Our I.iviiii; Ri'soiini'.s — Ndii-nalive Species 



457 



Annual population growth in wild horse 

 herds varies from 5% to 259^. depending on 

 range and environmental conditions, with 15% 

 being a long-term average. At this rate of 

 increase, wild horse populations may double in 

 5 years. The annual growth in wild buno popu- 

 lations has not been determined, but their repro- 

 ductive capacity may be similar to that of wild 

 horse herds. 



The act specifies that wild horses and burros 

 may be managed only on lands where they 

 existed on December 15. 1971. the time of the 

 act's passage. The population of wild horses 

 and burros within those 1971 areas of use was 

 estimated at 17,000 animals; however, at that 

 time no formal inventory policies or procedures 

 existed to census populations. The BLM now 

 has 269 herd areas. 196 within which wild hors- 

 es and bunos are managed to some extent and 

 7.^ from which all wild horses and buiTos will 

 be removed. 



Wild horse and burro herd areas occupy 

 almost 43 million acres (17.4 million ha) of 

 public and prixate land in Arizona (about 4 mil- 

 lion acres or 1.6 million ha). California (6 mil- 

 lion+ acres or 2.4 million ha), Colorado 

 (800,000-F acres or 324.000 ha). Idaho 

 (450.000-1- acres or 182,250 ha), Montana 

 (55,000-1- acres or about 22,275 ha), Nevada 

 (nearly 19 million acres or nearly 8 million ha). 

 New Mexico (nearly 150.000 acres or 60,750 

 ha), Oregon (nearly 4 million acres or 1.6 mil- 

 lion ha). Utah (2.5 million acres or 1 million 

 ha), and Wyoming (nearly 6 million acres or 2.4 

 million ha)' (BLM 1993). 



Within most herd areas, wild horses and bur- 

 ros graze with domestic livestock and a variety 

 of indigenous wildlife species. Because they are 

 generalist species, wild horses and burros 

 inhabit a variety of habitats and vegetative com- 

 munities. 



The BLM's land-use planning process and 

 evaluation of cunent inventory and monitoring 

 data are used to detemiine a population level 

 that maintains a thriving natural ecological bal- 

 ance with other uses. The act directs BLM to 

 achieve appropriate population levels by 

 removals, humane destruction, or other options, 

 including antifertility methods. 



BLM no longer destroys healthy excess wild 

 horses and buiTos. Since 1973. when the first 

 removals occurred. BLM has removed 141,762 

 wild horses and burros from public land and 

 placed 122,627 animals into private care 

 through the Adopt-A-Horse program. 



Removing excess animals from populations 

 that exceed appropriate numbers is expensive, 

 has restricted BLM's attempts to pursue other 

 management alternatives, and therefore has 

 often allowed populations to increase dramati- 

 cally. When populations reached crisis propor- 



tions, funding was increased and large numbers 

 of excess animals were removed from the range 

 and placed with private citizens through the 

 adoption program. The number of animals 

 removed often was greater than the number that 

 could be adopted, resulting in high costs for 

 feeding and veterinary services while animals 

 were held pending adoption. 



In June 1992 the Director of BLM approved 

 the Strategic Plan for the Management of Wild 

 Horses and Bunos on Public Lands (BLM 

 1992). This plan represents BLM's first com- 

 prehensive policy for addressing wild horse and 

 buiTO management. To reduce the frequency of 

 removals, the plan recommends the use of 

 antifertility management to slow population 

 growth to a level where removals are only 

 required on a cycle of 5 or more years instead of 

 the current 3-year cycle. Pending the availabili- 

 ty of practical and cost-effective fertility-control 

 techniques, selective removal of animals based 

 on age or sex is being used to reduce the growth 

 rate in wild horse populations. The negative 

 aspects of selective removal include the diffi- 

 culty of predicting results through computer 

 modeling and the extensive monitoring needed 

 to ensure that age and sex ratios have not been 

 altered to a level that could threaten the herd. 

 Selective removals for controlling population 

 growth are considered a temporary management 

 option until research on immunocontraception 

 is completed and can be implemented. 



The BLM supports research on the use of 

 immunocontraception for controlling wild 

 horse population growth. Successful immuno- 

 contraceptive antigens have been developed; 

 researchers are now trying to develop a system 

 that would inhibit reproduction for 2 to 3 years 

 (J.F. Kirkpatrick. Deacones Medical Research 

 Institute. Billings, personal communication). 



Before the passage of the act, wild horses 

 and bunos were often captured and destroyed as 

 nuisances or were sold for profit, chiefly for use 

 in commercial products. The methods 

 employed in their capture and destruction were 

 often less than humane. As public awareness of 

 these animals grew, so too did support for fed- 

 eral legislation to protect them from inhumane 

 treatment. 



Public interest in the wild horse and burro 

 program continues to direct implementation of 

 the act. Since the act's passage in 1971, there 

 have been 44 district court suits and in excess of 

 200 appeals of BLM decisions to the Interior 

 Board of Land Appeals. 



References 



BLM. 1992. Strategic plan for the management of wild hors- 

 es and burros on public lands. Bureau of Land 

 Management. Washington. DC, 12 pp. 



74 76 78 80 82 



90 92 94 



Year 



Fig. 1. Wild horse and burro popu- 

 lation trends in BLM-administered 

 lands since passage of the Wild 

 Free-Roaming Horses and Burros 

 Act of 1971. 



Burros (7,500) 

 I Horses (39.000) 



25- 



20- 



15- 



i oL 



_ili«i— i_ 



^ 



AZ CA CO ID MT NV NM OR UT WY 

 State 



Fig. 2. Wild horses and burros in 

 199.1: population by state. 



