Grazing Management Practices

Livestock producers in the Intermountain West try to meet the nutritional requirements of animals by using seasonal ranges when environmental conditions are most conducive and forage quantity and quality are as high as possible. Low-elevation desert shrub ranges, when available, are used in winter (early November to mid-April), mid-elevation foothill ranges are used in the spring (mid-April to early July) and occasionally in the fall (early October to early November), and high-elevation mountain ranges are used during summer and early fall (early July to early October). In general, forage “bottlenecks” occur during winter and in early spring when plant growth is limited on sagebrush steppe and sagebrush shrublands, and hay must be fed sparingly to reduce costs. Spring grazing on these foothill ranges is a critical period in the livestock management cycle, i.e. the high nutritional demands of cows that calve in March must be met so calves receive enough milk for rapid growth and cows are physiologically ready for rebreeding in June or July. The slow growth of native perennial grasses in early spring is often inadequate for lactating cows. And, as the season progresses, native grasses grow rapidly for a short time, but forage quantity and quality decrease as plants mature. With the dominant native grasses on foothill ranges being satisfactory only from early May to mid-June, other seeded forages, primarily introduced grasses such crested wheatgrass and Russian wildrye (Psathyrostachys juncea), are often used during April and later in the summer before cattle are moved to mountain ranges. If livestock are not properly managed, overgrazing is likely to occur on foothill ranges at this time.

Good grazing management is based on several principles, including: proper stocking rates and grazing intensity, proper kind(s) of grazing animal(s), proper season of grazing, and proper distribution of animals. Selection of the appropriate stocking rate is the most important of all grazing management decisions from the standpoint of vegetation, livestock, and economic return, regardless of the grazing system used. When light, moderate, and heavy stocking rates were used in combination with four grazing systems on seeded foothill range in central Utah, heavy stocking resulted in the lowest daily animal gains, a decline in forage production, little or no seed production, excessive trampling of plants and soil, and accelerated invasion of undesirable shrubs and exotic annual weeds. Light stocking essentially left the most forage for fall grazing. Moderate stocking resulted in the most favorable combination of forage yield, animal performance, availability of forage for fall grazing, and resistance to shrub reinvasion. Similar results have been reported for grazing systems using light, heavy, and moderate stocking rates on native sagebrush-grass ranges. Cattle are the primary grazers in sagebrush ecosystems, and can damage bunchgrasses during the flowering period, so plants should be grazed earlier in the spring and be allowed to complete seed set every second year. Heavy and even moderate stocking of sheep in the spring can damage actively growing perennial forbs; however, sheep consume sagebrush and don’t utilize dormant herbaceous species when grazing in late fall, allowing forbs to increase. Managers can improve the distribution of livestock on sagebrush-grass ranges by developing additional water sources, fencing, strategically placing salt and/or low-moisture molasses blocks, providing shade and windbreaks, developing trails on steeper slopes, and improving forage quality/quantity through burning or seeding.

Climate, topography, life history traits of key forage species, livestock performance, wildlife needs, watershed protection, ease and cost of implementation and operation, and flexibility under changing conditions are important considerations involved in grazing system selection. Common grazing systems that have been used in sagebrush steppe and sagebrush shrublands include: 1) continuous or season-long grazing, where livestock are allowed free access to any part of a range throughout the grazing season, and use follows the same general pattern each year; 2) deferred-rotation grazing, which involves rotating the deferment (delay of grazing during the growing season) of typically three pastures each successive year to promote plant reproduction and improve vigor; and 3) rest-rotation grazing, which involves rotating the rest (full year of nonuse) of typically four pastures each successive year to give plants a longer period to recover from past grazing influences. Time-controlled grazing systems have been used to a limited extent, and include: 1) short duration grazing, where very short periods of intensive grazing (1-3 days) are followed by short non-used periods (2-3 weeks) in several pastures during the grazing season; and 2) high-intensity low-frequency grazing, where short periods of intensive grazing (7-10 days) are followed by long rest periods (≥ 1 year) in numerous pastures. Research has shown that specialized grazing systems generally give either modest or no increase in grazing capacity, animal performance, and financial returns over continuous or season-long grazing, particularly when animals are well-distributed at a moderate stocking rate.

