The Bureau of Land Management (BLM) has managed the once healthy and thriving burro population in the western United States into to a crisis situation. According to the BLM’s most recent (2014) population estimate, there are only 8,394 burros remaining in the entire West!
The BLM’s lead equine geneticist, Dr. Gus Cothran, a clinical professor of Veterinary Medicine and Biomedical Sciences at Texas A&M University, has stated that the U.S. burro population is at a genetic breaking point thanks to the many BLM roundups (euphemistically referred to as “population contractions”) that have reduced the population to tiny, fragmented herds, resulting in a situation that has caused a dangerous increase in inbreeding. In fact, many burro populations have only a 20 percent (20%) genetic variability factor compared to a healthy genetic variability of 70%.
At 50% variability, a population is considered “challenged." These facts led the National Academy of Sciences (NAS) to warn in its 2013 report that "removing burros permanently from the range could jeopardize the genetic health of the total population." The NAS investigation also concluded that the BLM "may need to assess whether the AMLs [Allowable Management Levels] set for burros can sustain a genetically healthy total population."
When the statistics for wild burro herds are isolated from wild horse numbers the picture is even more dismal for burros. Of the 56 Herd Management Areas (HMAs) containing wild burros, only 14 still maintain borderline genetically viable populations. Under BLM management plans, only five of these HMAs (only 9% of them) allow for a truly genetically viable population of 150 animals or more! Even the Marietta Wild Burro Range of west central Nevada, the only Congressionally designated wild burro range in the country, has nowhere near the number of burros required to maintain a genetically viable population. Just 85 burros are allowed under the current BLM management plan for this remote area that extends over 66,500 acres.
In similar cases with a few wild horse herds, the BLM has introduced horses from other herd areas to try to offset extremely low AML's (i.e., Bordo Altravesado—AML=50, Little Book Cliffs—AML=80), ignoring and undermining the unique characteristics that each herd originally exhibited or has developed over years, if not centuries, of natural selection—i.e., the Spanish genetics of the Pryor and Cerbat herds, the unusual color genetics in some herd areas, the survival adaptations of most individual herds, etc.
e the genetics with outside introductions, we believe it is more prudent, scientifically sound, and less expensive to simply allow existing populations to increase to genetically viable levels. This may require re-writing management plans, decreasing the available AUM's for livestock grazing in the herd areas, expanding herd area boundaries, or simply allowing levels to rise naturally over time within each area in jeopardy. A leader in the field of equine population genetics, Dr. Cothran has collected blood and hair samples from equines around the world, and also analyzes blood samples from U.S. wild horses and burros for the BLM. Dr. Cothran suggests that managing wild horses at low population levels makes them vulnerable to long-range loss of genetic diversity. This is the same problem that plagues many endangered species around the world. But, just how small is too small? At what point do wild horse and burro populations suffer the risk of irreparable genetic damage?
Based on his DNA analysis, Dr. Cothran believes that the minimum size for both wild horse and burro herds is between 150-200 animals. Within a herd this size, about 100 animals will be of breeding age. Of those 100, approximately 50 animals would comprise the genetic effective population size. That is, these 50 animals are those that are actually contributing their genes to the next generation. Dr. Cothran has stated that 50 is the absolute minimum number. A higher number would decrease the chances for inbreeding; the higher the number, the lower the occurrence of inbreeding.
Watch Dr. Cothran's presentation to the NAS Panel on the BLM Wild Horse and Burro Program below!
Addressing the Problem
In order to uphold the letter and the spirit of the Wild Free Roaming Burros Act of 1971 and protect wild burros (and horses) as "natural components" of the lands on which they are found, the BLM must increase Allowable Management Levels (AMLs) for wild burro populations. One place to start is by designating the Black Mountain Herd Mountain Area in Arizona -- home to the nation's largest, most genetically healthy and robust wild burro population -- as a National Wild Burro Range, designated principally for use by wild burros as a sanctuary for these historic and publicly cherished animals. You can help make this goal a reality by signing the petition below.