KBR Wild Horse and Burro Information Sheet


(Information and images courtesy of BLM, Billings Resource Area Office)

  Preliminary Draft for Implementation
of the Pryor Mountain Wild Horse Range (PMWHR)
Herd Management Plan; July 1996


Maintain a healthy, viable herd of wild horses on the PMWHR, exhibiting characteristics of historical value promoting heritage and wildness:

  1. phenotypic attributes (color and conformation), common to existing Pryor Mountain horses, and including a diversity of body colors and types typical of historical Spanish-type horses;

  2. genotypic attributes (blood proteins and antigens), common to existing Pryor Mountain horses, and maintaining sufficient diversity to prevent the expression of recessive genes or other potential inbreeding-related traits;

  3. natural social order (harem bands and dominance hierarchy), whereby critical and successful decision-making animals are maintained as integral members to help preserve the natural working integrity of the herd;

  4. successful response to ecological pressures (environmental, natural predators, humans), whereby animals demonstrating a natural ability to retain flesh and health under stress, produce healthy and viable foals, and demonstrate wariness towards potentially harmful situations are maintained as integral parts of a viable population.

DISCUSSION: The Pryor Mountain Wild Horse Range presents a unique opportunity for the observation and study, or simple viewing and appreciation of wild horses in a natural, diversified range setting. In addition, the provisional history and genetic characteristics of this population suggest early, Spanish-type ancestry. As such, historically-significant features of these animals should be maintained both to help promote our understanding and appreciation of wild horses, but also to preserve these attributes for generations to come.

PLANNED ACTION: Based on earlier projections of range carrying capacity, a minimum of 95 + 10% horses was established (1992 Revised Herd Management Plan) as the appropriate management level (AML) for the Pryor population. BLM is supporting current research (National Biological Service) to determine a minimum genetically viable population size for the Pryors, and compiling data on long-term population recruitment following natural disasters (Table 1). Results of these research efforts may suggest a future revision of the Herd Management Plan and establish an allowable range for population numbers.

Resulting population size should allow for preservation of a near-natural sex-ratio (50/50 to 60/40 in favor of females) and population age structure. Natural processes (such as births and deaths), and population structure (pertaining to social groups and mating choice), comprise the working integrity of the herd and will be preserved as much as possible. In the interests of successful and minimally-intrusive management, however, immunocontraceptive techniques may be considered in the future (see goal #3).

Accurate censusing (ground-truthing and aerial surveys) and identification of all horses within the herd will take place on an annual basis. Due to the level of effort necessary to accomplish this task, volunteer support from the public and/or students will be sought out and highly encouraged. Currently, an exemplary database (including photo-records of all possible horses), is in the formative stages, compiling information from National Biological Service researchers, BLM employees and volunteers and members of the local public. Upon completion, copies of this database will be available from the Billings Resource Area office upon request. Efforts are also being made to document historical phenotype of these horses and members of the public with photographs and/or information are invited to participate.

Four scientifically-based attributes (listed above) will be evaluated and scored for each individual horse, and re-evaluated on an annual basis. In each case, data will be invited and incorporated from scientific researchers with expertise in each of these areas. Future genetic blood sampling, however, will be restricted only to those animals being prepared and restrained for adoption procedures. Selection lists, identifying potentially excisable animals, will be developed in advance of culling efforts. Opportunities will exist for fair public comment on culling choices. Given the popularity of the Pryor horses for public adoption, culling criteria will not emphasize desirability for adoption.

In order to solicit public participation in the long-term protection of the Pryor horses, panels will be placed on several existing administrative signs, during the summer of 1996, with the verbiage:

phone 406-238-1540

With additional support from special interest groups, volunteers and researchers, the BLM will continue to monitor public activity on the Pryors, in an ongoing effort to balance management and/or law enforcement visibility with critical use periods.


Establish and maintain a healthy, viable range in balance with the annual horse population and other wildlife. Given the multiple purposes of the range, (primarily the protection and management of horses, but also other wildlife, wilderness, watershed, recreation, etc), range monitoring, will include, but may not be limited to:

  1. horse migratory activity and seasonal range (actual) use, to determine predictable patterns and identify areas of potential over and/or under utilization by the horses. Other wildlife use will also be incorporated into this analysis.

