Posted on behalf of Brendan Borrell
In the latest chapter of a long-running debate over lead bullets, researchers presented the strongest evidence to date that hunting ammo is poisoning endangered California Condors.
Myra Finkelstein, an environmental toxicologist at the University of California at Santa Cruz, and colleagues analyzed lead isotope ratios in 65 birds after their release into the environment and found they fell between 0.81 and 0.83 — within the range of 71 bullet samples, most of which were turned in by hunters in California. Pre-release birds had lower concentrations of lead in their blood, and their isotopic ratios were higher (0.83 to 0.85). In addition, Finkelstein found that sub-lethal concentrations of lead in blood (20 ug/dL), result in a 60% decrease in an enzyme necessary for cellular energy and hemoglobin production. The results were presented yesterday at the Society for Conservation Biology meeting in Edmonton, Canada.
California condors used to soar across the western United States, but by 1982 only 22 remained in the wild. Their captive breeding program is often cited as the most expensive species recover effort in U.S. history, costing up to $2 million per year. Yet today, out of 304 birds released into the wild, 116 of them have died. Half of those deaths are due to lead poisoning, which causes damage the nervous system among other effects. Condors are scavengers and most scientists believe they are being poisoned by feeding on carcasses killed by hunters.
Steve Beissinger, a conservation biologist at the University of California at Berkeley who was not involved in the research said the results were another “smoking gun” that lead bullets are killing condors. “The California condor is a classic example of what happens when you try to return a species to an environment where the factor that caused its decline has not been reversed,” he said.