitat areas on the LMNG may come from non-native 

perennial grasses. Construction of well pads and energy development infrastructure 

may provide barriers to the free movement of Dakota skipper among habitat patches 

within a site.

Sprague’s Pipit (Anthus spragueii)

Introduction

Grassland birds, including ducks, grouse, hawks, and songbirds, have experienced 

the greatest and most geographically widespread declines among grassland vertebrates 

(Samson and Knopf 1994). Therefore, they are one of the most widely and intensively 

monitored of the groups in the grasslands (Kalyn-Bogard and Davis 2014). One 

grassland species, the Sprague’s pipit (Anthus spragueii, Audubon 1844), is a primary 

endemic commonly associated with native grassland (Ludlow et al. 2015) and its status 

for listing is warranted but precluded.

Sprague’s pipit is approximately 17 cm in length with a prominent dark eye on a 

pale buff face. It has pale edges on rounded back feathers that make it appear as though 

it has scales. Whitish underparts, short dark streaks on the breast, and pinkish legs are 

some of the other prominent characteristics. One of the features differentiating it from 

a closely related species, the American pipit (Anthus rubescens), is its more extensively 

white outer tail feathers. The call is a loud squeet in a pattern of two or more while the 

song is a series of tzee and tzee-a notes that are sung while in continuous flight (Dunn 

and Alderfer 2011). The first documented specimen was recorded near Fort Union, 

North Dakota, in 1843 and was named for Audubon’s artist Isaac Sprague (Allen 

1951).

The breeding range for Sprague’s pipit in the United States is primarily in the central 

mixed-grass prairie of the northern Great Plains including: north-central and eastern 

Montana, North Dakota, and northwestern to north-central South Dakota (fig. 4.11). 

The spring migration through the central Great Plains occurs in April and May while 

the fall migration takes place in late September through early November (cited in Davis 

et al. 2014, fig. 1; and Jones et al. 2010).

Habitat and Diet Characteristics of Sprague’s Pipit (Anthus spragueii)

Sprague’s pipits prefer large native grassland areas for both breeding and wintering 

habitat with the most favorable wintering habitats reaching ~10,000 acres (Davis et al. 

1999; Jones 2010). Little is known about their habitat use along their migration routes 

other than indications that preferred migratory habitat has similar characteristics to 

breeding and wintering habitat (Davis et al. 2014). Breeding range habitat consists of 

grazed rangeland made up of native mixed-grass prairie with low shrub cover (Davis et 

al. 1999; Lusk and Koper 2013). Studies describing dominant grasses in native mixedgrass prairie demonstrate an affinity for native wheatgrass species (table 4.2).
USDA Forest Service RMRS-GTR-384. 2018. 47

In general, nest sites for grassland birds in northern Montana had greater foliage 

height and density than randomly selected sites (Dieni and Jones 2003). Sprague’s pipit 

nest sites in Montana and Saskatchewan were characterized by tall plants (31.7 cm), 

moderate amounts of litter (10.9 percent cover and 11.2–18.2 cm depth), and vegetation density yielding visual obstruction between 11.2–14 cm (Dieni and Jones 2003; 

Lusk and Koper 2013). Areas with prickly pear cactus and clubmoss were avoided for 

nesting (Dieni and Jones 2003). Daily nest survival declined significantly with increasing vegetation density and litter depth. Daily nest survival declined by 76.4 percent for 

each 5-cm increment increase in vegetation density as measured by visual obstruction 

(Lusk and Koper 2013). Sprague’s pipit is more common in native grassland rather 

than planted grassland and their abundance increased in patches (e.g., 256-ha sections) 

adjacent to native grassland rather than other landscape types (crop or planted; Davis et 

al. 2013).

Figure 4.11—Distribution map of Sprague’s Pipit (Anthus spragueii) (Davis et al. 2014).
48 USDA Forest Service RMRS-GTR-384. 2018.

Sprague’s pipits can occupy planted grasslands with similar structure to native 

grasslands but with lower abundance indicating the importance of preserving and 

enhancing native grassland over seeding cultivated lands to provide Sprague’s pipit 

habitat.

