Lead Poisoning

Posted at 11:50 pm February 6, 2008 by Bill Toone

This is the most crucial roadblock to the recovery of the California condor. Exposure to lead is a well-recognized danger to humans, mammals, and birds. After a 20-year effort to bring the California condor back from the brink of extinction, lead poisoning continues to be a threat to the recovery of the species.

Lead poisoning is not a new issue. For more than 2,000 years people have known that lead is toxic. Where there are direct threats to human health, the issue has been reasonably well addressed. Lead has been removed from paint, our gasoline and numerous other products.

Lead works by attacking the nervous system therefore neurological problems of enormous variety can occur. In humans these may include reduced cognitive abilities, lethargy, seizures and even comas.

In condors we generally see early effects of lead poisoning in the form ataxia (loss of balance and inability to fly). Later effects are generally a result of damage to nerves that control the digestive system. Loss of appetite and associated weight loss can occur rapidly. If not treated quickly, the damage to the nervous system is irreversible and leads to a slow and agonizing death.

Studies have shown that lead bullets defragment while passing through an animal. Consequently, animals eating this meat will unknowingly ingest bits of lead. This includes scavengers like bald eagles, bears, coyotes and wolves. In addition, humans eating the meat may also ingest lead fragments and potentially be exposed to many of the same problems as we see in birds.

Caught early, before damage to the nervous system, lead poisoning can be effectively treated with a chelating agent such as DMSA or EDTA. Sadly it is often not detected before it is too late in wild birds. The best solution is to be sure that birds, other wildlife and people are not exposed to lead in the environment at all.

Effects on Birds in California
Elevated levels of lead have been found in 44 percent of the condors released in Southern California and 21 percent of those released in Big Sur. A total of 94 free-flying condors disappeared or died between 1992 and August 2006. Of these, the cause of death has been determined for 61 condors, and 25 percent of these died of lead poisoning.

Effects of Birds in Arizona
Indications of lead exposure prior to the fall deer-hunting season were unremarkable, but after hunting began in late October, some 95 percent of the population showed evidence of exposure, 70 percent required treatment, and four birds died of lead poisoning. Four showed metal fragments in x-rays of their digestive systems.

What’s being done?
California Condor Recovery Team members closely monitor free-flying condors and conduct annual health examinations. If a condor is found to have high levels of lead in its blood, it is treated at a zoo veterinary medical center and released in its home territory.

Hunters are ensuring they properly dispose of “gut piles” (the intestines and vital organs they don’t want). This is where the majority of the lead fragments are found by birds.

Where can I get more information?
o Exposure of California Condors to lead from Spent Ammunition – Cade, TJ, 2007 - Journal of Wildlife Management http://www.peregrinefund.org/pdfs/ResearchLibrary/Cade%202007.pdf
o Lead Ammunition: Implications for Wildlife and Humans – Conference convened by The Peregrine Fund 12 – 15 May 2008
o UC Santa Cruz study http://www.cbse.ucsc.edu/news/2006/08/31/condor/index.shtml
o California Department of Fish and Game http://www.dfg.ca.gov/wildlife/hunting/condor/
o UC Davis Wildlife Health Center Report on lead toxicity in Condors prepared for the California Fish and Game Commission Wildlife Branch http://www.vetmed.ucdavis.edu/whc/condors.cfm
o http://en.wikipedia.org/wiki/Lead_poisoning

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