Earlier work established the utility of coded particles incorporated in baits to identify animals that had recently eaten the material. Using a low-cost commercial product (Glowble), we have extended this technique for practical field use. Laboratory, pen, and field trials were conducted to test formulations and develop methods for positive identification of marked animals under field conditions. The technique allows determination of percentages of animals feeding on bait material and of specific bait sites where individual animals have fed. Our general approach required examination of carcasses to identify marked animals. Low cost, availability of several codes, and simplicity of identifying marked animals are the principle advantages over similar marking techniques.