By Bob Ferris
Over the past few years I have had a number of conversations with hunters, scientists, veterinarians and wildlife rehabilitators about lead bullets, fragmentation and how fragments are entering the food chains of raptors and other scavengers (see here). These exchanges have been helpful in sorting out this complicated issue.
"Ninety-four percent of samples of deer killed with lead-based bullets contained fragments, and 90% of 20 offal piles showed fragments: 5 with 0–9 fragments, 5 with 10–100, 5 with 100–199, and 5 showing >200 fragments. In contrast, we counted a total of only 6 fragments in 4 whole deer killed with copper expanding bullets." In Bullet Fragments in Deer Remains: Implications for Lead Exposure in Avian Scavengers
Is there strong evidence this is happening? Yes. Can it be traced specifically to lead bullets? Yes. Is this something that needs to be dealt with? Yes. Are there viable alternatives? Yes. Is there room for respectful and fact-based debate relating to this issue and how specifically to deal with it? Absolutely.
In terms of evidence one only has to go to Google Scholar (where the scientific papers live) and search under the terms “bullet+fragments+wildlife+mortality.” This action will get you 6500 results. If you do the same switching morbidity for mortality, you get 884 results. All of these articles are just dealing with the narrow issue of bullet fragments and not with the much, much broader issue of lead from other sources including lead shot which yields results in the million records range. It is in fact hard to look at this issue without colliding with a mountain of studies.
“Our results confirm that ravens are ingesting lead during the hunting season and are likely exposed to lead from rifle-shot big-game offal piles.” In Blood Lead Levels of Common Ravens With Access to Big-Game Offal
The problem with lead and lead poisoning is much like climate change in that the science is a combination of compelling correlations, limited experimentation and a good deal of scientific triangulation. That it is complicated leads some to doubt and deny the problem.
The whole situation and the actions of certain players reminds me a little of the story of Typhoid Mary. Mary Mallon was an itinerant cook early in the last century who had asymptomatic typhoid—she carried the disease but did not show symptoms. Her existence was discovered by a typhoid investigator who was hired by a wealthy family to find out why typhoid was popping up in New York where it was unlikely to occur–the houses of the rich. The one and obvious commonality found by the investigator was this cook named Mary. When confronted, Mary rejected the idea that she was the source and locked herself in a bathroom refusing to provide urine or stool samples
Hunters and shooters intent on “going to the mattresses” over lead bullets should spend some time with Mary Mallon’s story because it is one of denial and obstinacy leading to a harsher outcome. Folks were willing to work with Mary and there were viable and admittedly less desirable options, but those were still better than her ultimate fate of repeated incarceration.
When you look at the evidence of bullet fragments poisoning wildlife they tend to fall into general categories and operate collectively much like evidence presented in a criminal trial or the epidemiology involved in Mary Mallon’s case. First there are studies that show that animals near shooting ranges and other concentrations of spent bullets have higher levels of lead in their blood (1,2). This essentially demonstrates that environmental presence leads to poisoning.
Then there are studies that show that bullet fragments are present in big game animals killed with lead bullets (1,2). There are similar studies that show that species that eat lead bullet-killed big or small game animals—including humans—have higher levels of lead in their blood (1,2). In addition, there are studies that show that the incidence of lead poisoning increases during deer hunting season (1,2,3).
And to put a punctuation point on it there are even studies (1,2) that examine lead-tainted blood samples from wildlife and are able to determine the sources of that lead by looking at the lead isotopes contained in the blood and matching them with the differing isotope signatures found in objects like fishing weights, lead shot or lead bullet fragments. If the concept of isotopes makes you queasy or uncomfortable, a good example of an isotope is the so-called Carbon-14 used in the carbon dating process. Carbon 14 or radio-carbon has 6 protons, 6 electrons and 8 neutrons rather than the normal 6—these additional neutrons change the atomic number or mass of the atom but do not change its chemical properties.
Now I can appreciate a healthy amount of apprehension from big game hunters and their desire to pull the political equivalent of a Mary Mallon because they see any efforts to control lead bullets in any manner as simply another step in the march to take their guns. But I would urge them to take a deep breath, look at the substantial body of evidence and then become a productive part of the solution. Because there is nothing in these studies that argues for continued tolerance for spraying the landscape with this toxic element and much that argues that its use should be discontinued or seriously curtailed.