Habitat use and survival of Sonoran pronghorn in years with above-average rainfall

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 (Parkinsoniaspp.)–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.