There is not one best grazing system that can be applied across sagebrush ecosystems. Deferred-rotation, rest-rotation, and high-intensity low-frequency systems have traditionally been viewed as conservation practices favoring native perennial grasses. However, periods of complete rest or deferment until seed set can also favor cheatgrass as much as or more than perennial grasses when it is present in pastures. Rest-rotation and high-intensity low-frequency systems, with their extended rest periods, integrate well with wildlife use (i.e., nesting, rearing of young) and facilitate the implementation of vegetation management treatments (i.e., burning, chemical and mechanical treatments, seeding). Short-duration grazing systems have not been widely used on sagebrush-grass ranges because the relatively short growing season (60-90 days), small size of most ranches [800-1,200 ha (2,000-3,000 ac)], and fencing costs don’t make it a viable option. One example where high-intensity low-frequency grazing has been successful in predominantly sagebrush-grass rangeland is on a 81,000 ha (200,000 ac) ranch in northern Utah that supports 5,000 cattle, 3,000 sheep, and abundant wildlife species on 60+ large pastures. The managers of this large ranch have the flexibility to view livestock grazing schedules and stocking rates as variables to be integrated adaptively with other management practices to meet several objectives, including livestock production, wildlife abundance and diversity, recreation, and land health.

Vegetation Management

Several manipulation practices have been used to modify sagebrush steppe and sagebrush shrubland communities to meet management objectives, which include improved forage production for livestock, enhanced habitat for wildlife, control of invasive species, and restoration/rehabilitation of areas that have been disturbed by wildfires, cultivation, and energy and mineral development. Management practices can be grouped into five general categories (prescribed fire, mechanical, chemical, biological, and revegetation), and they are often integrated in an attempt to reach management objectives.

Livestock Forage Production

A common problem in degraded sagebrush steppe and sagebrush shrubland communities is the increase in density, cover, and size of sagebrush and other shrubs and the concomitant decrease in perennial grasses and forbs, i.e., livestock forage. If degradation has not progressed very far, it may be possible to use previously described rotational grazing systems to gradually improve forage production and grazing capacity. When degradation has progressed too far, manipulation practices (prescribed burning, herbicide application, mechanical treatments), often followed by revegetation, will be necessary to reduce sagebrush dominance and increase herbaceous forage species. The suitability of a particular practice depends upon a variety of factors, including the density, height, and age of sagebrush and other shrubs, the amount and kinds of grasses and forbs in the understory, the topography and rockiness of the area, the type of soil and it’s susceptibility to erosion, the size of the area to be treated, the availability of equipment, and treatment costs. During the first 5-6 years after treatment, big sagebrush control can increase forage production 2-3-fold compared to untreated areas; however, follow-up treatments will probably be required at intervals of ≤ 20 years, since sagebrush can recover after manipulation under most conditions.

Prescribed burning can be successful when there are sufficient perennial grasses and forbs to provide understory fuels to carry the fire and to respond to increased resource availability and the lack of sagebrush competition after the fire. Big sagebrush does not resprout following fire, allowing several years of increased forage production before it reenters and gradually regains control of the community. If present, other shrubs such as rabbitbrushes and horsebrush resprout from basal stem buds, increasing in abundance after fire, and may require a follow-up herbicide treatment. Burning is usually done in the fall when fine fuels (dormant perennial grasses and forbs) and sagebrush canopies are drier and environmental conditions (air temperature, relative humidity, and wind) are more suitable for carrying a fire. During the spring, there are fewer days with favorable environmental conditions for burning, and increased fuel moisture usually limits burn size. Burned areas are typically rested from livestock grazing for at least one growing season after treatment.