Sprague’s pipit diets consist primarily of arthropods during all times of the year 

(Davis et al. 2014). Plant material only accounted for 6 percent of what was present 

in stomach samples (Maher 1979). Nestlings in Saskatchewan, Canada, shifted the 

species of arthropods they consumed as the season progressed likely due to changes in 

arthropod availability (Maher 1979). Even with abundant food sources, Sprague’s pipit 

nestling diets had larger amounts of spiders when compared to other passerine species 

(Maher 1979).

Threats and Management of Sprague’s Pipit Habitat

Both small- and large-scale conversion of native grasslands to other uses, including 

cropland and infrastructure supporting human industries, is a threat to Sprague’s pipit 

habitat. An estimated 60 percent of native grasslands have been converted in the United 

States (Higgins et al. 2002). Sprague’s pipits avoid cropland edges, declining in abundance by 25 percent or more within almost 1 kilometer of cropland edges (Davis et al.; 

2014; Koper et al. 2009; Sliwinski and Koper 2012). Edge effects can greatly magnify 

the effects of habitat loss. Pipit use of cultivated land that has been seeded with exotic 

grasses and forbs is dependent on how much native grassland habitat is nearby (Davis 

et al. 2013). Sprague’s pipits will occur significantly more in native and seeded pasture 

than hayland and cropland (Davis et al. 1999). In southern Saskatchewan, no Sprague’s 

pipit nests were found on cropland converted to hayland (McMaster et al. 2005). Daily 

survival rates were similar between planted hayfields and native grassland but the 

nesting sites did not persist year to year (Davis et al. 2014). Haying may disturb the 

sites, preventing renesting. Conservation of native grassland combined with a mosaic 

of lightly to heavily grazed areas is the best way to meet the habitat requirements for 

all grassland species (McMaster et al. 2005). Preservation and enhancement of existing 

native grassland areas is necessary to maintain adequate Sprague’s pipit habitat.

The effect of grazing on Sprague’s pipit habitat depends on grazing intensity, moisture, soil types, and plant species composition (Davis et al. 2014). Grazing from May to 

September (0.45 AUM per hectare) did not alter nest survival of Sprague’s pipit (Lusk 

and Koper 2013). However, Sprague’s pipits were negatively associated with heavy 

grazing and found to occur twice as much in lightly to moderately grazed pastures 

(Davis et al. 1999). Vegetation differences driven by grazing rather than the identity 

of the herbivore drives Sprague’s pipit’s response to grazing. For example, Sprague’s 

pipits were found on cattle plots but not bison plots, but this difference was likely due 

to the higher shrub densities on the bison plots (Lueders et al. 2006). Sprague’s pipit 

differs from many other grassland specialists in that they did not use prairie dog towns 

as habitat in Chihuahua, Mexico (Manzano-Fischer et al. 1999), but their habitat use of 

prairie dog towns may differ in their northern breeding range (e.g., North Dakota).

Oil and gas infrastructure and its associated road development has the potential to 

affect Sprague’s pipit. Sprague’s pipit abundance decreased with increased well density 
USDA Forest Service RMRS-GTR-384. 2018. 49

(Dale et al. 2009; Hamilton et al. 2010, 2011). Disturbances caused by all-terrain 

vehicles, trucks, or pedestrian traffic can potentially alter reproductive behavior by 

disturbing male aerial displays (Dale et al. 2009). In the grasslands of southern Canada, 

Sprague’s pipits were significantly less abundant (reduced by ~50 percent) 150 and 

250 m from natural gas and traditional oil developments as compared with sites 350 m 

away (Linnen 2008). In western North Dakota, Sprague’s pipits were more sensitive to 

oil well and road development than other grassland species and avoided areas within 

350 m of single bore well pads (Thompson et al. 2015).

However, Sprague’s pipits may be unaffected by low-traffic roads (Koper et al. 

2009) but were 26 percent less abundant along road transects when compared with trail 

transects (Sutter et al. 2010). Pipeline construction impacted both the nest survival and 

number of chicks surviving to day 8 as both increased with distance from a pipeline 

right-of-way (ROW) in southern Canada. Distances of 0 m, 350 m, and 1,000 m translated into nest success estimates of 29, 43, and 62 percent, respectively (Sutter et al. 

2016). Vegetation close to the ROW may play an important role affecting nest success. 

