According to a newly published report from the University of California, Santa Cruz, condor populations in that state are being affected by lead in ammunition. Study author Myra Finkelstein notes that, “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.”
Lead poisoning in the condors is now “of epidemic proportions,” said Ms. Finkelstein, a research toxicologist at UC Santa Cruz and the principal author of a report on the condor problem in this week’s issue of the Proceedings of the National Academy of Sciences.
In a study led by Finklestein’s team at UC Santa Cruz, the source of the lead poisoning was traced back to ammunition via isotope testing. Whereas captive condors have lead isotope “fingerprints” which match that of background environmental lead in California, the wild condors have been found to have an isotope fingerprint which matches that of lead ammunition. The researchers worry that deaths from lead poisoning are hampering recovery of the condor population. Finkelstein says, “We will never have a self-sustaining wild condor population if we don’t solve this problem.”
The California birds are an iconic endangered species, and are very sensitive to changes in their environment. The condor population dropped to a low of only 22 individuals in 1982, and has only slowly recovered, thanks to concerted efforts on the part of scientists and conservationists. The total condor population today is about 400 birds.
“We will never have a self-sustaining wild condor population if we don’t solve this problem,” said Ms. Finkelstein.
The researchers note that wild populations, though increasing, are still unsustainable without intensive human management and the regular introduction of captive-raised condors. When wild condors are found with significant lead poisoning, researchers treat them in zoos until they are healthy enough to be returned to the wild. Solving the problem of lead poisoning is a key component in helping the wild populations establish a stably reproducing population.
As of May 31, the condor population stood at 416, with 236 flying free in California, Arizona and northern Mexico, and 180 living in a handful of breeding operations, such as Oregon’s. Since 1997, about half of all the free-flying birds in California have required chelation therapy to remove lead from their blood, say scientists.
Condors are scavengers, and consume lead when they feed on carcasses which contain the ammunition. Finkelstein notes that even small amounts of exposure appear to be enough to cause problems for the condors. “We found that over the course of 10 years, if just one half of one percent of carcasses have lead in them, the probability that each free-flying condor will be exposed is 85 to 98 percent, and one exposure event could kill a condor.” Lead based ammunition is already banned in condor-populated areas, but the researchers advocate for greater regulation of lead-based ammunition in California.
The results of the study are published in the Proceedings of the National Academy of Sciences, and the study was supported by the National Park Service, the Western National Park Association, and the U. S. Fish and Wildlife Service.