Selective herbicides have been used for decades to control sagebrush and other shrubs and release perennial grasses (from competition) to increase forage production. 2,4-D, a translocated, growth-regulator herbicide, has generally been the most effective and economical chemical for sagebrush control. Aerially application of 2,4-D in late spring, near the end of the effective spraying period for sagebrush, will also control some associated rabbitbrush plants. Though this selective herbicide does not damage perennial grasses, it can severely damage perennial forbs such as arrowleaf balsamroot and milkvetch (Astragalus stenophyllus), which are important forage species. Thus, sites should be assessed for species composition before spraying to determine the extent of damage that may occur, and if seeding may be necessary to increase forage production and discourage replacement by undesirable species. Sprayed areas are usually rested from livestock grazing for at least the remainder of the year in which they are sprayed.

Several mechanical methods are available for controlling sagebrush and increasing herbaceous forage production. Sagebrush plants can be cut off near the base with a heavy-duty mower, broken off or uprooted with a pipe harrow, and crushed with an aerator (large rolling cylinder), causing limited disturbance to desirable understory species (Figure 26). Two passes with a pipe harrow or aerator will be required for a higher level of sagebrush control. If needed, forage species can be seeded at the time of the treatment. Where there is not an adequate understory of desirable perennial grasses and forbs, plowing or disking will kill sagebrush and prepare a seedbed for revegetation. Mechanical treatments are typically implemented in the fall, and livestock are usually excluded from treated areas the following growing season.

Revegetation is necessary when perennial grasses and forbs are lacking, or when a manager chooses to plant improved forage species. Drill seeders with multiple seed boxes and metering devices, and depth bands on disks, can dispense multiple species with varying seed sizes and shapes and seeding depth requirements. Ground broadcast seeding can be coupled with mechanical treatments, and is often used to seed areas that are inappropriate for drill seeding, such as rocky, rough, or steep terrain, areas with large amounts of debris, and small, irregularly shaped areas. Aerial broadcast seeding with aircraft is used to distribute seeds over large areas. Early efforts in the 1950s and 1960s were oriented toward establishing productive, monotypic stands of introduced, perennial grasses such as crested wheatgrass, intermediate wheatgrass (Thinopyrum intermedium), and Russian wildrye. Since then more emphasis has been given to mixtures of perennial herbaceous species that provide livestock forage and enhance wildlife habitat. Seedings are most often conducted in the fall, and livestock are excluded from seeded areas for two growing seasons.

Poisonous Plants

Many poisonous plants are toxic at all times, whereas others are toxic only under certain conditions. Careful managers can reduce the risk of livestock poisoning and even allow some poisonous plants to be used as nutritious forage at select times. The following management practices can help protect livestock from poisoning: 1) learn to identify poisonous plants and the conditions under which they can be dangerous to livestock; 2) develop a grazing plan to improve rangeland and prevent poisoning; 3) do not allow stressed or hungry animals to graze in areas infested with poisonous plants; 4) provide adequate water for livestock; 5) be especially careful when grazing animals unfamiliar to an area; 6) train animals to avoid poisonous plants by implementing conditioned-taste aversions where animals associate the taste of the plant with the stomach illness caused by an administered drug (lithium chloride); and 7) control poisonous plants with herbicides and other manipulation treatments where feasible.

A change in grazing management significantly reduced cattle losses to white locoweed (Oxytropis sericea) at a high elevation sagebrush area in northern Utah. For many years, ranchers used a rest rotation grazing system, with 3 pastures grazed in sequence, and 1 pasture rested each summer. Range condition improved, but annual losses to locoweed exceeded 20%. Based on observations that most consumption of locoweed occurred after flowering during August, the grazing season was reduced from 71 to 47 days, cattle numbers were increased, and the grazing method was changed to a 3-herd, 4 pasture system. Most of the highly toxic young fruit pods were avoided, and yearly losses to locoweed poisoning declined to about 3%.

