Much of the historic grassland ecosystem within Wyoming is still in a healthy condition, unlike grassland ecosystems of other areas. As a result, grassland species such as the swift fox (Vulpes velox), Burrowing Owl (Athene cunicularia hypugaea), and black-tailed prairie dog (Cynomys ludovicianus) are doing well in Wyoming. However, increasing pressures to recover natural resources and develop prairie habitat to accommodate an expanding population pose risks to the integrity of our natural systems. Wyoming is fortunate to have the opportunity to work with private landowners to conserve grasslands while they still exist across relatively large, intact landscapes. Additionally, Wyoming Game and Fish Department (WGFD) recognizes humans as essential components of the landscape, and the importance of maintaining responsible economic use of resources must be factored into our primary mission of conserving the state’s wildlife.

Grasslands comprise approximately 20 percent (19,600 square miles) of Wyoming's land area (Comer et al. 2003), primarily in the eastern half of the state (Figure 1). The majority of these grasslands occur in seven counties that contain more than 11 million acres of private land. Mixed-grass prairie and shortgrass prairie are the two grassland types found in Wyoming, with the former being much more abundant. Shortgrass prairie occurs mainly in the southeast corner of the state, and extends south into Colorado (Knight 1994). The dominance of buffalograss (Buchloe dactyloides) and blue grama (Bouteloua gracilis) indicates shortgrass prairie. Mixed-grass prairie is common across much of eastern Wyoming. Mixed-grass prairies typically receive more moisture and have greater plant species diversity. Common plant species include needle-and-thread (Stipa comata), western wheat-grass (Agropyron smithii), blue grama, sandberg blue grass (Poa sandbergii), prairie junegrass (Koeleria macrantha), and Indian ricegrass (Oryzopsis hymenoides).

  (Click map to enlarge)

Figure 1. Distribution of mixed-grass and shortgrass prairies on both private and public lands in Wyoming modified from Comer et al. (2003).

While the grasslands of Wyoming might appear at first glance to be relatively simple ecosystems, they support a great diversity of wildlife. Fifteen of the sixteen mammals and all nine bird species considered narrow endemics to the grasslands of the Great Plains (Samson and Knopf 1996) are found in Wyoming (Table 1). Many of Wyoming’s species of greatest conservation need (Table 2) are also found in grasslands (WGFD 2005a).
 

Table 1. Birds and mammals endemic to the grasslands of the Great Plains that are also present in Wyoming (Samson and Knopf 1996).

Species	Scientific Name	Habitat Affinity
Baird’s sparrow	Ammodramus bairdii	Widespread
Cassin’s sparrow	Aimophila cassinii	Shortgrass prairie
Chestnut-collared longspur	Calcarius ornatus	Short/mixed-grass prairie
Ferruginous hawk	Buteo regalis	Widespread
Lark bunting	Calamospiza melanocorys	Short/mixed-grass prairie
Long-billed curlew	Numenius americanus	Shortgrass prairie
McCown’s longspur	Calcarius mccownii	Shortgrass prairie
Mountain plover	Charadrius montanus	Shortgrass prairie
Sprague’s pipit	Anthus spragueii	Mixed-tallgrass prairie
Black-footed ferret	Mustela nigripes	Short/mixed-grass prairie
Black-tailed prairie dog	Cynomys ludovicianus	Short/mixed-grass prairie
Hispid pocket mouse	Chaetodipus hispidus	Short/mixed-grass prairie
Northern grasshopper mouse	Onychomys leucogaster	Short/mixed-grass prairie
Olive-backed pocket mouse	Perognathus fasciatus	Short/mixed-grass prairie
Plains harvest mouse	Reithrodontomys montanus	Short/mixed-grass prairie
Plains pocket gopher	Geomys bursarius	Widespread
Plains pocket mouse	Perognathus flavescens	Short/mixed-grass prairie
Prairie vole	Microtus ochrogaster	Mixed-grass prairie
Pronghorn	Antilocapra americana	Short/mixed-grass prairie
Swift fox	Vulpes velox	Short/mixed-grass prairie
Thirteen-lined ground squirrel	Spermophilus tridecemlineatus	Widespread
Western spotted skunk	Spilogale gracilis	Widespread
White-tailed jack rabbit	Lepus townsendii	Short/mixed-grass prairie

Table 2. Grassland ecosystem species of greatest conservation need in Wyoming (WGFD 2005a).  

