海角大神

California聽condors, one of the world鈥檚 most endangered species, are poisoned by聽lead聽from hunters鈥� bullets 鈥渁t epidemic levels,鈥� and will not recover unless more is done to prevent it, a study released Monday concluded.

A review of more than 1,154 blood samples taken from wild California聽condors聽and tested from 1997 to 2010 found that 48 percent of the birds had聽lead聽levels so high, they could have died without treatment.

So far, a ban on聽lead聽bullets in the birds鈥� habitat appears to have had little effect, the study found.

鈥淟ead聽poisoning is preventing the recovery of California聽condors,鈥� said Myra Finkelstein, a research toxicologist at the University of California, Santa Cruz, who was a聽lead聽author of the study. 鈥淭he population is not self-sustaining.鈥�

Condors聽鈥� the birds with the largest wingspan in North America 鈥� are scavengers. They eat dead deer, pigs and other animals, often that hunters have shot. They ingest bullet fragments and are poisoned.

California Gov. Arnold Schwarzenegger signed a law in 2007 to ban hunting with聽lead聽bullets, slugs or buckshot in the聽condors鈥� range, which extends from Los Angeles to San Jose, where the birds have been seen atop Mount Hamilton. But it hasn鈥檛 worked. Birds analyzed before the law took effect had blood levels the same as birds analyzed afterward.

The reason, said Finkelstein, is that a聽condor聽eat 75 to 150 dead animals a year.

鈥淚f just one has a聽lead聽bullet fragment, that can be enough to kill the bird,鈥� she said.

Condors聽once ranged from British Columbia to Mexico. But because of habitat loss, hunting and聽lead聽poisoning, the population dwindled to just 22 nationwide by 1982.

Federal biologists captured all remaining wild聽condors聽in 1987 and began breeding them in zoos. The birds鈥� offspring have been gradually released back to the wild.

Today the California聽condor聽population has grown to 386. Of those, 213 live in the wild at Big Sur, Pinnacles National Monument in San Benito County, Southern California, Arizona, Utah and Mexico. The other 173condors聽live in captivity, at places such as the Los Angeles Zoo.

Although the population growth has been impressive, it is deceptive because it is highly dependent upon human intervention, the researchers said in Monday鈥檚 study, which was published in the Proceedings of the National Academy of Sciences.

Every free-flying聽condor聽has a radio or GPS collar to track it. Nearly all of them are captured twice a year and tested for聽lead. A few chicks have been born in the wild, but biologists still put out out food, such as stillborn calves, for the birds to eat so their population can have a chance to grow.

Monday鈥檚 study, which also looked at聽lead聽levels in聽condor聽feathers, confirmed that聽lead聽in the birds is coming from bullets, rather than other sources such as old paint chips, by matching isotope levels of聽lead聽in bullets tolead聽in the聽condors.

Researchers were surprised, Finkelstein said, by the extensive poisoning.

For example, 30 percent of all聽condors聽captured every year have聽lead聽levels that, while not potentially fatal, can block reproduction and cause immune system problems.

And 20 percent of the birds captured every year have levels that could kill them if not treated with chelation, a process where聽condors聽are fed calcium-based drugs that bind to the聽lead聽and help them pass it naturally. But the process also strips nutrients, and can cause the birds to be hospitalized a month or more.

In California, the state Department of Fish and Game and some hunting and environmental groups have worked to promote the聽lead聽ban in聽condor聽habitat. Some surveys show high compliance rates. But there is little enforcement, and ranchers or hunters can still use聽lead聽bullets and shot, which are cheaper and more readily available than other types of ammunition, such as copper, with little risk of getting caught.

Tthe Center for Biological Diversity, an environmental group based in Tucson, Ariz., and six other conservation groups sued the U.S. Environmental Protection Agency this month to force the agency to institute controls or bans on聽lead聽ammunition.

鈥淲e鈥檝e removed toxic聽lead聽from gasoline, paint and most products exposing humans to聽lead聽poisoning, now it鈥檚 time to do the same for hunting ammunition to protect America鈥檚 wildlife,鈥� said Jeff Miller, a spokesman for the Center for Biological Diversity.