  2. assessment of range health, in terms of vegetative quality and quantity, with an emphasis on comparing and contrasting areas representing different use levels by the horses.

  3. evaluation of the need for range expansion efforts, providing that additional acreage would be both available to and used by the horses at appropriate times of the year. Evidence is needed that any areas under consideration, must have been occupied by horses prior to 1971, in keeping with the Wild Free-Roaming Horse and Burro Act. These efforts may be necessary to ensure sufficient range to support a genetically viable population size.

DISCUSSION: Appropriate range monitoring procedures and schedules are critical to permit sound management decisions pertaining to range health within the PMWHR. Improved actual use, utilization, and vegetative monitoring will enhance the current study site database. Results and recommendations from current research efforts (Montana State University and Colorado State University), should help facilitate a sound risk-assessment approach. As much of the Pryor range encompasses low precipitation zones featuring slow vegetative response, it is important that all monitoring studies are designed for consistency and repeatability over the long-term.

Horses on the PMWHR demonstrate the propensity to naturally segregate into three geographically distinct herd areas - Burnt Timber Ridge, Sykes Ridge and the Park Service Dryhead area. During some years, however, significant mixing and sharing of mares and social groups may occur between different areas. Although there is an estimated total of 38,014 acres available to the horses, currently producing -1400 horse AUMS, Pryor horses demonstrate seasonal activity which actually restricts optimal use of the entire available area. Regular and recurrent monitoring will help elucidate activity and use patterns particular to specific social groups of horses.

If range areas can be identified which the horses are consistently avoiding or under-utilizing, this information must be incorporated into management decisions. If range areas are identified which the horses are consistently using on a trespass basis, then management must correct the situation or consider range expansion efforts where feasible.

PLANNED ACTION: During the summer of 1996, experienced BLM range conservationists, and National Biological Service and university researchers, will be contacted to review and comment on proposed monitoring programs. The long-term intent is to digitize this information using a GIS database system. Efforts will also be initiated to document an administrative history of the range with an emphasis on historical distribution of horses in the Pryors and surrounding areas. Public assistance is needed and encouraged with this documentation effort.

  1. Actual Use: Actual use is determined by counting and mapping presence of all social groups/horses on the range at various times of the calendar year. From this data, key-use areas can be identified, and the range can be stratified into seasonal use patterns. Animal health, condition factors, and physiological condition will be evaluated during this monitoring. In addition, fecal material can be collected from targeted animals and social groups to evaluate micro-histological composition and internal parasite count. Due to the level of effort necessary to accomplish this task, volunteer support from the public and/or students will be sought out and highly encouraged.

  2. Utilization: Vegetative 100-point utilization transects (Key Forage Plant Method), with accompanying photographs, will be performed within pre-determined key-use areas on a semi-annual schedule (spring and fall). Grazing cages and enclosures will reveal the productive potential of these areas under protected conditions as well as grazing impact. These data will provide the most accurate information regarding the degree of utilization and remaining available forage in key areas. Throughout the field season, additional utilization transects may also be performed at other points on the range. This will help to identify possible horse preferences based on environmental slope and aspect, and soil and forage type. This information will help to elucidate and possibly explain under-utilized range areas and forage.

  3. Range Health: These studies will be conducted on pre established sites located throughout the horse range. Evaluation of Daubenmire plots will be replicated on a three to five year interval, primarily during the early summer(May-June) field season. These efforts will yield information on plant species lists and potential and current plant productivity. There is long-term value in this type of study, especially if efforts are consistent and repetitive over many (>20) years


Target a strategy of humane (limited stress-inducing) and minimum, cost-effective management in keeping with the 1971 Wild Free-Roaming Horse and Burro Act. Emphasize a whole herd focus, wherein management decisions prioritize long-term population viability, not necessarily individual animal retention. Maintain a population number which:

  1. ensures genetic viability of the population;

  2. exists in balance with multiple uses and sustained range health;

  3. provides a suitable buffer against potential natural disaster; and

  4. provides sufficient animals to facilitate public viewing.

