Survival of desert mule deer fawns in central Arizona

Desert mule deer (Odocoileus hemionus eremicus) densities in central Arizona are below historic levels, likely due to neonatal mortality influencing desert mule deer population dynamics. However, no direct assessments have been made into causes and timing of neonatal mortalities in central Arizona. The objectives of our study were to determine the causes and timing of mortalities of desert mule deer fawns, estimate the annual survival rate of adult females and fawns, and quantify predator effects on fawn survival. In 2007 and 2008 we captured 52 adult female desert mule deer and equipped pregnant females with vaginal implant transmitters to aid in capturing fawns. We performed survival analyses using Program MARK and compared competing models with Akaike's information criterion. We captured 44 desert mule deer fawns; summer survival was 0.432 (95% CI = 0.292-0.584) and annual fawn survival was 0.071 (95% CI = 0.013-0.303). Predation accounted for 64% of fawn mortality. Probability of fawn survival was lowest in the first 2 weeks postparturition. Most (50 of 51) adult females of breeding age were pregnant and adult female survival was 0.858 (95% CI = 0.766-0.961). High predation rates and timing of predation on mule deer fawns were important factors influencing deer densities in central Arizona.