Upland game differs both environmentally and physiologically from waterfowl. Upland game habitat is broader and is not concentrated over one particular area. Consequently, upland game hunting areas typically do not have places where lead shot tends to accumulate like it does in certain waterfowl hunting areas. Additionally, lead is not readily soluble in soil. Upland game, specifically upland birds, are more particular in their feeding preferences and will not select lead shot preferentially over food (seeds, plant matter, etc.) when foraging. Also, in the unlikely event that an upland bird mistakenly consumes a piece of shot, the food consumed by the animal will stimulate the digestive process such that the bolus of food is rapidly passed out of the stomach before any significant amount of lead can be absorbed. The ingestion of food buffers stomach acid and greatly reduces its already minimal ability to dissolve metallic lead. Further, the ingestion of food causes the stomach to rapidly process its contents and to quickly expel those contents into the intestinal tract, where complete neutralization of the acid is accomplished. Once in the neutral conditions of the intestinal tract, there is no plausible mechanism whereby metallic lead can be absorbed by the organism. Thus, decreased exposure time in the stomach due to the presence of food makes dissolution of metallic lead extremely unlikely to lead to poisoning of wildlife or humans. In a study directly on point, researchers attempted to poison turkey vultures by continuously feeding six turkey vultures large amounts of lead shot with food. When the birds excreted the shot, the researchers cleaned and re-administered the shot to the birds, with the goal of determining the amount of time necessary for a turkey vulture to succumb to lead poisoning. After 211 days of being continuously fed significant amounts of metallic lead in their food, four of the six turkey vultures in the study showed few signs of lead poisoning. Only when very large amounts of lead were continuously administered for 143 days were the researchers able to induce a fatal lead poisoning in two of the six turkey vultures in the experiment. This experiment clearly shows how difficult it is for wildlife to be poisoned by food containing lead ammunition.