Conservation

Photo courtesy Ron Niebrugge www.wildnatureimages.com

Pronghorn can be susceptible to human interference. Historical population estimates are as high as 60,000,000. In 2000, however, the population of pronghorn in North America was estimated at only 799,200 (Krausman et al., 2005). European settlement in the west had devastating effects on pronghorn populations, and they were reduced to less than 1% of their numbers by the end of the 19 th century (Yoakum and O'Gara, 2000).

Over-hunting was one of the primary reasons for the initial decline, but there is evidence that even recreational use of pronghorn habitat can have potential negative effects. Pronghorn were reintroduced on Antelope Island in the Great Salt Lake in 1993. the population was monitored for four years, during which time the park was opened for hiking, mountain biking, and horseback riding. After the trails were opened, pronghorn distributions shifted away from the trails. In 1998, the construction of a paved road in an important fawning area forced females to move their birthing areas to higher elevations. This event coincided with the highest fawn mortality rates seen since 1990 (Fairbanks and Tullous, 2002).

Pronghorn are known to migrate up to 550 km in a year, from the Upper Green River Basin to Grand Teton National Park. This extreme long distance migration is adjacent to the Greater Yellowstone region, where almost 75% of migration routes have been lost because of habitat disturbance such as fences, highways, and subdivisions. It is important to conserve these regions, because these animals follow distinct paths that wind through very narrow corridors (Berger, 2003).

Of particular conservation importance is a subspecies of the American Pronghorn, the Sonoran Pronghorn. It was listed as an endangered species in 1967, and is currently restricted to less than 25% of its historical habitat in Arizona and Mexico. In December 2004, the U.S. population was estimated at only about 50 animals (Krausman et al., 2005). Populations in Arizona and Mexico are not able to exchange migrants because of the fencing on the U.S.-Mexico border. Bottleneck effects and drift have been severe in both populations, and with such low genetic diversity this subspecies may be doomed to extinction unless serious conservation efforts are implemented (Stephen et al., 2005).