Lead exposure in California Condors threaten Population Growth

California Condor - Credit: U.S. Geological Survey, Department of the Interior/USGS, U.S. Geological Survey/photo by Susan Haig - PD

(Best Syndication News) - A study from the University of California, Santa Cruz, found that condors in the state are being exposed to detrimental lead levels, which is slowing the repopulation of the endangered species. On June 25, the researchers published their study results in the online early edition of the Proceedings of the National Academy of Sciences (PNAS).

The primary source for lead exposure comes from lead found in ammunition. The researchers determined this based on a “fingerprinting” technique of isotopes. Additionally, they studied the lead levels in the birds’ feathers to understand the history of lead exposure.

First author Myra Finkelstein, a research toxicologist at UC Santa Cruz, expressed concern by saying the cost and time for managing the lead poisoning problem in the condor population will be intense. She continued to explain that the condors are tagged and monitored. The scientists catch the birds bi-annually and test for lead poisoning. If the bird has lead poisoning, they are treated at a veterinary hospital. Some birds die because they are not treated soon enough.

The reason that the birds are at a higher risk for lead contamination is that they are scavengers that could eat a carcass that contains lead bullets or pellets. They may ingest the bullets and this can cause the lead poisoning. The researchers suggest that lead poisoning may have been one of many ways that was pushing the species to extinction.

In 2008, there was a partial ban implemented in California for the use of lead ammunition where condors live. The ban has since been expanded. Even though the bans are in place, the researchers did not see a decline in lead levels in the condors’ blood. Finkelstein explained that even if a couple of people use lead ammunition when hunting, this could cause lead contamination in a number of condors.

The California condor was at the verge of becoming extinct in 1982 when it was estimated that only 22 birds comprised the entire population. A captive breeding program was used to increase the wild population, and by 2010, the population grew to around 400 birds (both captive and free).

The new study suggests that around half of all wild living condors have needed lead poisoning treatment since 1997. On a yearly basis, around one in five of the birds will need to be treated. The treatment involves chelation therapy to remove the excessive lead in the bird’s body. Once they have returned to adequate health, the birds are then returned back to the wild.

Not all condors tested are at the lethal level. Every year, around 30 percent of the condors have lead levels that can cause sub-lethal health effects.

In the next several decades, the condor population could dwindle back down to the 1982 numbers if no additional intervention is done, according to the researhers.

However, the wild condor population is currently stable, but only if there is intensive management efforts by humans. Study co-author, Jesse Grantham, who recently retired as head of the condor recovery program for the U.S. Fish and Wildlife Service, said that the government agency spends around $5 million yearly towards saving the California condors. In order to keep the population from declining, this level of intervention and spending by the government is needed the researchers said.

By: Julie Marcus
Science and Technology Writer

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