SACRAMENTO, Calif. -- Lead poisoning is killing California's endangered condors, two new studies say, prompting new guidelines for hunters who leave more than 30,000 lead-laced carcasses for the carrion scavengers each year.
The latest condor to die was shot by a hunter in February, less than two months after spending six weeks in a zoo hospital being force-fed food and medicine to counteract lead poisoning likely contracted from eating ammunition fragments.
Adult condors not only consume the lead from carcasses, but pass on the lead poisoning to their offspring, scientists said.
The problem is endangering efforts to rescue the giant birds from near extinction. The wild population dropped to just 15 in 1984, before a captive-breeding program brought the world's population back to 221.
Eighty-two condors now inhabit the California mountains bordering the San Joaquin Valley; northern Arizona and southern Utah; and northern Baja California. Adult condors may travel up to 150 miles in a day to forage for food.
The condors apparently consume lead frequently as they feed on hunter-killed wildlife, according to a study for the California Department of Fish and Game by D. Michael Fry of the Department of Animal Science at the University of California, Davis.
Lead levels in their bloodstream remain high, but would drop quickly if it were not consumed repeatedly, the study says. Fry recommends scanning a feather from each condor using a technique called mass spectroscopy to measure how frequently lead is consumed. That would allow researchers to develop an exposure history for each bird.
A separate study for the U.S. Fish and Wildlife Service found "there is a strong tendency for the toxicity events to occur in the fall of the year, roughly coinciding with hunting seasons," although lead poisoning from ammunition has happened at other times as well.
The federal report was written by a steering committee of hunters, conservation groups, and wildlife conservation agencies.
State wildlife officials tinkered with Fry's report for months, worrying it would draw protests from the hunters Fry estimated leave more than 30,000 dead animals scattered across the condors' range annually.
In releasing the reports, the agencies emphasized their cooperation with hunting organizations and predicted that the majority of hunters would comply with the voluntary guidelines.
The federal steering committee recommended hunters within the condors' range remove or bury carcasses or body parts left after the game is field-dressed; or remove bullets and surrounding affected areas; or use lead-free ammunition.
"We really see hunters as the original conservationists" who will help once they know there is a problem, said Lorna Bernard, a spokeswoman for the state wildlife department.
While Fry's report said officials should consider banning lead bullets and shot within the condors' range, "there is no smoking gun in the report that says, yes, it's lead from ammunition and we're going to have to consider some sort of ban," Bernard said.
Five condors have died of lead poisoning since 1997, including one in California, one in Utah, and three in Arizona. An additional 26 condors have received emergency treatment to reduce toxic lead levels.
Lead bullet or shotgun pellet fragments were confirmed in two of the dead birds. Metal fragments found in two others weren't analyzed to see if they were lead. X-rays spotted dense fragments in three living condors with high lead levels, but those fragments were not removed and analyzed.
"It's certainly a far cry from pointing the finger at hunters, because we just don't know," Bernard said. "There's still a lot of missing links to this puzzle."
Fry noted researchers have rarely found condors eating hunter-shot carrion, even with intense visual surveillance and the use of radio tracking devices.
Lead also could come from natural sources, pollution, shooting ranges, or from residue in calf carcasses used in condor feeding programs. Fry said researchers should take lead samples from deer and other grazers that live within condor habitat to determine how much lead they are ingesting.
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On the Net:
http://www.dfg.ca.gov/hcpb/info/bm--research/bm--pdfrpts/2003--02.pdf
