Parts of the refuge are sometimes temporarily off-limits to visitors during training exercises on the adjacent Barry M. Goldwater Air Force Range, or because of law enforcement concerns with respect to illegal trafficking of people and drugs from Mexico. Additionally, parts of the refuge are temporarily off-limits to visitors between mid-March and mid-July, during the fawning season for the Sonoran pronghorn ("Antilocapra americana sonoriensis"), an endangered species endemic to the Sonoran Desert. The purpose of this closure is to minimize disturbance to herds containing fawns, which can result in the loss of fawns.