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Abstract
Sonoran pronghorn (Antilocapra americana sonoriensis) occur in an arid desert in northwestern Sonora, Mexico and southwestern Arizona; their numbers have declined since 1920. Causes of the decline are largely speculative but include habitat alteration by humans, excessive herbivory by domestic livestock, illegal harvest, and exposure to domestic livestock diseases. We initiated this study to develop information on habitat use and survival to aid in developing recovery strategies for Sonoran pronghorn. We captured 19 Sonoran pronghorn and monitored their movements and habitat use patterns from 1983 through 1991 and compared these locations to random locations to assess habitat use. We also calculated survival. Sonoran pronghorn used the creosote bush (Larrea tridentata)-white bursage (Ambrosia dumosa)-paloverde (Parkinsonia spp.)-mixed cacti association greater than expected. Locations of Sonoran pronghorn close to water occurred more frequently than random locations, and areas farthest from waters were used less than expected. Sonoran pronghorn used areas within 1 km of roads less than random locations and used locations >1 km from roads as expected or greater than expected as distance from roads increased. Mean annual estimated survival for females and males was 0.96±0.04 and 0.92±0.04, respectively. Sonoran pronghorn had very low mortality rates and the population expanded to levels that likely have not occurred since the 1920s.
Key Words
Antilocapra americana sonoriensis, Arizona, habitat use, mortality, Sonoran pronghorn
The Sonoran pronghorn (Antilocapra americana sonoriensis) is 1 of 5 pronghorn subspecies recognized from North America. This subspecies occurs in the Sonoran Desert of northwestern Sonora, Mexico and southwestern Arizona. Historically, Sonoran pronghorn distribution was more widespread than today, once ranging as far south as Bahia Kino and Hermosillo, Sonora, north to Gila Bend and the Palomas Plains in Arizona, and into southeastern California. Currently, distribution is restricted to a small area of its former range in Arizona and Sonora (Carr 1971, Arizona Game and Fish Department [AGFD] 1981, Hoffmeister 1986, Wright and de Vos 1986).
Sonoran pronghorn is a desert-adapted subspecies, occurring in a range with environmental extremes including summer temperatures that regularly exceed 45°C with sparse rainfall (Turner et al. 2003). Areas occupied by Sonoran pronghorn have low plant density, and dominant shrub species offer little forage value (Wright and de Vos 1986). These environmental and habitat extremes continue to place...