Lead Poisoning - Part IV


Commentary by Sanford R. "Sandy" Wilbur

20 January 2015


I had several interesting discussions about condors and lead this past month, triggered in part by two separate press releases that were picked up by newspapers around the country.

The first concerned lead poisoning in the Arizona and Utah condor populations. To quote portions of one version (this from the website of KNAU, Arizona Public Radio, 13 October 2014): "Deadly levels of lead in endangered California condors are at a 10-year low... A collaboration between conservationists and hunters to reduce the use of lead ammunition is responsible for the drop. In the last year, 13 condors were treated for lead exposure, compared to 30 the previous year... The decline in lead-related deaths is being attributed to more hunters using lead-free bullets. For several years, the Arizona Game and Fish Department has offered copper ammunition instead at no charge to those hunting in the condor’s range... (Chris Parish, supervisor of the Arizona-Utah condor work) says in the last year 80 percent of hunters on the Kaibab Plateau voluntarily took part in the lead-free ammunition program."

I doubt anybody with the Arizona-Utah condor project is now ready to say "mission accomplished," as far as lead poisoning is concerned, but I think it is notable that these are very encouraging preliminary results from an entirely voluntary program to control the amount of lead reaching condors from hunting activity.

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The December press release concerning condors and lead in California adopted a very different tone. Most newspapers led with a title something like this one from The Californian (Salinas, California) 4 December 2014: "Threat to local condors pervasive." The primary function of the press release was to tell about a paper published recently in Conservation Biology. The senior author was Terra R. Kelly, an epidemiologist at the Wildlife Health Center in the UC Davis School of Veterinary Medicine. In that paper, the main conclusion was expressed this way: "Lead exposure was a pervasive threat to California condors despite recent regulations limiting lead ammunition use." The "recent regulations" were put in place in 2008 and, although they didn't ban all types of lead ammunition, "regulations on use of lead projectiles for big game and nongame hunting were implemented throughout the condor's range in California." It seems to me that an immediate question should be: why has an entirely voluntary program shown encouraging results, while seven years of a mandatory restriction on lead in hunting ammunition have not resulted in decreased lead levels?

In the Conservation Biology paper and in the resulting press coverage, a number of reasons were put forth for the apparent failure of the lead restrictions in California.

1. "Condor lead levels significantly increased as age and independence from intensive management increased, including increasing time spent away from managed release sites, and decreasing reliance on food provisions. Greater independence among an increasing number of reintroduced condors has therefore elevated the population's risk of lead exposure and limited the effectiveness of lead reduction efforts to date."

Increasing independence among maturing condors was to be expected; in fact, hoped for, in a successful program. To some extent, it has been occurring from the first introductions of condors into the wild, and is not something that has just begun to happen recently. Here's a note from a 2009 paper from the Arizona condor project: "As elsewhere in their current range, the condors are supplied with a clean lead-free supplemental food source of calf carcasses at the release site in Arizona. As condors disperse from the release site, they forage on carcasses of wild animals... Since 2000, the highest frequency of lead exposure in condors has been associated with increased condor movements away from the release site, and the consumption of non-proffered carcasses potentially containing lead." [Sieg, R., K. A. Sullivan, and C. N. Parish. 2009. Voluntary lead reduction efforts within the Arizona range of the California condor. Pages 341-349 in: Ingestion of lead from spent ammunition: implications for wildlife and humans. Boise, Idaho: The Peregrine Fund.]

The Arizona workers believe (like the California people) lead exposure increases as condors mature, yet the voluntary reduction in lead ammunition in Arizona seems like it is overcoming that particular problem. Doesn't it seem odd that a widespread, mandatory restriction (even if not all inclusive or completely enforced) hasn't been able to counteract the effects of increased condor mobility?

2. “It’s no surprise that condor exposure to lead is unchanged after the onset of the lead ammunition ban,” Sorenson (Kelly Sorenson, a co-author of the Conservation Biology paper) said. “The poor availability of non-lead ammunition for some calibers makes it difficult for many hunters to comply with the ban.”

It is a surprise to me that any level of compliance with the lead ammunition ban wouldn't have resulted in some reduction in the possibilities of condors acquiring lead in their food. Furthermore, in the Californian interview, Sorenson "noted, in particular, the dearth of non-lead .22-caliber bullets, a favorite for shooting varmints on ranchland." Such "varmints" make up a very small portion of condor food, so the limited availability of that type of ammunition should have very little impact on lead available to condors. Finally, I have to wonder why Arizona and Utah hunters are able to come up with enough non-lead ammunition to apparently make voluntary compliance both possible and apparently effective in reducing lead availability.

3. “'These regulations that were implemented in 2008 left some exemptions for when lead ammunition could be used to shoot wildlife,' Terra Kelly, an epidemiologist at University of California, Davis, and the study’s lead author, said in an email."