After mature broom snakeweed plants in sagebrush and other semiarid plant communities are killed by herbicides, prescribed burning or targeted grazing, snakeweed seedlings have difficulty establishing in the presence of established cool-season, perennial grasses due to resource competition. If perennial grasses are not abundant following snakeweed control, species such as crested wheatgrass should be seeded in an attempt to develop a grass stand that will prevent snakeweed establishment.

Cultivation

Ecological processes involved in the natural restoration of abandoned cultivated lands in sagebrush ecosystems may take over a century to recover on their own, and many historically dry-farmed sites can be altered to the point that the potential natural vegetation state is no longer attainable. However, since the passage of the 1985 Farm Bill, millions of hectares of actively cultivated lands in sagebrush steppe and sagebrush shrubland areas in the Intermountain West have been planted to perennial grasses, forbs, and shrubs under the Conservation Reserve Program (CRP). This voluntary program, administered by the U.S. Department of Agriculture, allows farmers to take agricultural lands (particularly environmentally sensitive lands) out of production for 10-15 years to achieve conservation objectives, including reduced soil erosion and improvement of wildlife habitat. The program provides the farmers with annual rental payments for non-use and cost-share assistance (up to 50%) for approved conservation practices. A recent study in eastern Washington found that CRP fields were used by a variety of passerine birds, and they were important as nesting, brood-rearing, and wintering habitat for sage-grouse.

Invasive Species and Wildfires

Invasive plants by themselves, and especially when they alter fire regimes, create complex management problems in sagebrush and other arid and semiarid ecosystems. Many invasions have expanded to large landscape scales, and considerable environmental variability defines windows of management opportunities in space and time, which are more limited in lower elevation Wyoming big sagebrush communities than in higher elevation mountain big sagebrush communities. Thus, one of the main challenges for managers is to determine the ecosystem properties that define existing windows and/or determine how to create new windows of opportunity. This challenge has been addressed, in part, with the development of decision-making frameworks such as ecologically based invasive plant management (EBIPM), which identifies the causes of succession and associated ecological processes influencing invasion, uses ecological principles to link processes in need of repair with appropriate vegetation management strategies and tools, and provides a science-based method for adaptive management planning. EBIPM and similar integrated weed management approaches have improved the control of invasive forbs such as leafy spurge, diffuse knapweed (Centaurea diffusa) and spotted knapweed (Centaurea stoebe), and EBIPM has recently been implemented on cheatgrass-dominated rangelands. Since the management of invasive junipers in higher elevation sagebrush communities is covered in detail in a companion module, the focus here is on the management of invasive annual grasses in low- to mid-elevation sagebrush communities.

Management of sagebrush communities can take two forms: passive management for intact communities dominated by desirable species and active management for invaded communities dominated by exotic annual grasses. Passive management involves efforts to maintain or improve community resistance to invasion and reduce the propagule pressure of annual grasses. A common approach is to change livestock management, i.e. make adjustments in animal numbers, grazing seasons, duration of grazing, and/or distribution, in order to increase the diversity and abundance of desirable species, particularly perennial grasses. Moderate levels of livestock grazing can play an important role in reducing the risk and severity of wildfires by decreasing fine fuel loads and continuity. Reductions in the propagule pressure of annual grasses can be accomplished in different ways. When crested wheatgrass was established as a vegetation barrier at the interface of medusahead infestations and sagebrush-grassland communities, the cover and density of medusahead were 42- and 47-fold less, respectively, in protected communities than in unprotected communities. The taller-statured crested wheatgrass plants reduced the spread of propagules by physically intercepting them, and increasing the distance medusahead plants had to disperse propagules to find suitable sites for establishment in adjacent sagebrush-grassland communities. Cheatgrass seed production can be reduced significantly when plants are intensively grazed just before emergence of the inflorescence, decreasing the potential for propagules to spread from an infested area to an adjacent sagebrush-grassland community.

