[ HEALTH ]
What Lead Leaves Behind
As scavengers, vultures rely on leftovers that
hunters, both animal and human, leave behind.
And when they feed on carcasses or gut-piles of
animals that were killed with lead bullets, they’re
potentially being exposed to high concentrations
of lead. An analysis of the bones of turkey and
black vultures, culled at random from flocks
around Richmond, Virginia, found chronically high
lead levels that indicated long-term and repeated
exposure. The consistency of the result surprised
“I’ve never, in 20 years of research, been able
to make a statement that 100 percent of my study
subjects did anything,” said wildlife biologist Todd
Katzner, who supervised the work published in the
scientific journal Environment International. Lead
exposure, he stated, “is clearly a fact of life for
birds that spend a lot of time scavenging.”
Lead mimics aspects of calcium in its chemical
structure, so it’s incorporated, like calcium, into
the nervous system and bones of birds as well
as humans. The lead that found its way into the
vultures Katzner’s team looked at had a chemical
signature consistent with the lead used to make
bullets and shotgun pellets, though the researchers
couldn’t rule out other factors.
Other studies put a finer point on things.
A review of three decades of research recently
published in the The Condor, an ornithology
journal, concluded that ingesting lead ammunition
and fishing tackle is directly linked to illness and
death in more than 120 different bird species.Among
some species, like turkeys and black vultures, most
individual animals appear to survive the exposure.
For others – such as eagles, California condors,
and loons – a significant percentage do not.
The findings have led to renewed calls to ban
lead ammunition. Mark Pokras, a veterinarian and
researcher from Tufts University, testified during
a hearing held by the Vermont state legislature
in May 2015. “I can categorically state that lead
toxicosis from ingestion of hunting ammunition
is a serious problem for wildlife in Vermont and
the rest of New England,” he told the House Fish,
Wildlife and Water Resources Committee, which
was considering a bill that would ban the use of
lead bullets for hunting.
Opponents argue that such a ban is unnecessary.
“Traditional ammunition has never been proven
to have a species population-level impact on
wildlife,” wrote Jake McGuigan, director of
state affairs for the Connecticut-based National
Shooting Sports Foundation, in his testimony
to Vermont lawmakers. In short, members of
the group agree that individual birds are some-
times poisoned by swallowing lead shot or
fragments of bullets left behind in piles of offal and
other remains, but they don’t see evidence that
lead is hampering bird populations as a whole,
particularly in the context of other threats, including
predation from domestic cats and the loss of
habitat from development. Currently, the Vermont
bill and a similar one under review at the Rhode
Island statehouse are being held back from floor
votes pending further study.
In Connecticut, New Hampshire, and New York,
fish and wildlife departments have taken an edu-
cational rather than legislative approach, providing
information on their websites about alternatives to
lead bullets. Copper and copper-alloy bullets are
now available in many popular ammunition sizes,
particularly those used to hunt large game. They
tend to be more expensive than lead bullets, but
the performance of copper bullets has been favor-
ably reviewed by those who use them. In educating
the public, these agencies go beyond the effect
that lead has on animals to emphasize the toll
that ingesting lead can have on human health. In
particular, many studies have tied high blood lead
levels in young children to developmental delays.
New Hampshire’s Fish and Game Department
warns that even the most carefully dressed meat
from animals shot with lead bullets may contain
fragments too small to notice. “Lead particles in
game meat are a concern,” it says. Pregnant or
nursing women and children younger than six
“should minimize or avoid consumption of venison
harvested with lead ammunition.” That said,
adults who eat venison infrequently are unlikely
to be at risk.
Many wildlife managers and researchers
believe that tapping into hunters’ long-standing
concern with wildlife conservation and animal
welfare may be the best way to encourage a
voluntary switch to non-lead ammunition.
Lead from bullet fragments left behind in carcasses shows up in the systems of scavengers.