U.S. DEPARTMENT OF THE INTERIORBUREAU OF LAND MANAGEMENT
UNITED STATES DEPARTMENT OF THE INTERIOR
BUREAU OF LAND MANAGEMENT
WASHINGTON, D.C. 20240
January 15, 2009
In Reply Refer To:
4710 (260) P
EMS TRANSMISSION 01/15/2009
Instruction Memorandum No. 2009-062
To: All Field Officials (except Alaska)
From: Assistant Director, Renewable Resources and Planning
Subject: Wild Horse and Burro Genetic Baseline Sampling
Program Area: Wild Horse and Burro Program
Purpose: This Instruction Memorandum (IM) establishes program guidance and policy for the collection of genetic baseline information for wild horse and burro populations. This data will be beneficial to authorized officers and field specialists that are responsible for herd management decisions.
Policy/Action: The Wild Free-Roaming Horses and Burros Act requires that horses and burros on public lands be managed in a manner that achieves and maintains thriving ecological balance. Maintenance of such a balance frequently requires that wild horse populations be kept small. When population size is too small, it will inevitably lead to decreased genetic variation and possible inbreeding. However, it is possible to manage small populations in a manner that will minimize the loss of variation and inbreeding and if necessary, counteract the loss. The first step in this process is an assessment of the current genetic status of the population that will be followed by periodic monitoring assessments.
Genetic marker analysis can provide information about both the past and the future of a population. Because gene markers are passed from one generation to the next, they can tell us something about the ancestry of a population. Also, because demographics can affect the distribution of genetic markers within a population, these markers can often be used to interpret past populational characteristics. In the same way, current demographic conditions can be used to make predictions about the future level of variability of gene markers.
Prior to 2006, blood samples from wild horses and burros were collected during gather operations and analyzed by Dr. Gus Cothran (University of Kentucky) for establishing baseline genetic data. With Dr. Cothran’s move to Texas A&M University, this analysis is now being done using hair samples. A new baseline does not need to be established through hair analysis if blood analysis has already been completed. Unless there is a previously recognized concern regarding low genetic diversity in a particular herd, it is not necessary to collect genetic information at every gather. Typical herds should be sampled every ten to 15 years (two to three gather cycles). Following processing, a sample of DNA will be preserved (frozen) for each horse tested. A report on the analysis of the population will be provided by Dr. Cothran. Reports are to be kept on file at local Field Offices and also at the National Program Office. Attachment 1 contains the instructions for collecting, handling, and shipping of the hair samples.
While it is preferred to collect the hair samples from horses or burros that are released back to the herd management area (HMA), samples may also be collected from removed horses if necessary. In complexes or HMAs where separate breeding populations are thought to exist, each group of animals in a distinct population should be sampled separately. Do not mix samples from different horses or different breeding populations. Mixing samples from non-interbreeding herds can give misleading estimates of genetic variation. Minimum sample size is 25 animals or 25% of the post-gather population, not to exceed 100 animals per HMA or separate breeding population. Samples should be collected from males and females in the same approximate ratio as the population. Animals of any age class may be sampled. Burros should be sampled in the same manner as horses.
The data will be compared to similar data from both domestic and other wild horse/burro populations. The primary value of this initial data is a baseline against which future samples can be compared to identify genetic drift and any narrowing of diversity through inbreeding. In the short term, genetic diversity can be determined, rare alleles indentified and historic origins of and relationships among herds can be implied.
Timeframe: This IM is effective upon issuance.
Budget Impact: Costs associated with implementation of this IM will include the Bureau of Land Management (BLM) labor for collection of samples as well as sample processing and analysis at Texas A&M University. It is anticipated that costs for processing each sample will be $25-30 per sample while the analysis and reporting is estimated at $300 per report.
Background: The BLM has been collecting genetic health information about its wild horse and burro populations since the early 1990’s. To date, approximately 75% of the 199 HMAs that BLM administers have been tested and many have been retested. Based on this data, inbreeding is apparently rare in wild horse populations. Most wild horse herds that have been sampled exhibit moderate levels of genetic heterozygosity. Based on this analysis, approximately 12.5% of the herds tested have heterozygosity levels (observed heterozygosity (Ho)) below the assumed critical level of .310. These are herds that could begin to show inbreeding effects. Approximately 15% of the herds tested are within just 2% heterozygosity (.330) of the critical level. A population that is maintained at less than 100-120 adult animals may begin to lose variation fairly quickly. The herds that are just above the critical threshold level could drop very quickly. Only a very small number (approximately 5) of the 199 HMAs have exhibited characteristics possibly attributable to inbreeding, such as cataract blindness, dwarfism, parrot-mouth, or club-foot deformities. Thus, there does not appear to be any immediate cause for concern about inbreeding depression in wild horse herds.
Manual/Handbook Sections Affected: These monitoring requirements will be incorporated into 4710 handbook. This policy is consistent with the Strategic Research Plan – Wild Horse and Burro Management.
Coordination: The requirements outlined in this policy have been evaluated by the Wild Horse and Burro Research Advisory Team, reviewed by Field Specialists and coordinated with the National Wild Horse and Burro Advisory Board.
Contact: Questions concerning this policy should be directed to Alan Shepherd,
Wild Horse and Burro Research Coordinator, at the Wyoming State Office (307) 775-6097.
Signed by: Authenticated by:
Edwin L. Roberson Robert M. Williams
Assistant Director Division of IRM Governance,WO-560
Renewable Resources and Planning