Kurt K. Burnham

Bullet Fragments in Deer Remains: Implications for Lead Exposure in Avian Scavengers

Abstract Bullet fragments in rifle-killed deer (Odocoileus spp.) carrion have been implicated as agents of lead intoxication and death in bald eagles (Haliaeetus leucocephalus), golden eagles (Aquila chrysaetos), California condors (Gymnogyps californianus), and other avian scavengers. Deer offal piles are present and available to scavengers in autumn, and the degree of exposure depends upon incidence, abundance, and distribution of fragments per offal pile and carcass lost to wounding. In radiographs of selected portions of the remains of 38 deer supplied by cooperating, licensed hunters in 2002–2004, we found metal fragments broadly distributed along wound channels. 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. These findings suggest a high potential for scavenger exposure to lead.

Lead bullet fragments in venison from rifle-killed deer: potential for human dietary exposure.

Human consumers of wildlife killed with lead ammunition may be exposed to health risks associated with lead ingestion. This hypothesis is based on published studies showing elevated blood lead concentrations in subsistence hunter populations, retention of ammunition residues in the tissues of hunter-killed animals, and systemic, cognitive, and behavioral disorders associated with human lead body burdens once considered safe. Our objective was to determine the incidence and bioavailability of lead bullet fragments in hunter-killed venison, a widely-eaten food among hunters and their families. We radiographed 30 eviscerated carcasses of White-tailed Deer (Odocoileus virginianus) shot by hunters with standard lead-core, copper-jacketed bullets under normal hunting conditions. All carcasses showed metal fragments (geometric mean = 136 fragments, range = 15–409) and widespread fragment dispersion. We took each carcass to a separate meat processor and fluoroscopically scanned the resulting meat packages; fluoroscopy revealed metal fragments in the ground meat packages of 24 (80%) of the 30 deer; 32% of 234 ground meat packages contained at least one fragment. Fragments were identified as lead by ICP in 93% of 27 samples. Isotope ratios of lead in meat matched the ratios of bullets, and differed from background lead in bone. We fed fragment-containing venison to four pigs to test bioavailability; four controls received venison without fragments from the same deer. Mean blood lead concentrations in pigs peaked at 2.29 µg/dL (maximum 3.8 µg/dL) 2 days following ingestion of fragment-containing venison, significantly higher than the 0.63 µg/dL averaged by controls. We conclude that people risk exposure to bioavailable lead from bullet fragments when they eat venison from deer killed with standard lead-based rifle bullets and processed under normal procedures. At risk in the U.S. are some ten million hunters, their families, and low-income beneficiaries of venison donations.

Genetic structure among continental and island populations of gyrfalcons

Little is known about the possible influence that past glacial events have had on the phylogeography and population structure of avian predators in the Arctic and sub‐Arctic. In this study, we use microsatellite and mitochondrial control region DNA variation to investigate the population genetic structure of gyrfalcons (Falco rusticolus) throughout a large portion of their circumpolar distribution. In most locations sampled, the mtDNA data revealed little geographic structure; however, five out of eight mtDNA haplotypes were unique to a particular geographic area (Greenland, Iceland, or Alaska) and the Iceland population differed from others based on haplotype frequency differences (FST). With the microsatellite results, significant population structure (FST, principal components analysis, and cluster analysis) was observed identifying Greenland and Iceland as separate populations, while Norway, Alaska and Canada were identified as a single population consistent with contemporary gene flow across Russia. Within Greenland, differing levels of gene flow between western and eastern sampling locations was indicated with apparent asymmetric dispersal in western Greenland from north to south. This dispersal bias is in agreement with the distribution of plumage colour variants with white gyrfalcons in much higher proportion in northern Greenland. Lastly, because the mtDNA control region sequence differed by only one to four nucleotides from a common haplotype among all gyrfalcons, we infer that the observed microsatellite population genetic structure has developed since the last glacial maximum. This conclusion is further supported by our finding that a closely related species, the saker falcon (Falco cherrug), has greater genetic heterogeneity, including mtDNA haplotypes differing by 1–16 nucleotide substitutions from a common gyrfalcon haplotype. This is consistent with gyrfalcons having expanded rapidly from a single glacial‐age refugium to their current circumpolar distribution. Additional sampling of gyrfalcons from Fennoscandia and Russia throughout Siberia is necessary to test putative gene flow between Norway and Alaska and Canada as suggested by this study.