Common Name	Scientific Name	Native Species Status
Bobolink	Dolichonyx oryzivorus	NSS4
Burrowing Owl	Athene cunicularia	NSS4
Chestnut-collared Longspur	Calcarius ornatus	NSS4
Sharp-tailed Grouse	Tympanuchus phasianellus	NSS3
Dickcissel	Spiza americana	NSS4
Ferruginous Hawk	Buteo regalis	NSS3
Grasshopper Sparrow	Ammodramus savannarum	NSS4
Lark Bunting	Calamospiza melanocorys	NSS4
Long-billed Curlew	Numenius americanus	NSS3
McCown's Longspur	Calcarius mccownii	NSS4
Mountain Plover	Charadrius montanus	NSS4
Short-eared Owl	Asio flammeus	NSS4
Black-footed ferret	Mustela nigripes	NSS1
Black-tailed prairie dog	Cynomys ludovicianus	NSS3
Hispid pocket mouse	Chaetodipus hispidus	NSS3
Olive-backed pocket mouse	Perognathus fasciatus	NSS3
Plains harvest mouse	Reithrodontomys montanus	NSS3
Plains pocket gopher	Geomys bursarius	NSS4
Plains pocket mouse	Perognathus flavescens	NSS3
Prairie vole	Microtus ochrogaster	NSS3
Swift fox	Vulpes velox	NSS4
Upland Sandpiper	Bartramia longicauda	NSS4
White-tailed prairie dog	Cynomys leucurus	NSS4

Of all the animals endemic to the grasslands, the black-tailed prairie dog is especially important due to its role as a keystone species and its dominating influence on the composition of grassland communities (Ricklefs 1993, Kotliar et al. 1999, Kotliar 2000). Through the actions of creating burrows and cropping the vegetation within a colony, black-tailed prairie dogs alter vegetation composition, create open habitat and fire breaks, modify soil conditions, affect energy and nutrient cycles, and create burrows that are used by a host of other animals including Burrowing Owls, black-footed ferrets (Mustela nigripes), long-tailed weasels (Mustela frenata), Mountain Plovers (Charadrius montanus), and swift foxes (Samson and Knopf 1996, Kotliar et al. 1999). The black-tailed prairie dog is also an important prey species of the black-footed ferret, Ferruginous Hawk (Buteo regalis), Golden Eagle (Aquila chrysaetos) and other predators.

Burrowing owls use the abundant and widely distributed prairie dog burrows as nest sites, and most of the Burrowing Owl breeding records in Wyoming are associated with prairie dog colonies. Prairie dog burrows also provide habitat for Burrowing Owl prey such as northern grasshopper mice (Onychomys leucogaster), tiger salamanders (Ambystoma tigrinum) and beetles. Prairie dog colonies provide short vegetation habitat required by Mountain Plovers for foraging and predator avoidance. Five of the six major concentrations of Mountain Plovers in Wyoming are associated with prairie dog colonies.

In contrast, other grassland species, such as the Upland Sandpiper (Bartramia longicauda) require habitat characteristics with greater residual cover, moderate to high litter cover and little bare ground. Such differences in habitat requirements emphasize the need to manage grasslands for diversity and to recognize the ecological potential of different sites or situations. Examples of other grassland-associated species included in the SGCN list and likely to parallel the response of Upland Sandpipers to conservation efforts include the Sharp-tailed Grouse (Tympanuchus phasianellus), Baird's Sparrow (Ammodramus bairdii), and Sprague's Pipit (Anthus spragueii). These species all show strong affinities for native grasses and heterogeneity of ground cover and vegetation height, while avoiding areas dominated by exotic plants or monocultures (WGFD 2005a).

Historically, the estimated 30–60 million bison that roamed the Great Plains influenced the prairie by grazing some areas intensively and creating patches of open habitat that differed from other areas of prairie with temporary low use (Samson and Knopf 1996). Thus, bison contributed to habitat diversity by creating a shifting mosaic across the landscape. Livestock and grazing systems that are regulated by fences have replaced free-ranging bison, and grassland habitats now occur in a more homogeneous state. However, innovative livestock producers and grazing systems with domestic livestock offer an opportunity to create and maintain desired plant conditions that may benefit wildlife and the long-term economic needs of producers.

Another recent influence on grassland habitat characteristics is the control of wildfires. Historically, fires in the Great Plains occurred at intervals of approximately 2–25 years (Wright and Bailey 1980). Wyoming grasslands are arid and probably burned less frequently than the more mesic grasslands of the Great Plains because they do not quickly accumulate the fine fuels necessary to carry fire (Knight 1994). Additionally, reduced fuel loads caused by intensive bison grazing and wallowing (Knapp et al. 1999) and prairie dog colonies (Kotliar et al. 1999) further altered fire intensity, frequency and burn patterns. Burning, especially in taller grasslands, removes the insulating detritus, thereby allowing the soil to warm up sooner and plants to grow earlier in the spring, when water is available. Alternatively, water stress can be aggravated by fire if moisture that would have been used for plant growth during the short growing season evaporates from the warmer, blackened soil surface (Knight 1994). Thus, net primary productivity could increase or decrease depending on the circumstances. Grassland ecosystems are well adapted to disturbance events, such as fire and grazing, which created a mosaic of habitat diversity across the landscape. However, fire regimes have been altered due to the adoption of fire suppression as a guiding principle for land management during the past century. Complete fire suppression can result in accumulation of mulch and conditions that favor cool-season exotic species, and it most likely accounts for the active invasion of woody plants in the southern portion of the northern mixed prairie (Samson and Knopf 1996).

