By: Karen Schutte | August 26, 2026
The Arizona Board of Regents is scheduled to consider a $325,000, two-year Regents’ Research Grant for genetic testing of the Salt River Horse Herd sometime between 2:15-2:30 at its August 27 meeting. The project brings together researchers from Northern Arizona University and the University of Arizona, with participation from the U.S. Geological Survey, the Southern Arizona Experiment Station and the Salt River Wild Horse Management Group.
What AZDA Asked the Researchers to Determine
The Arizona Department of Agriculture requested the study to help answer a question that has never been scientifically resolved for the Salt River herd: What population size and herd composition are necessary to maintain long term genetic sustainability?
In its request, AZDA said it wanted a comprehensive evaluation of the herd’s current genetic diversity, along with options for the “minimum size and characteristics of a genetically sustainable herd” within the Salt River Horse Herd management area.
AZDA specifically asked the research team to provide science-based information on:
- The current genetic makeup and diversity of the Salt River herd.
- The herd’s current gender diversity.
- Options for maintaining genetic diversity while determining a minimum population capable of long-term sustainability.
- The balance of males and females needed to support the herd’s long-term sustainability.
- Options for humane removals, if needed, that would protect the herd’s genetic diversity and maintain a healthy balance of males and females.
- A method for identifying individual horses most important to the long-term health and welfare of a genetically sustainable herd.
There is one aspect of AZDA’s request that deserves close attention. Its language includes maintaining genetic diversity while “minimizing” the Salt River horse population. That indicates AZDA is approaching the study in part from a population reduction standpoint. However, AZDA also explicitly asked researchers to determine the minimum size of a genetically sustainable herd rather than supplying that number in advance.
That distinction will be important as the study moves forward. The science should be allowed to determine the sustainable population rather than being used to justify a predetermined target.
What the Research Team Proposes to Do
The proposal goes considerably beyond basic genetic testing.
The researchers describe their overall goal as evaluating the herd’s genetic health, diversity, relatedness and long-term viability using modern genomic tools in order to inform science-based management and conservation decisions.
The study has three major objectives.
Objective 1: Characterize the current genomic health and demographic structure of the herd.
Researchers will quantify genomic diversity and population structure, estimate the herd’s effective population size, calculate inbreeding and relatedness, and examine the genetic relationships among individual horses.
Objective 2: Determine the minimum genetically sustainable herd size and composition.
Using data gathered under objective 1, researchers will run forward time genetic simulations incorporating genomic information as well as demographic factors including birth and mortality rates, sex ratio and age composition. These simulations are intended to project the genetic consequences of alternative management strategies over time.
Objective 3: Translate the genomic findings into management guidance.
The researchers intend to combine genomic and demographic modeling into science-based recommendations that can be used by AZDA and other stakeholders in future herd management decisions.
The proposal also examines different hypothetical removal strategies, including random removal, demographic removal, low diversity removal, kinship aware removal, family unit removal and genomic optimization. The purpose is to determine how different management approaches could affect genetic diversity over time.
A diagram in the proposal shows modeled herd sizes of 250, 225 and 200 animals. Those figures appear to be example management scenarios rather than a stated final population target, but this is an area worth clarifying during the Regents’ discussion. The key scientific question should remain open: If the data indicates that a sustainable population needs to be greater than 200, the research design should allow that result.
The Research Team
The project combines expertise in genomics, wildlife biology, conservation genetics, population modeling and direct knowledge of the Salt River herd.
Dr. Jeffrey Foster, Northern Arizona University
Foster is a professor and wildlife biologist at NAU with expertise in wildlife genomics and infectious diseases. His work includes population and comparative genomics and the application of genomic tools to wildlife conservation questions.
Dr. E. Anne Chambers, Northern Arizona University
Chambers is an assistant professor and wildlife biologist whose research includes large scale whole genome sequencing projects and genomic analyses of wildlife populations. Her work includes evaluating genetic diversity and population structure using modern genomic tools.
Dr. Faith Walker, Northern Arizona University
Walker is an associate research professor and molecular ecologist with more than 25 years of experience using genetic tools for wildlife conservation and management. Her research includes noninvasive DNA sampling and methods for extracting genetic information from wildlife fecal samples.
Dr. Jessica Rick, University of Arizona
Rick is an assistant professor and wildlife biologist specializing in population and conservation genetics of wildlife. Her research includes population genomics and phylogenomics, as well as the use of genomic sequencing to answer conservation and management questions.
Dr. Leigh Combrink, University of Arizona
Combrink is an assistant professor and wildlife biologist with experience in wildlife disease and conservation. Her work includes noninvasive sampling and genetic methods used in wildlife population research and conservation.
Dr. Jacob Hennig, University of Arizona
Hennig is an assistant professor and Cooperative Extension specialist in Public Lands Grazing at the University of Arizona. His work includes population size estimation, wildlife ecology and management issues involving wild equids.
Dr. Kate Schoenecker, U.S. Geological Survey Fort Collins Science Center
Schoenecker is a supervisory research wildlife biologist and branch chief with USGS Fort Collins. She is a nationally recognized wild horse researcher whose work has focused on population ecology, management and conservation of free roaming horses and burros.
Dr. Sara Oyler McCance, U.S. Geological Survey Fort Collins Science Center
Oyler McCance is a supervisory research geneticist and internationally recognized conservation geneticist. Her work on wild horses has included population size, genetic diversity, population structure and long-term herd viability.
Brett Blum, Southern Arizona Experiment Station
Blum is Interim Director of the Arizona Experiment Station and Director of the Southern Arizona Experiment Station. In this project, he is expected to advise the research team on project deliverables, stakeholder communication and wild horse biology, including knowledge gained through prior work involving the Salt River herd.
Simone Netherlands, Salt River Wild Horse Management Group
Netherlands is the director of the Salt River Wild Horse Management Group. SRWHMG volunteers will assist with fecal sample collection and individual horse identification. The proposal specifically states that SRWHMG’s detailed knowledge of the herd and its ability to identify individual horses is crucial to the project.
What to Listen for During the Regents Meeting
The central issue is whether the project will truly allow genetics and demographic modeling to determine the herd’s sustainable population.
The key questions to listen for are:
- Is 200 merely one modeling scenario, or is it being treated as an upper boundary?
- Will the researchers be free to conclude that the minimum genetically sustainable population is greater than 200 if the data supports that result?
- Will previous genetic samples or historical genetic information from the herd be incorporated where scientifically appropriate?
- How will genetic sustainability be balanced against other management considerations once the study is complete?
- And most importantly, will future population decisions be based on the findings of this study rather than on population targets established before the study is finished?
The significance of this grant is that it moves the Salt River horse debate toward the question advocates have repeatedly asked: What does the science show is necessary to keep this herd genetically healthy and sustainable for generations to come?
Read the full scope of the research study here.