DISCUSSION: The Pryor Mountain Wild Horse Herd comprises a closed breeding system whereby additions to the population are primarily the result of an annual foal crop. Different social groups, within the population, can almost be predictably found in different areas of the range corresponding with home range preferences and seasonal activities. As a result, it is possible to concentrate culling activities on geographic subsets of the range corresponding to patterns of use by selected horses. This may permit successful removals of targeted horses without involving whole population gathers which have been the historical management technique. Subset gathers then, may involve: 1) bait- or water-trapping efforts (depending on the targeted section of range), 2) helicopter pressure into run-in traps located at various points throughout the range, and/or 3) temporary and reversible immunocontraception of targeted mares for foal crop reduction.

PLANNED ACTION: It is proposed, that with careful monitoring programs, culling efforts can be established which consider both the number of surviving foals from previous years and current conditions of range health. This effort is designed to encourage adaptability in management, generating long-term stability in available resources and range health. Re-evaluation of management techniques and results should take place at regular intervals.

BLM compiled data (Table 1) suggest an average annual foal crop of around 25-30 animals. Annual culling efforts should be maximized at this level. Once selective culling lists have been developed and approved, and information is available on migratory and use patterns of specific social groups, then gather activities on geographic subsets of the range can take place.

  1. Bait- or Water Trapping Efforts: Five bait and/or run-in traps currently exist on the Pryor range. These traps are currently in a state of disrepair and unusable. During the summer of 1996, BLM personnel with long-term expertise in trapping efforts are being brought in by the Billings Resource Area, to evaluate the design and functionality of these traps. Placement of these traps, with respect to designated wilderness areas, and accessibility for retrieval of captured horses will also be an important consideration. Upon evaluation, selected traps will be re-designed or re-vitalized to facilitate successful, non- intrusive, limited stress-inducing trapping. Subsequently (Sept/Oct 1996), contract professionals will be brought in, via standard BLM bid procedure, to provide construction efforts on the selected traps.

    The Dryhead area, within the Bighorn National Recreational Area, will be evaluated for water-trapping efforts, as well as helicopter run-in gathers. Permission will be needed from the National Park Service in order to construct possible temporary and/or permanent traps on this part of the range.

    Once the traps are ready for operation, a separate contract will be activated to employ qualified professionals to provide trapping services at designated traps and staggered time intervals. This timing must consider targeted animals and their migratory and seasonal use patterns of the range. Baiting may be in the form of hay, water or mineral salts. Once trapped, targeted animals will be transported to holding facilities at the Britton Springs Administration Site for preparation for adoption. Remaining animals will be released directly from the trap back onto the range. Initial trapping efforts may take place late fall 1996/early winter 1997 and resume summer 1997. Removal activities and trapping efforts will not take place during foaling season (April 1 through June 30 inclusive).

  2. Run-In Traps: The above bait traps will be evaluated and designed for a dual function and purpose. Some social groups of horses may never submit to bait trapping efforts and/or range resource availability may nullify trapping success. If bait/water trapping efforts are not successful, within an acceptable period of time, then it is important that these same traps be available as run-in traps involving helicopter efforts. The advantage to helicopter gathers is that the work can be accomplished within a much shorter period of time, reducing both management effort/costs and the potential risk of injury to horses due to confinement.

    Nationally-experienced, professional helicopter contractors for wild horses, exist, who recognize the enhanced risk of danger within the Pryor Mountain topography. It is possible to concentrate gathering by helicopter on subsets of the range, facilitating removal of targeted individuals, without subjecting the entire population to the stress of a gather. In this effort, positioning of the traps and timing of the effort would be such, that animals would not be pushed the entire length of the mountain. This is an important consideration for animal safety and well-being.

  3. Immunocontraceptive Efforts: Immunocontraception is currently not an approved management technique for the Pryor horses. However, research on other populations, demonstrates a possible one to three year contraceptive block as the result of injection with the appropriate vaccine. The vaccine itself, produces no apparent physiological side-effects or behavioral changes in the animals. Evidence, to date, indicates that targeted animals continue to cycle and are receptive to and bred by stallions. Targeted mares, captured in traps, can be vaccinated and released without additional transport or harassment. Once vaccinated the mares will develop levels of antigen surrounding eggs in their ovary, which serve as a chemical block to sperm penetration. After a few years, this process completely reverses itself, such that the mare may once again conceive and produce a foal.

