National Geographic

Californian condor not extinct yet, but still regularly poisoned by lead

The image above, which may be the worst photo of a Californian condor ever taken, was the best shot I snapped during a four-hour condor-watching trip in 2010. But even this grainy image is important, for it captures one of the 405 last Californian condors in the world.

Myra Finkelstein from the University of California, Santa Cruz writes that the condor is “a symbol of environmental tragedy and triumph”. The huge bird, with its three-metre wingspan and eerily smooth flight, was once widespread across North America. Between power lines, guns, and pesticides, their population plummeted. The birds were frequently poisoned by lead after scavenging off shot-filled carcasses, and that’s if poachers weren’t filling them with lead shot in a more direct way.

By 1982, there were just 22 Californian condors left in the world, and all of them were in captivity. An intense captive breeding programme began, and it has been an apparent success. There are currently around 400 birds, more than half of which fly free and wild.

But this might be a pyrrhic victory. Finkelstein has now shown that the condor’s fate is far from certain. Even though we have brought it back from the cusp of extinction, its old enemy – lead – is still a major threat. If conservation efforts are scaled back, the condor will disappear once more unless the use of lead-based ammo is severely or completely curtailed.

Scientists track all the free-flying condors with radio and GPS transmitters, and each bird gets a yearly check-up. These tests revealed that every year, more than half of the birds have levels of lead in their blood that exceed the acceptable threshold – currently set at 100 nanograms per millilitre. And every year, around 20 per cent of the birds had so much lead in their blood –450 ng/mL or more—that they were officially suffering from lead poisoning and needed medical care. Between 1997 and 2010, half of the condors were poisoned at least once.

These stats might paint a bleak picture, but things are probably even worse. Lead has a half-life of 13 days in condor blood, so a yearly check-up will grossly underestimate the amounts that condors are exposed to. Feathers preserve a more accurate record. They revealed that the blood samples underestimated the birds’ lead exposure from 1.4 to 14.4 times, and that many birds had been chronically poisoned for at least a month at a time.

Where does the lead come from? The balance of isotopes (versions of an element with different weights) in the condors’ blood provides a valuable clue. In one isolated case, the cocktail of isotopes was a match for lead-based paint used in a tower where the birds were roosting. But in the vast majority of cases, the isotopes pointed the finger at a different source – lead-based ammo. It’s hard to see the birds actually feeding from shot-filled carcasses, but biologists have done so in at least six cases. In all of these, the balance of lead isotopes in their blood was a match for those in the ammo they accidentally swallowed.

California already has some regulations in place to restrict the use of lead ammo in condor habitat, but the blood levels in the birds haven’t fallen in the years since the rules were put into place. Finkelstein also thinks that the measures don’t go far enough. The problem is that condors are long-lived birds that come across a lot of carrion. Even if only 1 in every 200 carcasses contains lead, the condors would be virtually guaranteed to feed off a contaminated body in a given decade.

Without tougher regulation, it’s unlikely that the birds could sustain themselves on their own. Using population simulations, Finkelstein concluded that if the status quo continues, the condor numbers will hold. That’s assuming that the same intensive conservation efforts that go on today will continue – daily monitoring, medical care, and so on. If those efforts are scaled back, and nothing is done about the lead, the birds will plummet towards extinction again. Only if lead exposure is removed do the birds stand a chance of re-establishing themselves without our help.

Many endangered species require so much money and effort to preserve that conservationists are increasingly faced with a hard question: is every species worth saving? And, are some of them beyond hope? The Californian condor clearly isn’t. We’ve done the hard bit, and the birds seem to be capable to taking things from here. But not if they keep on eating poisonous buffets.

Reference: Finkelstein, Doak, George, Burnett, Brandt, Church, Grantham & Smith. 2012. Lead poisoning and the deceptive recovery of the critically endangered California condor. PNAS http://dx.doi.org/10.1073/pnas.1203141109

Image by Christian Mehlführer

There are 5 Comments. Add Yours.

  1. jules
    June 26, 2012

    My one’s almost as good as yours: from Grand Canyon…
    http://julesandjames.blogspot.jp/2011/06/jules-pics-condor.html

    Do you know whether the condors are sustaining their population even with medical care, or are the conservationers still releasing captive bred birds? Reminds me of my friend’s fish tank, which had to be regularly “fed” with new fish in order to keep up the population.

  2. Kathy Orlinsky
    June 26, 2012

    According to the paper, condor chicks are still being released. The authors speculate that without releasing any captive chicks, it would take close to 2000 years to achieve a stable population of condors…and that’s with all the medical interventions that are currently in place. In other words, things are not going well for the California condor.

    I’m writing a post about this article too, but as usual, Ed has scooped me. Oh well.

  3. Robyn
    June 26, 2012

    There are still releases of captive-bred birds, but the some condors are nesting. Some of the nests have to have a fake egg switched in temporarily (various factors can influence this decision, including viability and eggshell thickness). The egg can then be sent to one of the breeding program zoos to hatch safely, while they send back a healthy egg to be put on the nest. Sometimes this is done to have more genetic diversity in the population.

    The releases of captive-bred juveniles also helps with the genetic diversity (biologists often look at the parents and lineage of the birds before deciding where they are to be released). And the captive-bred releases aren’t just for sustaining the population, but to help increase the populations.

    This year I know of at least four successful hatchings in the Big Sur area, and one more that I’m not sure of yet. Two of them were foster eggs, and two are their actual eggs (I can’t recall about the last egg, one of the ones hatched).

    However, at one nest in the Big Sur/Pinnacles area failed this year. Potentially because first the mother had high lead levels and had to be taken to the LA Zoo for treatment while the father tended the egg, and then once she was returned, it was discovered that the father also had high lead levels and had to be taken in, leaving just the mother to tend the egg.

    The problem with the current regulations about use of lead bullets in condor habitat is that people have stores of ammo built up, so they don’t need to buy new ammo — they’d rather use the lead bullets they already have than go out and buy new bullets. And some hunters are of the opinion that other bullets don’t perform as well as lead bullets (whether that’s true or not, I have no idea), and stick to their lead bullets, even when they are in condor habitat.

  4. Ed Yong
    June 26, 2012

    Great details Robyn. Thanks for chipping in.

  5. Luisa
    June 27, 2012

    Late to the party — apologies in advance for the ton o’ links. For those interested:

    I don’t know of any hunter who has written more about the lead ammo controversy than Phillip Loughlin at The Hog Blog. [See his comment on the availability of alternative ammo here: http://magblog.audubon.org/great-debate-over-lead-bullets Here’s Loughlin’s take on the latest news: http://hog-blog.com/once-again-lead-ban-advocates-only-telling-half-the-story/

    And another post of his, from earlier this year: http://hog-blog.com/lead-ban-chronicles-the-sad-state-of-education-about-lead-ammo/

    Here’s non-lead hunter Anthony Prieto’s NY Times op-ed from 2010: https://www.nytimes.com/2010/12/16/opinion/16prieto.html

    And a more recent video from Prieto: http://vimeo.com/37272263

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