The Sonoran pronghorn (Antilocapra americana sonoriensis) has been listed as endangered since 1967, yet little is known about its behavior due to difficulties observing them in the wild. During a study of Sonoran pronghorn in a semi-captive breeding facility in southern Arizona, we observed behaviors and timing of life-history events that have not been documented in peer-reviewed literature, including birth dates of fawns, pre-parturient and post-parturient behavior, timing of breeding season, behavior during the breeding season, date of horn casting by males, and response to predators. Behavior of the Sonoran pronghorn before and after parturition, during breeding, and toward predators was consistent with that reported for other subspecies. Timing of breeding, parturition, and horn casting all occurred earlier than reported for more northerly populations. Variation in timing of life-history activities was the main difference between the Sonoran pronghorn and other subspecies and would be expected due to the correspondence between seasonal rainfall and forage conditions in the Sonoran Desert and timing of parturition.