Further, noise levels associated with construction and clean-up next to ROW occurred 

at levels that would interfere with calls and songs within 350 m of the ROW. A restricted activity period from 1 May to 31 August and a 350-m setback distance could 

encourage better nest success near pipeline ROWs (Sutter et al. 2016; Thompson et al. 

2015).

Vegetation near infrastructure and road developments is typically altered and this 

could be a primary reason why Sprague’s pipits avoid them. Areas next to oil leases 

and access roads were dominated by dense weedy vegetation such as smooth brome 

(Bromus inermis) and sweet clover (Melilotus spp.), suggesting that anthropogenic 

activities and introduced vegetation are simultaneously contributing to the avoidance of Sprague’s pipits to these sites (Linnen 2008). Crested wheatgrass (Agropyron 

cristatum) was pointed out as a species of non-native grass that Sprague’s pipits tend 

to avoid and is known to be associated with industrial development sites (Hamilton et 

al. 2010, 2011). Increased shrub cover is associated with declines in Sprague’s pipit 

(Lueders et al. 2006).

 Nest predation is also a threat to Sprague’s pipit and is the primary cause of nest 

failure (Davis 2003; Jones et al. 2010). Mortality of Sprague’s pipit typically occurs 

at the juvenile stage of development as there are no published accounts of adults being predated (Davis et al. 2014). A list of predators identified in Davis et al. (2012) 

that have been documented predating on Sprague’s pipit eggs and nestlings includes: 

thirteen-lined ground squirrel (Ictidomys tridecemlineatus), vole (Microtus spp.), 

mouse (Peromyscus spp.), deer (Odocoileus spp.), striped skunk (Mephitis mephitis), 

coyote (Canis latrans), northern harrier (Circus cyaneus), black-billed magpie (Pica 

hudsonia), western meadowlark (Sturnella neglecta), and gartersnake (Thamnophis

spp.) Changes in the landscape due to oil and gas development could impact the predator communities in ways that will either positively or negatively affect Sprague’s pipit. 

Several of the predatory bird species might gain advantage of perches on newly constructed infrastructure. Direct competition with other birds could also be another threat. 
50 USDA Forest Service RMRS-GTR-384. 2018.

However, Sprague’s pipit is mostly a solitary species and most antagonistic behavior 

occurs between males guarding territory against conspecifics (Davis et al. 2014).

Summary

The Sprague’s pipit is a native grassland bird species that breeds within the remaining mixed-grass prairies of the LMNG that has been warranted but precluded from 

listing as a threatened or endangered species under the Endangered Species Act. This 

species shows a preference for large tracts of undisturbed native grassland areas with 

several studies indicating a preference for native vegetation, low shrub cover, and 

greater foliage height. Sprague’s pipits primarily forage on arthropods during all times 

of the year. Habitat loss through conversion to crops, infrastructure supporting human 

activities, and cattle grazing represents the greatest threat to this species.

Northern Long-Eared Bat (Myotis septentrionalis)

Introduction and North Dakota Status

Although there are 11 bat species in North Dakota, the northern long-eared bat 

(Myotis septentrionalis) is the only bat species listed Federally as threatened (Barnhart 

and Gillam 2016). The northern long-eared bat is insectivorous and generally brown in 

color with ears and tail that are longer than conspecifics of its size. They prefer wooded 

habitat and generally roost under the loose bark or within cavities of trees with hibernacula located in caves and mine shafts.

Figure 4.12—Map from Nelson et al. (2015) depicting sites for Statewide bat survey in North Dakota.
USDA Forest Service RMRS-GTR-384. 2018. 51

In North Dakota, the species is considered to be seasonal because no hibernacula have 

been identified (Barnhart and Gillam 201; Dyke et al. 2015). During the summers of 

2009–2012, a Statewide survey captured 18 individuals along the Missouri River Valley 

and five individuals in the badlands, which included sites in the LMNG, Theodore 

Roosevelt National Park, and Little Missouri State Park (fig. 4.12). There were no detections of northern long-eared bat using echolocation call sequences but it is difficult to 

distinguish between species of Myotis spp. using this technique (Nelson et al. 2015).

