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An adult prognhorn antelope --Photographer: USFWS
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Tracking Pronghorn Antelope in California’s Central Valley

When we hear that verse from “Home on the Range” about where the antelope play, most people aren’t thinking of Bakersfield -- or San Luis Obispo for that matter.

Yet halfway between these California cities is the Carrizo Plain National Monument, some 200,000 acres home to the largest remaining remnant of the original San Joaquin Valley habitat. It is one of America’s newest national monuments, and it’s a landscape that offers a glimpse of what California looked like in millennia past.

A California that still had herds of pronghorn antelope (Antilocapra americana).

Historically, pronghorn were found on the Carrizo Plain, as well as other areas in southern California. However, due to extensive habitat fragmentation through conversion of native grasslands into agricultural areas, the species was locally extinct throughout the region by the 1940’s. Pronghorn were reintroduced to Carrizo Plain in the 1990’s in part to reestablish a historic population, but more broadly, to help restore a native ecosystem. As large herbivores, pronghorn play an important role as grazers, seed dispersers, and even prey items in natural communities.

This gives Carrizo Plain officials a special challenge in balancing its responsibilities of managing both the survival of the new pronghorn population and the existing permitted livestock grazing.

To help collect data on the life history of Carrizo Plain pronghorns, USGS Western Ecological Research Center scientists Kathy Longshore and Diego Johnson have been tracking pronghorn fawns with GPS transmitter collars to study their survival and mortality.

Diego Johnson preparing to examine a pronghorn fawn at Carrizo Plain National Monument. --Photographer: Sara A. Schuster/USGS
Diego Johnson approaches a pronghorn fawn. Image credit: Sara A. Schuster/USGS.

Johnson, who is also a graduate student at University of Nevada, Las Vegas tells us more about his research here:

Q: Most people don’t equate pronghorn with California. What was their range in this state during prehistory?
  Actually, California’s once extensive native grasslands and mild climate would have been exceptional pronghorn habitat.  In fact, pronghorn were considered common in southern, central and northern California and were found on both sides of the coastal range, from Monterey well into Baja California.

Q: What kind of management questions will your studies help answer for the Bureau of Land Management?
Understanding the biotic and abiotic factors which influence survival is essential to effectively manage any wildlife population. One important component of our research focuses on fawn survival. We are interested in how factors such as birth synchrony, habitat use, and predation can act together to influence fawn survival and overall population dynamics. What type of vegetation structure is important for a hiding fawn or a foraging mother? How is predation influenced by fawn habitat selection and spatial movement? How does the density of a population affect survival? These are just a few of the questions that can be addressed by land managers using information from our research.

Q: What are some factors affecting fawn survival in the Carrizo pronghorn?
The most significant natural factor affecting pronghorn population dynamics is fawn mortality due to predation. Fawn predation is naturally high in most pronghorn populations (40-80%) and in fact, fawns provide an important, natural food source for predators during the early spring of each year.  However, in habitat with poor vegetative cover for hiding or in low density populations, such as that found in the Carrizo, the effects of predation can increase. In the Carrizo, the top predators of fawns include coyotes, golden eagles, and bobcats, and we want to figure out how land managers can encourage fawn survival while allowing natural predator-prey interactions.

Q: What’s it like holding a live pronghorn fawn in your arms?
  The fawns that we handle are typically between 2-5 days old. Their hiding instinct is incredibly strong during this period so they often remain motionless while we process and collar them.  They have enormous dark eyes and comically long limbs -- you image that they have the tools to one day see far and run fast on a flat open Carrizo grassland.

-- Ben Young Landis

Top photo of adult pronghorn courtesy of U.S. Fish and Wildlife Service.

Sara A. Schuster approaches a pronghorn fawn in Carrizo Plain National Monument. --Photographer: Diego Johnson/USGS
This pronghorn fawn is freezing in motion to hide from biologist Sara Schuster. Image credit: Diego Johnson/USGS.

A pronghorn fawn at Carrizo Plain National Monument --Photographer: Diego Johnson/USGS
A fawn fitted with a GPS transmitter collar. Image credit: Diego Johnson/USGS.

Pronghorn fawns after tracking collar installation at Carrizo Plain National Monument. --Photographer: Diego Johnson/USGS
The big doey eyes of pronghorn fawn. Image credit: Diego Johnson/USGS.

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