THE endangered California condor faces an "epidemic" of lead poisoning from scavenging carcasses contaminated by lead bullets despite years of costly conservation efforts.
The rare birds were reduced to a population of just 22 in 1982, and have since recovered to number about 400, with half of those still in captivity, said the study in the Proceedings of the National Academy of Sciences.
About five million dollars are spent per year on programs to boost the birds' population through captive breeding and release programs. But if those efforts were to cease, the birds would likely die off again, said the study.
Lead poisoning remains a critical danger, and efforts to limit the use of lead bullets by hunters in California in the past few years have not cut down on the number of chronic poisoning cases, researchers said.
"We will never have a self-sustaining wild condor population if we don't solve this problem," said first author Myra Finkelstein, a research toxicologist at the University of California Santa Cruz.
"Currently, California condors are tagged and monitored, trapped twice a year for blood tests, and when necessary treated for lead poisoning in veterinary hospitals, and they still die from lead poisoning on a regular basis."
Each year, nearly a third of condor blood samples showed serious lead exposure and 20 percent of free-flying condors in California are found to have blood lead levels that require treatment, according to the researchers.
Without chelation therapy to remove lead from the blood, birds can suffer paralysis, stiff joints and lose their ability to fly. At high levels, lead poisoning can kill.
The effects of chronic sublethal lead poisoning on the central nervous system are unknown and deserve further study, the authors said.
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