How the Pronghorn Came Back to Tejon
Photos and Story by California Naturalist and Conservancy Docent Chris Gardner
Pronghorn, Antilocapra americana, were once abundant in the grasslands and scrub-steppes of California. They evolved to outrun the American cheetah, an extinct predator, and are the fastest land mammal on the North American continent. Pronghorn can reach a top speed of nearly 60 mph. Their speed, combined with their extremely sharp eye sight, allow them to detect and outrun most modern predators.
The arrival of settlers in the Antelope Valley in the late 1800’s to early 1900’s resulted in the fencing of the pronghorn’s historical open ranges. Pronghorn, unlike deer, are incapable of jumping fences, which severely limits their speed advantage needed for escaping predators. The combination of the conversion of their native grasslands to cultivated crops and overhunting resulted in the disappearance of the pronghorn in the Antelope Valley in the early 1900’s.
In 1985, the California Department of Fish and Game, as it was then known, translocated 17 males and 37 females from Modoc County to the Tejon Ranch. In 1987, an additional 3 males and 37 females were translocated. At the present time, the herd on the Ranch consists of 27 to 28 individuals.
During the years 1987, 1988 and 1990, Fish and Game also translocated just over 200 Pronghorn to the Carrizo Plain. The Carrizo Plain population first increased, began to fluctuate, and then declined. By 2012, the Carrizo Plain population was estimated to be fewer than 30 individuals.
Four primary factors have been found to contribute to the decreasing population of pronghorn in general: predation, starvation, exposure, and disease. For the pronghorn on the Ranch and the Carrizo Plain, only predation has been found to be significant. Predators include coyotes and golden eagles. Studies show that survival rates of juveniles is far lower than survival rates of adults.
It has been noted that on the Ranch, cattle grazing may reduce fawning cover, which is necessary to hide the fawns. However, grazing may be of benefit in that it can result in increased amounts of forbes and shrubs that are preferred by pronghorn. Further, cattle grazing may reduce vegetative cover, resulting in better long-range sighting and avoidance of predators.
The survivability of fawns appears to be critical in the long-term success of the herd. Studies on the Carrizo Plain have found that more fawns are born each year than on the Ranch. However, the survivability of the fawns is much poorer on the Carrizo Plain than on the Ranch. As such, it appears to this observer that the pronghorn on the Ranch receive a direct benefit from the ranching activities.
A special thank you to the Citizen Science Pronghorn Team for their continuous monitoring efforts. If you’d like to become a Tejon Ranch Conservancy volunteer please contact Chris Fabbro at (661) 699-2085 or by email at email@example.com.