Active management is undertaken when desired species or functional groups are absent or poorly represented in invaded communities. Annual grass-dominated areas can be modified with several practices in an attempt to reduce catastrophic wildfires, repair ecological processes, and improve ecosystem structure, function and productivity. These practices are most effective when sequenced appropriately in an integrated management approach. Control of medusahead and cheatgrass is greatest when prescribed burning in fall is closely followed by the application of imazapic, a preemergence herbicide. Burning removes annual grass litter that can intercept imazapic, allowing greater herbicide activity for killing fall-germinating cheatgrass and medusahead. Desirable species are usually drill seeded after imazapic application in late fall or early winter. Imazapic residual activity the following spring can injure developing seedlings of sagebrush and some seeded perennial grasses when the herbicide is applied at higher rates for better annual grass control. Even when annual grasses are successfully controlled and imazapic residual activity is not a problem, native species often fail to establish due to environmental conditions and annual grasses can rapidly reinvade. Thus, managers often use non-native revegetation species such as crested wheatgrass, Siberian wheatgrass (Agropyron fragile), Russian wildrye, and forage kochia (Kochia prostrata), which cost less, are more available, and have better establishment characteristics than most natives. When compared to native sagebrush communities, these simplified non-native communities provide limited habitat for wildlife, but there are no substantive differences in ecological processes, and they can be resistant to invasive species and resilient to fires. Seeding of native forbs, grasses and shrubs into established crested wheatgrass stands has not been successful to date; however, sagebrush seedlings have been transplanted and successfully established in crested wheatgrass stands. Efforts have been made to reduce management costs by burning and applying herbicide in areas that have remaining native vegetation and may not need revegetation, taking advantage of naturally occurring wildfires as burn treatments to be followed by herbicide application and seeding, and using a single-entry approach, where the herbicide and seeds are applied simultaneously.

Large, often catastrophic wildfires on public rangelands require stabilization within 1 year of containment to prevent resource degradation, and rehabilitation within 3 years of containment to repair or improve lands unlikely to recover naturally to management-approved conditions. Integrated approaches and native species are used whenever possible; however, treatment costs, equipment and seed availability, and topographic constraints can modify planning, e.g., eliminating herbicide application and using aerial broadcast seeding of mostly introduced species on large areas of rough terrain.

Active management practices have also been used to create fuel breaks to protect revegetated areas and intact sagebrush communities. When cheatgrass is intensively grazed by cattle just prior to emergence of the inflorescence in the spring, and 80-90% of the biomass is removed, there is a significant reduction in flame length and rate of fire spread during the subsequent fire season (Figure 28). Due to the short grazing window and large number of animals required, this treatment would be best applied in a strip instead of a large block. A longer-term fuel break can be created by green stripping, where flammable cheatgrass is replaced by vegetation that is less likely to ignite and carry a fire. Strips up to 100 m (325 ft) wide are either disked or treated with herbicide (glyphosate, imazapic) to control cheatgrass and then seeded with species that maintain a higher moisture content during the growing season, i.e., crested wheatgrass and forage kochia.

