Wednesday, February 27, 2013

[Ornithology • 2012] Lead poisoning and the deceptive recovery of the critically endangered California condor Gymnogyps californianus

California Condor
Pinnacles National Monument

By ThorsHammer94539 I-Ting Chiang

Endangered species recovery programs seek to restore populations to self-sustaining levels. Nonetheless, many recovering species require continuing management to compensate for persistent threats in their environment. Judging true recovery in the face of this management is often difficult, impeding thorough analysis of the success of conservation programs. We illustrate these challenges with a multidisciplinary study of one of the world’s rarest birds—the California condor (Gymnogyps californianus). California condors were brought to the brink of extinction, in part, because of lead poisoning, and lead poisoning remains a significant threat today. We evaluated individual lead-related health effects, the efficacy of current efforts to prevent lead-caused deaths, and the consequences of any reduction in currently intensive management actions. Our results show that condors in California remain chronically exposed to harmful levels of lead; 30% of the annual blood samples collected from condors indicate lead exposure (blood lead ≥ 200 ng/mL) that causes significant subclinical health effects, measured as>60% inhibition of the heme biosynthetic enzyme δ-aminolevulinic acid dehydratase. Furthermore, each year, ∼20% of free-flying birds have blood lead levels (≥450 ng/mL) that indicate the need for clinical intervention to avert morbidity and mortality. Lead isotopic analysis shows that lead-based ammunition is the principle source of lead poisoning in condors. Finally, population models based on condor demographic data show that the condor’s apparent recovery is solely because of intensive ongoing management, with the only hope of achieving true recovery dependent on the elimination or substantial reduction of lead poisoning rates

Keywords: wildlife, ecotoxicology, hunting, demography, vulture

Myra E. Finkelstein, Daniel F. Doak, Daniel George, Joe Burnett, Joseph Brandt, Molly Church, Jesse Grantham and Donald R. Smith. 2012. Lead poisoning and the deceptive recovery of the critically endangered California condor. PNAS. Doi: 10.1073/pnas.1203141109


California Condors Constantly Suffer From Lead Poisoning

The Humane Society, Audubon California and Defenders of Wildlife are pushing for California to become the first state to ban lead ammunition for all types of hunting to protect California condors and other wild animals.

In 2008, the state banned lead ammunition for hunting in the California condor’s historic range, which runs roughly from Los Angeles to San Jose, but the groups believe that a wider ban is necessary to prevent condors and other birds, such as bald eagles and vultures, from dying as a result of lead poisoning after eating animals that are shot by hunters.

When hunters leave carcasses or gut piles, they may contain lead shot pellets or bullet fragments. Scavengers who pick at the piles can develop lead poisoning, which can cause inability to fly, anemia, blindness, seizures, starvation and death.

“Countless wild animals suffer and die needlessly every year from the continued use of lead ammunition,” said Jennifer Fearing, state director of the Humane Society of the United States. “It is put in the environment and stays there. It’s toxic, and it’s cumulative.”

The California condor population was reduced to 22 birds by 1982, with the last wild condor brought into captivity in 1987. Captive breeding efforts have been very successful since they began in the 1980s and have boosted the population to around 400 birds who are now in the wild and in breeding programs.

Unfortunately, while the population has grown, condors still face the threat of exposure to toxic levels of lead and require a lot interference from people to keep them from disappearing from the landscape yet again. We’re now breeding them, releasing them, recapturing them, treating them for lead poisoning and releasing them again hoping they survive.

Last year a review of more than 1,154 blood samples taken from wild condors and tested between 1997 and 2010 found that 48 percent of the birds had levels of lead in their bodies that would have killed them without treatment in animal hospitals, reports Mercury News.

Some hunters are supportive of the move to ban lead ammunition and are voluntarily making the switch, but the NRA and others are balking at the idea, claiming that this is somehow an attempt to ban hunting altogether and arguing that there is a lack of evidence to support a ban.

However, studies at the University of California, Davis that were funded by the California Department of Fish and Game have found evidence that lead from ammunition often makes its way into carrion-eating birds and that bans on lead ammunition for hunting waterfowl and in condor habitat were effective in reducing lead exposure. An additional study conducted in 2012 matched isotope ratios found in bullets to those found in birds.

“We’re not against hunting,” said Dan Taylor, public policy director for Audubon California. “But hunting is a privilege. For hunting to continue in a state like California it must be done in the most ecologically and sound way possible.”