Lead poisoning is a major factor limiting the success of efforts to rebuild populations of the endangered California condor. Since the mid-1980s, condors have been bred in captivity and released back into the wild in California, Arizona, and Baja California. The birds, which feed on carrion, can ingest lead from ammunition in animal carcasses or gut piles left behind by hunters.
The UCSC researchers used a "fingerprinting" technique based on the unique isotope ratios found in different sources of lead. The technique enabled them to match the lead in blood samples from condors to the lead in ammunition. Their findings were published online today by the journal Environmental Science & Technology.
"There had been anecdotal reports for years about condors being exposed to lead from ammunition, but there was never enough clear evidence to document the extent of the problem. We knew that we could probably identify the sources of the lead using isotopic signatures," said Donald Smith, professor and chair of environmental toxicology at UCSC and a coauthor of the paper.
The study was spearheaded by Smith's graduate student, Molly Church, who is now at the University of Pennsylvania's School of Veterinary Medicine and is first author of the paper. Church worked with researchers at several institutions and organizations, including the Ventana Wildlife Society and the U.S. Fish and Wildlife Service, to collect and analyze blood and tissue samples from California condors. She also analyzed ammunition obtained from a variety of sources throughout central California.
"We sampled the ammunition that these birds are most likely to encounter in the remains of hunted game, and we found that lead from those sources can account for the lead in the blood of 77 percent of the birds tested," said Church, who undertook the study after spending a summer monitoring condors as a volunteer with the Ventana Wildlife Society.
The researchers obtained blood samples from 18 free-flying condors in central California and 8 birds that had been raised in captivity and were still in holding pens waiting to be released. At the time of the study, this sample represented 43 percent of the wild condor population in all of California.
The lead levels in the blood of prerelease condors were low, and the lead was isotopically similar to background lead in the California environment. In the free-flying condors, however, blood lead levels were higher and the lead had a different isotopic composition that approached the composition of the lead in ammunition. In the most severely lead-poisoned birds, the blood lead matched exactly the composition of the lead in ammunition, Smith said.
"We found that in the birds with elevated blood lead, the lead isotope ratios fit a mixing model in which one source of lead is the background environment and the other source is ammunition. The results show that lead ammunition in animals shot and left in the field is the predominant source of lead exposure in condors," he said.
Kelly Sorenson, executive director of the Ventana Wildlife Society, said the study provides a solid basis for efforts to resolve the problem of lead exposure in condors. Possible solutions range from legislation limiting the use of lead ammunition to voluntary programs to encourage the use of alternative ammunition in areas where condors are known to scavenge for food, he said.
"There are different ways to get at this problem, but no matter how it is resolved in California, this research was desperately needed not only to confirm the source of the lead but to demonstrate the extent to which ammunition is contributing to the problem," Sorenson said.
In another part of the study, the researchers showed that feathers can be used to monitor lead exposure in condors. They analyzed lead in tissue samples and a feather from a condor that had died of lead poisoning in Arizona. They found that the feather, sampled sequentially along its length, provided a record of the bird's history of lead exposure.
"This shows that we can use feathers to look at the history of lead exposure in individual condors, and we're just starting to do that now with birds that have been reintroduced in California," Smith said.
The elevated lead levels in reintroduced condors are cause for concern even when they are below the level that would cause death from acute lead poisoning, he added. Although it is very difficult to evaluate sublethal effects of toxic substances in wild animals, he said, lead is well known to cause neurological problems in vertebrate animals at relatively low levels of exposure.
"The lead levels that we commonly see in condors are well above the levels considered a concern for human health. If we saw those levels in children, they'd be diagnosed as lead-poisoned and medically treated," Smith said.
Church said she hopes the findings prompt greater efforts not only to reduce lead exposure in condors but to reduce lead contamination in California in general.
"Lead is a well-known toxin that should no longer be getting into the environment, and it would truly be a shame if lead poisoning negated the significant condor conservation efforts and achievements that have taken place over the past several decades," she said.
Tim Stephens | EurekAlert!
Successful calculation of human and natural influence on cloud formation
04.11.2016 | Goethe-Universität Frankfurt am Main
Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Life Sciences
08.12.2016 | Physics and Astronomy
08.12.2016 | Materials Sciences