Energy and Mineral Development

The drastic disturbances associated with oil and gas development, and surface mining for coal, minerals, and metals require intensive reclamation practices to repair the damage to vegetation, soils, and hydrologic processes in sagebrush and other arid/semiarid rangeland ecosystems. The components of a successful surface mine reclamation plan include: 1) determining the pre-disturbance ecosystem functions that must be repaired following disturbance; 2) conducting a pre-disturbance inventory of vegetation, soil, topographic, hydrologic, wildlife, archeological, and historical resources; 3) salvaging, separating, and stockpiling soil; 4) backfilling, grading to original or approximate contour, redistributing salvaged soil, and preparing a seedbed; 5) revegetating with native or appropriate species; 6) managing for post-mining uses such as livestock grazing and/or wildlife habitat; and, 7) long-term monitoring for revegetation success, invasive weeds, erosion, wildlife diversity and abundance, and livestock production. There are similar components for oil and gas development reclamation plans; however, the disturbances for well pads and reserve pits are much smaller in size [< 1ha (1-2 ac.)] and distributed across landscapes [1 per 4-16 ha (10-40 ac.)] connected by a network of roads and pipelines. During interim reclamation, the reserve pit and portions of the well pad not needed for operational purposes are recontoured, topsoiled and revegetated; during final reclamation (following well plugging and abandonment), the well site and roads are recontoured, topsoiled, and revegetated.

Wildlife Habitat

As mentioned earlier, large-scale sagebrush treatments conducted from the 1950s through the 1970s were focused primarily on increasing forage production for livestock; however, in the last few decades, treatments have been increasingly applied to enhance habitat conditions for wildlife species using sagebrush habitats. Treatments are typically planned to emulate disturbances (i.e., wildfires, insects/pathogens) that maintain a mix of seral stages in a mosaic or patchy pattern with different age classes and canopy covers of sagebrush (and other shrubs) and a diversity of grasses and forbs. In addition to maintaining or improving existing sagebrush communities, efforts are also aimed at mitigating habitat losses due to fragmentation caused by land development, invasive species, and catastrophic fires. The management of sagebrush habitat for two important wildlife species, mule deer and the greater sage-grouse, is described below.

Management efforts for mule deer habitat have typically been directed toward protecting and enhancing sagebrush and other important browse species on winter ranges. These ranges are primarily limited by browse/forage quality and quantity due to the aging of native plants and the increase in abundance of undesirable plants. Thus, habitat improvement practices such as prescribed burning, mechanical treatments, herbicides, and seeding have been used to replace undesirable species with desirable species and to replace overly mature desirable plants with younger, more nutritious plants of the same species. Several small treated areas [2-10 ha (5-25 ac)] with irregular edges dispersed in a mosaic pattern within an untreated matrix of sagebrush provide a high edge-treated area ratio with nearby cover for security and thermal regulation. In drier, lower elevation Wyoming big sagebrush communities, managers should use extreme caution or not treat stands where cheatgrass or other invasive species are present. If Wyoming big sagebrush communities are treated, it is imperative to seed manipulated areas with a diverse seed mix to prevent/reduce weed invasion. Seeding is often recommended following treatments in more mesic, higher elevation, mountain big sagebrush communities.

Sage-grouse require a variety of plant communities across large landscapes for breeding, nesting, brood-rearing, and wintering. Sparsely vegetated areas (leks) are used for breeding. Nesting habitat should have 15-25% sagebrush canopy cover of medium height [40-80 cm (16-32 in)] and tall [> 18 cm (7.5 in)] bunchgrasses for screening cover. Brood-rearing habitat should have an abundance of forbs and insects, which are associated with lower shrub canopy cover (< 20%). Wintering habitat is comprised of medium height and taller sagebrush that remains 25-35 cm (10-14 in) above the snow on south and west facing slopes. Previously described threats resulting in the loss and fragmentation of sagebrush communities, and changes in the structure and composition of remaining communities have significantly altered these sage-grouse habitats, creating a complex management challenge at a regional scale. A landscape triage approach has been proposed for identifying and prioritizing lands for vegetation manipulation treatments. Lands are grouped into three categories – one that needs no immediate treatment, one that is significantly damaged and will not recover even with intervention, and one that is damaged but has the potential to recover with intervention – based on rangeland health assessments and state-and-transition models associated with ecological site descriptions. State-and-transition models also aid in determining if passive or active management should be used to achieve desirable habitat changes.