The top three predictive environmental variables used to model the northern long-eared 

bat habitat suitability map were: mosaic forest or shrubland (50–70 percent) / grassland 

(20–50 percent), max temperature of warmest month, and mean temperature of warmest 

quarter (Barnhart and Gillam 2016). Using this habitat suitability modeling technique, 

highly suitabile habitat for northern long-eared bats does occur outside of current 

International Union for Conservation of Nature distributions in North Dakota (fig. 4.13).

Threats and Management of Northern Long-Eared Bat Habitat 

(Myotis septentrioalis)

The threats to northern long-eared bats are numerous and include many that are 

anthropogenic. The petition to list by Matteson (2010) includes “habitat loss and degradation driven by agricultural and residential development, logging, mining or other 

resource extractive practices, environmental contaminants, disturbance by vandalism or 

recreation, and climate change” as factors negatively influencing the persistence of this 

species. Research regarding threats or effects of these threats is lacking and therefore 

most recommendations available are subjective.

White nose syndrome (WNS) is a disease affecting bats in their hibernacula that 

was discovered in New York in the winter of 2006–2007. It is a white fungus that 

presents on the muzzle, ears, and/or wing membranes of infected bats (Matteson 2010). 

Research is ongoing to determine how exactly this fungus is affecting bats and current 

Figure 4.13—Habitat suitability map from Barnhart and Gillam (2016) demonstrating high suitability habitat 

(red) outside of currently documented International Union for Conservation of Nature range map (cross hatch).
52 USDA Forest Service RMRS-GTR-384. 2018.

findings have established that the primary cause of death is starvation (Matteson 

2010). The means of spread are thought to be from cavers and researchers (initially 

from Europe) and once established in a hibernacula it can then spread from bat to bat. 

Although this threat has not been reported in bat species in North Dakota, it is the 

primary reason for listing the species as threatened and efforts are underway to identify 

any hibernacula in the State in order to monitor populations for detection of WNS.

Agricultural and residential development are listed by the Matteson (2010) petition 

with the general argument that human population growth will increase development 

particularly along riparian areas and in temperate forests, which are habitat used by 

the northern long-eared bat. The conversion of natural landscapes to industrial agriculture operations that use pesticides, fertilizers, and irrigation can lead to reduced food 

availability for bats. The concern of commercial logging operations in the northern 

long-eared bat’s range is primarily focused on New England’s northern forest. With 

that consideration, Matteson (2010) cites a report that demonstrates the need for keeping larger than average diameter trees and higher than average snag density in forested 

areas.

Wind energy development is another potential source of mortality for northern 

long-eared bats and the North Dakota State Wildlife Action Plan states that “several 

turbine farms are under construction in parts of North Dakota” (Dyke et al. 2015) while 

Figure 4.14—Wind energy map for western North Dakota (Stults 2016).
USDA Forest Service RMRS-GTR-384. 2018. 53

several sites already exist in areas that may affect northern long-eared bats (fig. 4.14). 

A published survey of bat mortalities at wind energy facilities in North Dakota found 

nine bat carcasses from two species from only six surveys at 12 turbines (Bicknell and 

Gillam 2013). Eight of the nine were hoary bats (Lasiurus cinereus) and one was a 

silver-haired bat (Lasionycteris noctivagans). The researchers hope that their preliminary survey will demonstrate a need for more in-depth surveys of bat mortality at wind 

energy facilities in North Dakota. Concerning northern long-eared bats specifically, no 

northern long-eared bats have been reported killed in the Upper Midwest, perhaps suggesting that wind energy may not be a principal threat to northern long-eared bats but 

still a threat to other species of bats (Kunz et al. 2007).

In a report on the impacts of shale gas development on bats, Hein (2012) admits that 

the possible adverse influence these operations have on bat populations is unknown. 

Hein writes about the impacts of high-volume hydraulic fracturing (HVHF) from what 

we know ecologically. Hein subjectively applies that knowledge to inform about potential threats associated with these actions. Water withdrawal from hydric habitats near 

any shale gas development could affect roost site selection and abundance/availability 

of prey, an issue that would be exacerbated by drought conditions or ephemeral water 

sources. Compounding the potential loss of water resources is the possibility of contaminating existing water sources or adding water sources that may have contaminates. 

