California condors (Gymnogyps californianus) released into the wild in Arizona ranged widely in Arizona and Utah. Previous studies have shown that the blood lead concentrations of many of the birds rise because of ingestion of spent lead ammunition. Condors were routinely recaptured and treated to reduce their lead levels as necessary but, even so, several died from lead poisoning. We used tracking data from VHF and satellite tags, together with the results of routine testing of blood lead concentrations, to estimate daily changes in blood lead level in relation to the location of each bird. The mean daily increment in blood lead concentration depended upon both the location of the bird and the time of year. Birds that spent time during the deer hunting season in two areas in which deer were shot with lead ammunition (Kaibab Plateau (Arizona) and Zion (Utah)) were especially likely to have high blood lead levels. The influence upon blood lead level of presence in a particular area declined with time elapsed since the bird was last there. We estimated the daily blood lead level for each bird and its influence upon daily mortality rate from lead poisoning. Condors with high blood lead over a protracted period were much more likely to die than birds with low blood lead or short-term elevation. We simulated the effect of ending the existing lead exposure reduction measures at Kaibab Plateau, which encourage the voluntary use of non-lead ammunition and removal of gut piles of deer and elk killed using lead ammunition. The estimated mortality rate due to lead in the absence of this program was sufficiently high that the condor population would be expected to decline rapidly. The extension of the existing lead reduction program to cover Zion (Utah), as well as the Kaibab plateau, would be expected to reduce mortality caused by lead substantially and allow the condor population to increase.

Since 1996, The Peregrine Fund has released California condors (Gymnogyps californianus) in the Grand Canyon region of northern Arizona with the goal of establishing a self-sustaining population, disjunct from other released populations in California and Baja California. A free-ranging population of more than 60 individuals now ranges within northern Arizona and southern Utah and has produced 9 wild young. The most frequent cause of death is lead poisoning from the ingestion of lead bullet fragments and shotgun pellets in the remains of gun-killed animals. In response, the Arizona Game and Fish Department has effectively reduced lead occurrence within the foraging range of the condors through hunter education and the promotion of nonlead ammunition. Most hunters have participated in the program. Throughout the course of the reintroduction effort, veterinary science and application have played essential roles in diagnosing fatalities and treating lead-exposed condors, a species with such a low natural reproductive rate that every adult is significant to the population.

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