Passive management can be achieved by changing current management practices to promote the recovery of desired plant species or vegetation structure. Due to the prevalence of livestock grazing as a land use, changes in livestock management, i.e., kinds and numbers of animals, season of grazing, and/or duration of grazing, could positively impact large expanses of sage-grouse habitat. Switching from season-long to time-controlled (high-intensity low-frequency) cattle grazing, described earlier in the “Grazing Management” section, prevented an increase in shrub dominance and promoted an increase in herbaceous plant diversity and abundance, improving sage-grouse habitat in higher elevation Wyoming big sagebrush communities in northern Utah. Intensive sheep grazing in fall significantly reduced sagebrush cover and increased perennial forb and grass cover, improving brood-rearing habitat at a mountain big sagebrush site in south-central Utah.

Active management, using prescribed fire, chemical and mechanical treatments, and revegetation, is necessary when desirable species have been eliminated from sites or vegetation structure cannot be modified by passive management. These vegetation manipulation practices, described earlier in the Livestock Forage Production section, have advantages and disadvantages that should be considered before applying them to modify sage-grouse habitats. Prescribed fire should not be used where sagebrush cover is the limiting factor for sage-grouse, i.e., nesting and wintering habitats, or where introduced annuals have invaded sagebrush communities. Six years after burning a Wyoming big sagebrush area in southeastern Oregon, habitat cover was about 50% lower than the unburned control area because of the loss of sagebrush, there was no increase in the yield or nutritional quality of forb species, and there was a decrease in the abundance of insects. Based on concerns about reduced forb abundance following applications of 2,4-D to reduce sagebrush cover, emphasis has shifted to using tebuthiuron, a soil-applied herbicide that can selectively control sagebrush and increase grass and forb production when applied at low rates. Tebuthiuron effectively reduced shrub canopy cover and increased forb cover to meet recommended guidelines for sage-grouse brood-rearing habitat in a mountain sagebrush community in south-central Utah, as did a Dixie-harrow mechanical treatment. Prescribed fire, tebuthiuron and mechanical treatments, in conjunction with seeding, have reduced shrub cover and increased herbaceous species diversity and abundance, and enhanced sage-grouse habitat in higher elevation Wyoming big sagebrush communities in northern Utah. Most literature, however, indicates that habitat management programs that emphasize implementing these treatments in drier, low elevation Wyoming big sagebrush communities are not supported with respect to positive responses by sage-grouse habitats or populations.

Wild Horses

The management of wild horses (and burros) is unique compared to other large herbivores on western rangelands because of their morphological and physiological characteristics, and the policies enacted to protect them. Being cecal digesters, horses consume a wider variety and larger amount of forage species compared to ruminant digesters of equivalent body mass. Also, an elongated head, more flexible lips, and the presence of upper front incisors allows horses to remove vegetation more closely to the ground than cattle. Horses (and burros) are not managed in the same manner as traditional wildlife species, whose numbers are controlled by hunters and natural predators, or domestic livestock, which are more intensively managed by grazing permits and rotational grazing systems. Management has focused primarily on the periodic removal of animals to try to maintain a balance between horse (and burro) populations, rangeland health, and other uses. Removed animals that aren’t adopted by private individuals are placed in long-term pastures in Midwestern states for the remainder of their lives. The BLM is investigating the logistics and efficacy of administering a contraceptive agent, porcine zona pellucida, to mares that are captured and released back onto the range.

Motorized Recreation

Management challenges arise when values and perspectives of stakeholders concerning types of recreation and their impacts on the environment are very different. Federal and state agencies have attempted to manage OHV use through resource or travel management plans. Planning involves input and cooperation from interested stakeholders, as well as a variety of collaborative actions, including development and distribution of educational materials (signs, maps, brochures), recommendations for use limits and trail closures, volunteer patrols, and adopt-a-trail programs. Effective management is challenging because agencies typically do not receive enough funding for all planning actions, as well as for enforcement of regulations, repair of damaged resources and monitoring.