While a correct statement, I wonder why it constitutes an explanation of the apparent failure of the ban to work. The "wildlife" exempted from the original ban were the "varmints" mentioned above, a rather small portion of potential condor food supply. Again, even with the "varmints" left out of the ban, shouldn't we have expected some significant reductions in lead from reductions in the lead-killed big game animals that condors would be expected to find and eat?

4. "Much of the poisoned carrion is on private lands, and there are not enough game wardens to enforce the ban on public lands." This comment in the Californian article was not attributed to anyone in particular, but there are many variations on this theme in the news and in the condor literature. The assertion is that actual compliance with the lead ban is very low, either because there are not enough wardens to enforce the laws or because (more sinisterly) some wardens are choosing not to enforce the ban. The claim of low compliance has been refuted; but whatever the level of compliance, we come to the same question asked above: even with less than full compliance, shouldn't there be some change for the good after this many years? I refer you again to the reported Arizona-Utah experience.

There is also another inconsistency here. In a 2011 report, of which Dr. Kelly was principal author, the following was stated: "A ban on the use of lead ammunition for most hunting activities in the range of the condor in California was implemented in 2008. Monitoring of lead exposure in predatory and scavenging birds is essential for assessing the effectiveness of the lead ammunition ban in reducing lead exposure in these species. In this study, we assessed the effectiveness of the regulation in decreasing blood lead concentration in two avian sentinels, golden eagles and turkey vultures, within the condor range in California. We compared blood lead concentration in golden eagles and turkey vultures prior to the lead ammunition ban and one year following implementation of the ban. Lead exposure in both golden eagles and turkey vultures declined significantly post-ban. Our findings provide evidence that hunter compliance with lead ammunition regulations was sufficient to reduce lead exposure in predatory and scavenging birds at our study." [Kelly, T. R., P. H. Bloom, et al. 2011. Impact of the California lead ammunition ban on reducing lead exposure in golden eagles and turkey vultures. PLoS ONE 6(4):1-8.]

The 2008 lead ammunition restriction should have had very little effect on the food supply of golden eagles or turkey vultures, as it was aimed at big game hunting (which supplies a pretty small percentage of the food of eagles and turkey vultures). Putting that concern aside, we are still left with the question of why, after only a portion of the first year of the ban (when one would have thought that lack of compliance would have been at its highest), the researchers concluded "that hunter compliance with lead ammunition regulations was sufficient to reduce lead exposure in predatory and scavenging birds." And if they felt it was true then, why - after five more years to get both hunters and enforcers used to the new rules - would they feel that compliance wasn't good enough to show any change for the better in condors?

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We often hear comparisons of winning battles and winning a war. Speaking militarily, the United States probably hasn't been involved in winning a War since World War II. Undoubtedly, we have won many individual battles; whether any of them ultimately had a beneficial effect on the world is likely in the eye of the beholder. Strategically, somebody thought that waging every battle was important to winning the War; probably, there were times that the waging was considered more important than the winning.

Bringing the condors to a secure recovery can be considered in terms of either a battle or a war. In either case, the strategies employed should align with the objective. If the ultimate goal of The War on Lead is to keep as much lead as possible from accumulating in the environment - for the benefit of both humans and other life (certainly a worthy objective) - then any restrictions that come about under the name of "condor preservation" are good. But wars are fought on a very different time line than battles. Even if the War on Lead is won (whatever that ultimately means), it will not be in any of our lifetimes. The condors almost certainly don't have that time. As one observer in 1950 summarized the then-current discussion of oil drilling versus condor preservation ("People See Condors," linked above): “Much has been said to indicate that this is a real oil emergency, but, after all, this oil is probably going to be as valuable in fifteen years or fifty years as it is now. It is not so sure that in fifty years we can do anything for the condor.”

If condor recovery is treated merely as one battle in the much bigger War on Lead, then the waging could be important. However, the condors benefit only if their particular battle is won.

The strategies are quite different if the war we are fighting is (to give it a much longer, but more precise name) The War on Lead in the Environment that is Detrimental to Condor Recovery. Certainly, we hope and expect that anything done to remove threats to condor recovery will also contribute to the bigger War on Lead. But, because the condors' needs are immediate, we need to selfishly turn most of our attention away from the big war, and concentrate on what battles look to be most strategic for winning our smaller war.

I don't know if the smaller war (Condors vs. Lead) is being won; I suspect it isn't. I think it isn't being won because I don't think that those working on condor recovery have a clear idea of what they need to do; i.e., what does winning the war look like? Current thought seems to be something like that expressed by Dr. Kelly, in the Californian article cited above:

“Until we can ensure natural food sources are free from lead ammunition for the population, lead poisoning will threaten recovery of naturally sustaining populations of condors in the wild."

If that - natural food sources free from lead ammunition - is the only way that the condor restoration effort can be successful, then I don't think there is much else that can be done. With the Ridley-Tree law in place since 2008, and with the broader ban on lead sporting ammunition enacted by Governor Brown last year, condors can continue to be caught and chelated, and efforts can be made to keep condors only eating the "clean" food they are given. After that, the results depend on time, prayer, crossed fingers, and the work of the game wardens.