Some contaminants reported in HVHF processes include three heavy metals: cadmium, 

mercury, and lead, which are all associated toxins in several wildlife studies cited by 

Hein (2012). These contaminants can be ingested directly from drinking water but also 

through prey items in which the dietary accumulation and metabolic capacity increase 

at the higher trophic level.

Shale gas development coupled with logging may further reduce the limited amount 

of habitat available for this species. The northern long-eared bat foraged almost exclusively in closed canopy systems and avoided open areas in a West Virginia study 

(Owen et al. 2003). However, it would be interesting to determine how much this 

species relies on closed canopy habitat in the North Dakota landscape that it inhabits. 

Hein (2012) suggests protecting any habitat surrounding hibernacula from development 

or disturbance, citing drilling operations in particular because any additional arousals 

of hibernating bats can reduce the amount of fat reserves available to the bat and possibly contribute to hibernacula abandonment. Dyke et al. (2015) also state that frequent 

disturbance may cause females to drop young in the rearing process.

The extensive development of oil and natural gas within the Bakken Formation 

was mentioned specifically by Nelson et al. (2015) as altering habitat with no research 

on the effect on bats in the region. The LMNG and surrounding private lands are not 

protected from oil exploration and Nelson et al. (2015) encourages land managers to 

preserve important habitats in North Dakota such as the badlands, Turtle Mountains, 

Pembina Gorge, and forested riparian zones.

Summary

The northern long-eared bat is one of 11 bat species that occurs in North Dakota 

and is the only bat species that is listed as threatened under the Endangered Species 
54 USDA Forest Service RMRS-GTR-384. 2018.

Act. The northern long-eared bat is considered to be a seasonal resident in the State as 

hibernacula have not been found in North Dakota at this time. The top three predictive environmental variables used to model northern long-eared bat habitat suitability 

were: mosaic forest or shrubland (50–70 percent) / grassland (20–50 percent), max 

temperature of warmest month, and mean temperature of warmest quarter. Statewide 

surveys have been successful in identifying individuals in the LMNG along wooded 

riparian areas. The threats to this species include habitat loss and degradation as well as 

potential contamination associated with anthropogenic industrial activities, but research 

on the effects of these general threats is currently lacking. 
USDA Forest Service RMRS-GTR-384. 2018. 55

SECTION 5: ONGOING RESEARCH IN NORTH 

DAKOTA / OTHER RESOURCES

Multiple entities continue to conduct research on ecological impacts of oil and gas 

development on and around LMNG. Conversations with managers and scientists in the 

region reveal that the following groups are actively performing research.

U.S. Geological Survey (USGS)

The USGS Science Team About Energy and Plains and Potholes Environments 

(STEPPE) focused on brine contamination in the prairie pothole region to the northeast 

of LMNG and published a synthesis of their findings (Gleason and Tangen 2014). The 

USGS Northern Prairie Wildlife Research Center (NPWRC) has also been working 

on a synthesis of ecological concerns related to oil and gas development that is in the 

review process. Individual scientists at the USGS-NPWRC continue to work on examining the abundance of songbirds as driven by patterns of agricultural use and oil development (Max Post van der Burg) and avian response to road and well pad presence 

(Douglas Johnson).

U.S. Department of Agriculture–Agriculture

Research Station (ARS)

The USDA-ARS Northern Plains Agricultural Research Laboratory (NPARL) based 

in Sidney, Montana, has been researching changes in abundance and composition of 

vegetation, nematode, insect, and avian species on and near oil well pads. Additionally, 

Research Ecologist Erin Espeland continues to examine vegetation reclamation 

practices.

North Dakota State University

Multiple researchers at North Dakota State University are examining different 

aspects of the impacts of oil and gas development. Devan McGranahan’s lab has been 

quantifying the amount of road dust and examining its impact on the surrounding 

vegetation. Reclamation methods and directions have been examined for vegetation by 

Kevin Sedivec’s lab and for salt removal from soil by Aaron Daigh’s lab. Erin Gillam’s 

lab at North Dakota State University appears to be taking the lead on gathering information about the northern long-eared bat such as currently trying to identify any 

hibernacula that may exist in North Dakota. 
56 USDA Forest Service RMRS-GTR-384. 2018.

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