    The advantages to this process are three-fold. Individual animals may stay on the range and live a natural lifestyle, without being subjected to gathers, removals and the stress of domestication. Secondly, targeted mares can again be reintroduced into the breeding cycle and contribute to the gene pool. This can be an extremely critical advantage when managing smaller, genetically restricted, breeding populations like the Pryor horses. If the horses were removed from the range, their future contribution to the gene pool would be lost forever. Finally, with a decreased size in annual foal crop, management typically becomes more cost-effective as intrusive removals are needed less frequently. Removals will still be needed, perhaps once every five years, with culled animals being available for adoption. Immunocontraception could be available for limited trials with selected Pryor mares as early as 1998. Public comment, consideration and approval will be needed before BLM adopts this method as a management strategy.


Activity within the Britton Springs Administrative Site will be limited primarily to PMWHR management. It is necessary to remove the existing corral facility, and construct a new. more simplified and efficient system to the northeast of the spring area. The current facility exists along the Britton Springs flow channel, and present surface run-off may, during times of heavy use, carry animal waste into the Crooked Creek water shed.

It is necessary to incorporate within the design, holding facilities which will allow gathered animals to be held for a maximum of four weeks prior to adoption. This is necessary in order to facilitate proper vaccination schedules for the horses. All restraining and preparation activities at this facility will be handled within a squeeze chute, except in rare situations where a given animal is dangerously resistant to restraint by this method.

DISCUSSION: Long-term (10-20 years) management projections indicate the decreasing need for whole population gathers (>100 horses), with instead, an emphasis on geographic subset gathers. The maximum required holding capacity of the corral system is estimated at about 100 horses, with an average PMWHR effort involving approximately 30 horses. A facility of this size will also facilitate the occasional BLM satellite preparation/adoption effort.

During times of confinement of Pryor Mountain horses, every effort will be made to insure sound equine management techniques are being followed. Particular attention will be given to animal health checks, consistent provision of appropriate hay and water, cleanliness of the facilities, appropriate use of veterinary services, and proper maintenance and supervision of the facilities to insure safety of the horses, BLM employees and the public.

PLANNED ACTION: Corral designs have been prepared, reviewed extensively by a variety of both BLM internal and external experts, and finalized (April 1996). These designs are on file and available to the public through the BLM-Billings Resource Area. The designs include separate holding pens for domestic horses used in PMWHR management efforts.

  1. Construction Efforts: The Navy SeaBees have volunteered to assist with construction efforts, targeting two weekends of effort - July 12/13/14 and August 2/3/4 1996. At the completion of these weekends, the new facility should be near-completed and the majority of the old structure should be demolished. Much of the materials comprising the old corrals will be recycled and used in the new facility. It is expected that the new facility will be fully operational within a 2-3 month period following these efforts. Reclamation of Britton Springs will be completed as soon as feasible following completion of the new facility.

  2. Maintenance Efforts: Prior to any scheduled gathers or adoption efforts, a site safety inspection will be held. This will permit facility repairs and improvements prior to housing any animals. During times of confinement of horses within the holding facility, consistent supervision will be provided by qualified BLM personnel and/or fully-trained and approved BLM volunteers. During all activities, detailed records will be kept, including but not limited to: 1) identification and health checks of each animal; 2) residency time of each animal within the facility; 3) timing of vaccinations and de-worming efforts; 4) need and use of professional veterinary services; 5) feeding, watering and corral cleaning schedules and checks; 6) physical facility maintenance and repairs; 7) adoption administrative activities.

    Following each gather and adoption effort, the BLM will undergo a self-evaluation process to help identify areas of management needing improvement and to solicit ideas for successful implementation. The BLM feels strongly that during the course of any culling or confinement activities, the health, well-being and safety of horses, employees and the public is equally paramount.


N/A indicates no available data
ALL data is approximate


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