* * *

There is a more active alternative available, however. Using my idea about what the condor vs. lead "war" should really be about, an objective would read something like this:

Make sure that the lead found within the current and proposed habitat of condors does not interfere with the condors' ability to develop naturally sustaining populations.

To address that objective, two pieces of vital information are still needed:

1. How much lead can condors (both as individuals and as the building blocks of a population) "stand?" Pronouncements from the 1980s (still being quoted today) that every condor with lead in its blood was a "goner" were clearly untrue. Pronouncements from more recent times that, even if they don't die from lead, lead-infected condors cannot reproduce or maintain other necessary behaviors, are also overstated. The historical record of lead ammunition use in the condor range suggests that, if lead poisoning in condors was as terminal as described, condors would have become extinct during the peak of deer hunting in the condor range in the 1950s.

I am not saying that lead poison won't kill a certain number of condors in the future, nor am I saying that we can be certain that sub-lethal levels of lead won't seriously affect some condor behavior or physiology. What I am saying is that, based on the history of condors and on the results (and non-results) of lead restrictions to date, it appears quite possible that the seriousness of the lead threat to condor recovery has been overstated. This is an easily investigated hypothesis, by designating some of the existing condors as "controls," to be monitored, but not captured for blood sampling or chelation. Comparing the survival and reproductive activity of these controls to the condors undergoing the current rigorous testing, it should not take many years to determine if condors are going to be able to survive long-term in the contaminated environment, or if real recovery is impossible. If they can make it, great; that opens up the possibility of saving a considerable amount of money, of reducing the stress on the birds caused by all the current handling, and of providing a stronger rationale for considering other reintroduction sites. If the adverse effects are great, then there would be clear justification to either continue the high intensity program, or to abandon recovery efforts as ultimately unworkable.

The zoos are having no trouble producing condors - apparently more than can be used in the existing reintroduction programs - so possible loss of some of the control birds would not set back the existing program. It has been suggested that abandoning the current blood test/chelation protocol might be construed by some as inhumane, and there might be roadblocks to approval of such a study. No doubt, that is possible. In getting the initial approvals to take condors into captivity, we had to tackle objections from many quarters, some of them pretty sticky from various socio-political angles. Taking condors into captivity was considered by some to be "inhumane," and there were more than a few who felt that it was better to let the condors live or die in the wild on their own terms, than to manipulate them in captivity. We won approval because we were able to convince the majority of our "publics" - including our politically sensitive government bosses - that we really had exhausted all other possibilities for saving the condors, and that captive propagation was the one last thing left to try. I think we're at that point, again, with the release program, and the field study is the one last thing that can be done to put the recovery program on a scientific basis.

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2. Why isn't the reduction in lead ammunition in California resulting in significant positive changes in lead levels in condors? I think it is because virtually all restrictions to date have been aimed at reducing lead ammunition used by hunters. If deer and/or pig hunting are the source(s) of a major share of the lead found in condors, it seems almost unbelievable that significantly lower lead levels in condor blood are not apparent after this many years of restrictions. That lead levels have not declined, and that lead levels have been shown to be high at all seasons of the year (not just in response to the principal hunting period), seems ample proof that the principal sources of lead poisoning have not yet been discovered and managed.

Livestock and sea lions are more often documented as condor food than are deer and pigs. Livestock are shot regularly by ranchers (euthanasia), poachers, and vandals. Between 1992 and 2009, the Marine Mammal Center amassed records of nearly 500 marine mammals (mostly sea lions) that had been shot. They considered this a very small sample of the actual numbers shot. As livestock shooting is not a hunting activity, and since shooting marine mammals is already illegal, neither source of potential lead is affected by either the regulations existing since 2008, or the more extensive law passed by California in 2013. I find no evidence that the current condor people have been seriously considering either type of shooting as a lead poisoning problem for condors.

As a trained researcher and a "condor expert," it pains me to see this important program going forward without what I consider rather basic scientific information on actual food habits. Be that as it may, if the field experiment I proposed above showed that it isn't really necessary to complete purge lead from the condor environment, then maybe accurate food habits information isn't essential. If, on the other hand, lead really is a serious limiting factor in condor recovery, better knowledge of what condors are eating, and where the lead in their food supply is coming from, seems mandatory for taking any action beyond the current hunting ammunition restrictions.

A "food habits" study of condors would not be easy, but it is certainly far from impossible. From The Koford Years (late 1930s and early 1940s) through the Sibley-Carrier-Wilbur Years (1965-1979), quite a bit was learned just from having a few trained observers in the field, supplemented by a strong, widespread "observer network" of ranchers, rangers, hunters, wardens, wildlife managers, etc., reporting to us. Add to our limited resources of that time the current availability of marked birds, radioed birds, satellite tracking, etc. I guarantee that today a good research supervisor and two or three grad students could find out a lot in a couple of years - and with slight cost, compared to what is currently being spent on tracking condors with no real purpose, trapping, chelation, etc.


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Sanford Wilbur 2021