Study Finds Coyote Canyon Horses in Poor Condition

An ongoing study by the UC Davis Wildlife Health Center has found that most of the nearly three dozen feral horses living in Coyote Canyon are not healthy, center director Dr. Walter Boyce said today.

The Wildlife Health Center was asked last year by California State Parks to study the horses so that the parks department could better manage the natural resources of the canyon, which lies within Anza-Borrego Desert State Park. A small band of feral horses has been known to live in Coyote Canyon since the 1930s, when they escaped or were released from local ranches.

The Wildlife Health Center is a program of the UC Davis School of Veterinary Medicine. Walter Boyce is a veterinarian with a doctoral degree in parasitology and extensive experience studying the wildlife and ecosystems of Anza-Borrego Desert State Park and neighboring Cuyamaca Rancho State Park.

Under Boyce's direction, UC Davis doctoral student Stacey Ostermann and a team of assistants observed the population of 34 horses throughout the summer and into the fall. They found that many of the horses appeared to be in poor physical condition. Boyce then sought additional opinions from four equine experts.

On Feb. 6, Boyce, Ostermann, two equine veterinarians and two local horse experts inspected the canyon horses from helicopters and on foot. Twenty-nine of the 34 horses known to be in the canyon were seen at some point during the day.

Each of the four experts rated individual horses on a scale of 0 to 5. The ratings they gave ranged from 1 (poor) to 3 (good). No horse received any rating higher than 3, and there was general consensus that most of the 29 horses were in fair to poor condition.

The experts' written comments included:

  • Dr. Greg Ferraro, equine veterinarian and director of the Center for Equine Health at UC Davis: "In regard to the health status of these horses, it must be said they are walking a fine line between survival and extinction. These animals' grip on their existence is tenuous at best. Their physical condition indicates that they are only marginally nourished and their general appearance makes one suspect that they could be suffering from one of several different acquired or infectious diseases...The health status of these horses at the current time makes them extremely susceptible to any negative environmental factors... The introduction of the West Nile Virus this summer, an infectious disease that has been spreading rapidly over the U.S. the last three years and is expected in California this year, is an example of the type of event that could be devastating to these animals. In conclusion, it is my considered opinion that the health and welfare of the Coyote Canyon horses is unacceptable. To leave these horses to survive, as they currently exist, would be inhumane... The environmental conditions under which they exist are certainly not 'natural' for horses and not likely to provide for their long term survival."
  • Dr. Joe Cannon, equine veterinarian, San Luis Rey Equine Hospital: "Over a 7-hour period I was able to closely observe a number of horses and assess their health status. All of the horses were quite thin and some were in very poor flesh... Compared to photos of these horses taken in September 2002, the horses are presently in better condition. This is no doubt due to the feed available after some rainfall but they are far from acceptable condition... The similarity in color, markings and conformation indicate a very small gene pool of ranch type horses that have become feral... In summary, these horses are in poor condition and are struggling to survive in a harsh, unnatural environment. In their marginal, weakened state, a continuation of the present drought or the introduction of any added stresses would adversely affect their survival. In my opinion it is inhumane to allow these horses continued suffering in an environment that cannot adequately support them."
  • Joan Embery-Pillsbury, San Diego County resident: "Forage and water were sparse and it appeared that [the horses] remained in close proximity to the only available water and had overgrazed the immediate surrounding area. This over-utilization was evidenced by excessive trailing, high concentration of manure and limited forage... Their existence seemed marginal in relationship to the capacity of the environment to support them... it appears that these horses are struggling to survive in this harsh environment and with seasonal fluctuations in rainfall there may be times the environment cannot adequately support them..."
  • Gail Gregson, San Diego County resident: "My view would be best described as coming from a horse owner and breeder and as the public eye. I am also a resident of Borrego Springs, owning property since 1988... My first impression was, 'What on earth do they eat?'... There is some grass but it is very short and the land shows the effects of overgrazing... Their condition is minimal at best, and for the most part compromised. They are not really wild as some are quite approachable... With the little rain in the last few years, their survival looks precarious."

In conclusion, Walter Boyce said, "We are concerned about the health and welfare of these horses. With some rainfall and improved grazing since last summer, their condition has improved. But they are still not doing well, and West Nile Virus is likely to arrive in California this year.

"There is a vaccine to protect horses for West Nile, but it is not practical to administer the vaccine to free-ranging horses. The next step is to invite feral-horse experts from the federal Bureau of Land Management into the canyon to get their opinions and recommendations."

Two documents are available that provide more information (for copies, contact Sylvia Wright, below):

  • The expert evaluators' full reports are available in PDF format.
  • An August 2002 report of the anticipated effects of West Nile Virus on free-ranging horses in the western United States, prepared by the USDA Centers for Epidemiology and Animal Health, is available in Word format.

Media Resources

Kat Kerlin, Research news (emphasis on environmental sciences), 530-750-9195,

Walter Boyce, Wildlife Health Center, (530) 752-1401,

Mark Jorgensen, Anza-Borrego Desert State Park, (760) 767-4962,