Genetics of Plumage Color in the Gyrfalcon (Falco rusticolus): Analysis of the Melanocortin-1 Receptor Gene

Genetic variation at the melanocortin-1 receptor (MC1R) gene is correlated with melanin color variation in a few reported vertebrates. In Gyrfalcon (Falco rusticolus), plumage color variation exists throughout their arctic and subarctic circumpolar distribution, from white to gray and almost black. Multiple color variants do exist within the majority of populations; however, a few areas (e.g., northern Greenland and Iceland) possess a single color variant. Here, we show that the white/melanic color pattern observed in Gyrfalcons is explained by allelic variation at MC1R. Six nucleotide substitutions in MC1R resulted in 9 alleles that differed in geographic frequency with at least 2 MC1R alleles observed in almost all sampled populations in Greenland, Iceland, Canada, and Alaska. In north Greenland, where white Gyrfalcons predominate, a single MC1R allele was observed at high frequency (>98%), whereas in Iceland, where only gray Gyrfalcons are known to breed, 7 alleles were observed. Of the 6 nucleotide substitutions, 3 resulted in amino acid substitutions, one of which (Val(128)Ile) was perfectly associated with the white/melanic polymorphism. Furthermore, the degree of melanism was correlated with number of MC1R variant alleles, with silver Gyrfalcons all heterozygous and the majority of dark gray individuals homozygous (Ile(128)). These results provide strong support that MC1R is associated with plumage color in this species.

The Use of Genetics for the Management of a Recovering Population: Temporal Assessment of Migratory Peregrine Falcons in North America

Background Our ability to monitor populations or species that were once threatened or endangered and in the process of recovery is enhanced by using genetic methods to assess overall population stability and size over time. This can be accomplished most directly by obtaining genetic measures from temporally-spaced samples that reflect the overall stability of the population as given by changes in genetic diversity levels (allelic richness and heterozygosity), degree of population differentiation (F ST and D EST), and effective population size (N e). The primary goal of any recovery effort is to produce a long-term self-sustaining population, and these genetic measures provide a metric by which we can gauge our progress and help make important management decisions. Methodology/Principal Findings The peregrine falcon in North America (Falco peregrinus tundrius and anatum) was delisted in 1994 and 1999, respectively, and its abundance will be monitored by the species Recovery Team every three years until 2015. Although the United States Fish and Wildlife Service makes a distinction between tundrius and anatum subspecies, our genetic results based on eleven microsatellite loci suggest limited differentiation that can be attributed to an isolation by distance relationship and warrant no delineation of these two subspecies in its northern latitudinal distribution from Alaska through Canada into Greenland. Using temporal samples collected at Padre Island, Texas during migration (seven temporal time periods between 1985–2007), no significant differences in genetic diversity or significant population differentiation in allele frequencies between time periods were observed and were indistinguishable from those obtained from tundrius/anatum breeding locations throughout their northern distribution. Estimates of harmonic mean N e were variable and imprecise, but always greater than 500 when employing multiple temporal genetic methods. Conclusions/Significance These results, including those from simulations to assess the power of each method to estimate N e, suggest a stable or growing population, which is consistent with ongoing field-based monitoring surveys. Therefore, historic and continuing efforts to prevent the extinction of the peregrine falcon in North America appear successful with no indication of recent decline, at least from the northern latitude range-wide perspective. The results also further highlight the importance of archiving samples and their use for continual assessment of population recovery and long-term viability.