Earth Notes: Surveying Arizona's Pronghorn Populations

Jul 8, 2020

It can be a thrilling sight to see a herd of pronghorn running across wide open space. This swift, Indigenous North American animal, is colloquially known as an “antelope,” but in fact, it isn’t related to Old World antelope at all.

Credit Michael Collier

Arizona’s pronghorn population is estimated at 9,000 to 10,000 animals--mostly the subspecies American pronghorn. But those numbers can fluctuate widely from year to year.

Aerial surveys are one tool for getting at these estimates. Arizona Game and Fish conducts flights usually every other year in August and September. A fixed-wing airplane flies transects, with two observers on the same side of the plane to provide independent observations. Besides getting good numbers, they can tell adults and juveniles, along with the ratio of bucks to does, and does to fawns. Survey and hunter information are fed into computer models, guiding recommendations for hunting and other management actions.  

Pronghorn on Anderson Mesa and surrounding lowlands southeast of Flagstaff have been watched for decades. As with all pronghorn, survival of fawns—the future of the herd--is of special concern. In some years, surveys have found no fawns; in other years, their numbers can increase dramatically.

A combination of factors can affect both fawns and adult pronghorn--drought and heavy snows; elk and livestock presence; water sources; predation; and fencing, houses, and highways that block movements—making it even more important to accurately count them, and learn how the herds and their habitat are faring.