More recently, resource extraction has influenced the grassland ecosystem. Wyoming produces 35% of the nation’s coal (Wyoming Mining Association 2004), 96% of which originates in northeastern Wyoming grasslands (Campbell, Converse and Sheridan Counties) (Lyman and Jones 2005). Coalbed natural gas development is also occurring in large portions of Wyoming’s grasslands, with most of the current activity in northeastern Wyoming. An estimated 12,000 wells were developed within the Powder River Basin by 2003 (Bureau of Land Management 2003). The Bureau of Land Management (BLM) forecasts that another 39,000 CBNG wells may be developed in the Powder River Basin Environmental Impact Statement area over the next 10 years (BLM 2003).

Noxious and invasive plants may be the biggest threat and most significant conservation issue for grassland ecosystems. Weeds that have altered the composition of native grassland flora in Wyoming include Canada thistle (Cirsium arvense), leafy spurge (Euphorbia esula), Russian knapweed (Acroptilon repens), spotted knapweed (Centaurea maculosa), saltcedar (Tamarix gallica), and cheatgrass (Bromus tectorum). For example, the Wyoming Cooperative Weed and Pest Survey data at the University of Wyoming shows cheatgrass increasing in 18 of 23 counties in the state. Noxious and invasive plants can be very aggressive and can dominate plant communities. When this happens, they reduce the diversity of the native plant community and, in turn, reduce the food items and cover diversity that native wildlife have adapted to over thousands of years.

Urbanization is also impacting parts of eastern Wyoming, where the population has increased 160% between 1970 and 2000 (Wyoming Department of Administration and Information). Urban sprawl causes direct habitat loss and fragmentation of grasslands across Wyoming.

Proposed Conservation Actions

Increasing grassland heterogeneity and maintaining or establishing natural disturbance patterns will ensure a positive future for Wyoming’s grassland species, ranchers, and farmers. Some basic conservation goals include:

1.         Increase grassland heterogeneity by:

a.       introducing fire back into grassland systems via patch burning plans;

b.      encouraging grazing strategies that also favor habitats for native vegetation and sensitive wildlife species; and

c.       introducing disturbance via mechanical treatments.

2.         Develop cooperative agreements with willing landowners to prevent habitat fragmentation and conversion in those grassland habitats that are integral for maintaining grassland habitat diversity and grassland-obligate wildlife species.

3.         Continue cooperative efforts to control noxious and invasive plants, especially cheatgrass, in the Thunder Basin National Grasslands region and the rest of eastern Wyoming.

4.         Reseed native grasses and forbs.

5.         Develop forage reserve management agreements to provide relief to sensitive grassland communities. This may include, but is not limited to, assisting livestock operators with moving grazing to other areas during times when private land habitat improvement projects are being implemented and/or from areas affected by wildfires, droughts or other natural events to enhance or speed grassland habitat recovery.

6.         Where possible, implement best management practices detailed within the Wyoming Game and Fish Commission document Recommendations for development of oil and gas resources within crucial and important wildlife habitats (WGFD 2004).

7.         Where possible, implement best management practices detailed within the Wyoming Game and Fish Commission document A plan for bird and mammal species of greatest conservation need in Eastern Wyoming grasslands (WGFD 2005b).

Grassland projects will focus on landscapes with a high density of native prairie remnants, areas with multiple or dense concentrations of at-risk animal and plant species, and areas with unique or extremely high-quality plant communities. These areas include the mixed-grass prairies in the Laramie Basin, Shirley Basin, Thunder Basin National Grasslands, and the Sheridan region, short-grass prairie in southeastern Wyoming, and several areas where there are extensive prairie dog complexes.

