New findings out of UCSC shed light on lead poisoning among condors
Almost all of the 100 free-flying condors in California have suffered from severe lead poisoning at least once. Treatment is expensive and stressful for the birds, as they must be removed from the wild and sent to zoos and veterinary hospitals. After re-release, many get sick again and find themselves back in captivity.
Now, researchers from UC Santa Cruz have confirmed that lead ammunition is the most plausible source of exposure, and demonstrated that lead causes chronic, long-term effects as well as acute poisonings. The findings were presented at the March 6 – 10 annual Society of Toxicology meeting in Washington D.C., and may help spark conversation about a more stringent lead bullet ban.
Myra Finkelstein and her colleagues from UCSC analyzed 70 blood samples taken from 49 condors. Using a technique called lead isotopic composition analysis, the researchers identified the chemical fingerprint of the lead found in condor blood. They compared this to the lead signatures of 71 different ammunition samples—most collected in the field.
The researchers found that 90 percent of the birds had blood lead signatures within the same range as that of the bullets. The remaining birds had an a-typical exposure source, while a few had not been exposed to lead.
“For over 100 years we have known condors can be poisoned when they eat carcasses shot with lead bullets, although facets of the hunting lobby remain unconvinced,” says Finkelstein. “Our findings help refute some of their claims.”
In a 2009 letter to the California Department of Fish and Game, National Rifle Association’s Susan Recce argued that lead ammunition cannot be linked to high blood lead levels in condors. “There was no proof of that linkage and, therefore, no expectation that banning the use of lead ammunition will reduce health risks to condors,” she wrote.
Others have suggested that trash is a potential source
of lead, and that ammunition shouldn’t be blamed for condor poisonings.
Finkelstein’s new findings paint a different picture. Not only did the lead in condor blood match ammunition samples, it revealed that the contaminant has a larger impact than previously thought.
Even at low levels, Finkelstein found that lead inhibits an important enzyme responsible for making red blood cells called ALAD. Even in condors with relatively low blood lead levels, the enzyme’s activity was inhibited by 60 percent.
“When lead poisoning doesn’t send the birds in for veterinary care, it can still cause chronic, long-term, sub-lethal effects,” she says.
Graham Chisholm, executive director of Audubon California, says these findings should not go ignored. "The findings provide further proof linking lead ammunition to the poisoning of California Condors,” says Chisholm, who was not affiliated with the study. “While condors still face an uphill fight, hunters can make a difference by using non-lead ammunition.”
Banning Lead Bullets
The findings may breathe new life into a poorly enforced lead bullet ban. In 2007, Gov. Arnold Schwarzenegger signed the Ridley-Tree Condor Preservation Act (AB 821) into law. The bill went into effect July 1, 2008, banning the use of lead bullets within condor territory.
As natural predators like grizzly bears and wolves are driven to near-extinction, hunter-shot carcasses are a major source of food for condors, which must scavenge, as they cannot kill their own prey. Deer and elk sometimes escape hunting parties to die in the forest. This means the animal, and the lead bullets in it, will remain behind.
Gut piles left when an animal is cleaned can also contain microscopic bits of lead. X-rays show that when a lead bullet hits an animal, a snowstorm of lead particles spreads far from the impact site. In 2006, Washington State University researchers found lead fragments in 18 of 20 gut piles tested. Most had between 10 and 200 fragments, although five gut piles exceeded this. In contrast, only six fragments were found in four whole deer killed with copper bullets.
Since the implementation of AB 821 in California, a lack of funding has meant scant enforcement, which, in turn, has led to poor compliance. In Big Sur—one of the state’s three condor release sites—most birds are brought in with blood lead levels 10 times higher than would impair a human.
“It’s not that they are particularly sensitive to lead. Condors are relatively tolerant to it. The problem is that they are constantly exposed,” says Joe Burnett, senior biologist at the Salinas, Calif.-based Ventana Wildlife Society. It only takes one contaminated carcass to poison a flock.
Historically, condors were also poached for museum exhibits and killed by ranchers. The birds once spanned an area from British Columbia to Baja Mexico, and inland to Utah, Idaho and parts of Texas. It was along the Monterey Bay that Spanish explorer Antonio de la Ascension made the first western documentation of condors in 1602 when he spotted the birds feasting on a beached whale. Yet by 1982 there were only 22 condors left in the wild. All were taken into captivity for breeding.
While condors can no longer be found around the Monterey Bay, about 50 birds have been released down the coast in Big Sur since 1997. Together with a sister site in Pinnacles National Monument in San Benito County, and another at the Ventura County-based Hopper Mountain National Wildlife Refuge, 167 condors have been released California. Sixty-one of these have died. Many of the survivors have an ongoing need for treatment due to lead poisoning.
“If we want the condors to have a sustainable free flying population, we need to better regulate the use of lead ammunition,” says Finkelstein.
Until lead is removed from the forests and grasslands where condors feed, the U.S. Fish and Wildlife Service, which authorizes reintroductions, will not approve new releases. Even though new birds will be released into existing flocks, no new release stations are likely to be approved, and the population is not likely to expand north of the Golden Gate Bridge and up the coast.
“It’s our policy not to introduce birds into areas where they might come into contact with lead, through ammunition or otherwise,” says Jesse Grantham, condor program coordinator at the U.S. Fish and Wildlife Service. He clarifies there is no formal written document that spells out such a practice, and no official policy on the requirement of lead reduction at potential new release sites.
The Yurok Tribe hopes to begin releasing condors along the North Coast by 2013, near the mouth of the Klamath River in Del Norte County. Yet, due to its avid hunting community, the North Coast is also full of lead ammunition.
This past winter, the Yurok launched “Hunters as Stewards”—a program that encourages reductions in lead ammunition. The tribe is setting up shooting ranges where lead-free bullets can be tested, and organizing an ammunition exchange where lead bullets can be traded for other alternatives.
The Yurok will also buy a portable x-ray machine to use at meat processing facilities where hunters bring their carcasses for preparation. “We will be asking hunters if we can x-ray their carcasses to show how far lead fragments stray from the wound site,” says Chris West, a wildlife biologist for the Yurok Tribe. Humans can also be exposed to lead particles when they eat lead-shot meat.
West hopes the Tribe’s efforts will set a new course for the birds. “Humans are the ones who brought the problem to the condors,” he says. “It’s not like there is a natural extinction going on, and it’s up to us to repair the damage that has been done.”
written by Jeff McLoughlin, April 01, 2011
|< Prev||Next >|