Expected Results and Benefits

Conducting prescribed burns and implementing grazing strategies will increase grassland heterogeneity and improve habitats for native vegetation and sensitive wildlife species. These practices will benefit the Upland Sandpiper by increasing residual native grasses for nesting and insect production for brood rearing and the swift fox by increasing small mammal and avian diversity and abundance. Securing permanent conservation easements will maintain open spaces, maintain intact habitats, and prevent habitat fragmentation and conversion in those grassland habitats that are integral to maintaining grassland habitat diversity and grassland-obligate wildlife species into the future. Developing forage reserve agreements will accelerate grassland habitat recovery. All of these activities maintain or increase black-tailed prairie dog, swift fox and Upland Sandpiper populations in grassland ecosystems and will benefit other grassland species such as the:

Long-billed Curlew;

Chestnut-collared Longspur  (Calcarius ornatus);

Lark Bunting (Calamospiza melanocorys);

McCown's Longspur (Calcarius mccownii);

Mountain Plover;

Bobolink  (Dolichonyx oryzivorus);
Dickcissel  (Spiza americana);

Grasshopper Sparrow (Ammodramus savannarum);

Short-eared Owl (Asio flammeus);

Sharp-tailed Grouse;

white-tailed prairie dog (Cynomys leucurus);

hispid pocket mouse (Chaetodipus hispidus);

olive-backed pocket mouse (Perognathus fasciatus);

plains harvest mouse (Reithrodontomys montanus);

plains pocket mouse (Perognathus flavescens);

prairie vole (Microtus ochrogaster); and

plains pocket gopher (Geomys bursarius).

Additional Information

Grassland Best Management Practices

A Plan for Bird and Mammal Species of Greatest Conservation Need in Eastern Wyoming Grasslands

Strategic Habitat Plan

Recommendations for development of oil and gas resources within crucial and important wildlife habitats

Comprehensive Wildlife Conservation Strategy

Literature Cited

Bureau of Land Management. 2003. The record of decision and resource management plan amendments for the Powder River Basin oil and gas project of land management. U.S. Department of Interior, Bureau of Land Management, Buffalo, Wyoming.

Comer, P., D. Faber-Langendoen, R. Evans, S. Gawler, C. Josse, G. Kittel, S. Menard, M. Pyne, M. Reid, K. Schulz, K. Snow, and J. Teague. 2003. Ecological systems of the United States: a working classification of U.S. terrestrial systems. NatureServe, Arlington, Virginia. Online: http://www.natureserve.org/publications/usEcologicalsystems.jsp

Knapp, A. K., J. M. Blair, J. M. Briggs, S. L. Collins, D. C. Hartnett, L. C. Johnson, and E. G. Towne. 1999. The keystone role of bison in North American tallgrass prairie: bison increase habitat heterogeneity and alter a broad array of plant, community, and ecosystem processes. Bioscience 49:39–50.

Knight, D. L. 1994. Mountains and plains, the ecology of Wyoming landscapes. Yale University Press, New Haven, Connecticut.

Kotliar, N. B. 2000. Application of the new keystone-species concept to prairie dogs: how well does it work? Conservation Biology 14:1715–1721.  

Kotliar, N. B., B. W. Baker, A. D. Whicker, and G. Plumb. 1999. A critical review of assumptions about the prairie dog as a keystone species. Environmental Management 24:177–192.

Lyman, R. M., and N. R. Jones. 2005. Wyoming minerals update: coal. October 2005. Wyoming State Geological Survey, Laramie, Wyoming. Online: http://www.wsgs.uwyo.edu/Mineral_Updates/Oct2005/MU_Coal_Oct2005.pdf

Ricklefs, R. E., editor. 1993. The economy of nature. Third edition. W.H. Freeman and Co., New York, New York.

Samson, F. B. and F. L. Knopf. 1996. Prairie conservation: preserving North America’s most endangered ecosystem. Island Press, Washington, D.C.

Wright, H. A., and A. W. Bailey. 1980. Fire ecology and prescribed burning in the Great Plains: A research review. U.S. Forest Service, General Technical Report. INT-77, Washington D.C.

 Wyoming Department of Administration and Information. 2001. Historical decennial census population for Wyoming counties, cities, and towns. Wyoming Department of Administration and Information, Division of Economic Analysis, Cheyenne, Wyoming. Online: http://eadiv.state.wy.us/demog_data/cntycity_hist.htm

Wyoming Game and Fish Department. 2004. Recommendations for development of oil and gas resources within crucial and important wildlife habitats. Wyoming Game and Fish Department, Cheyenne, Wyoming.

Wyoming Game and Fish Department. 2005a. A comprehensive wildlife conservation strategy for Wyoming. Wyoming Game and Fish Department, Cheyenne, Wyoming.

Wyoming Game and Fish Department. 2005b. A plan for bird and mammal species of greatest conservation need in Eastern Wyoming grasslands. Wyoming Game and Fish Department, Cheyenne, Wyoming.

Wyoming Mining Association. 2004. A concise guide to Wyoming coal. Wyoming Coal Information Committee, Wyoming Mining Association, Cheyenne, Wyoming.