ESTIMATES OF SOIL INGESTION BY WILDLIFE

Many wildlife species ingest soil while feeding, but ingestion rates a re known for only a few species. Knowing ingestion rates may be import ant for studies of environmental contaminants. Wildlife may ingest soi l deliberately, or incidentally, when they ingest soil-laden forage or animals that contain soil. We fed white-footed mice (Peromyscus leuco pus) diets containing 0-15% soil to relate the dietary soil content to the acid-insoluble ash content of scat collected from the mice. The r elation was described by an equation that required estimates of the pe rcent acid-insoluble ash content of the diet, digestibility of the die t, and mineral content of soil. We collected scat from 28 wildlife spe cies by capturing animals, searching appropriate habitats for scat, or removing material from the intestines of animals collected for other purposes. We measured the acid-insoluble ash content of the scat and e stimated the soil content of the diets by using the soil-ingestion equ ation. Soil ingestion estimates should be considered only approximate because they depend on estimated rather than measured digestibility va lues and because animals collected from local populations at one time of the year may not represent the species as a whole. Sandpipers (Cali dris spp.), which probe or peck for invertebrates in mud or shallow wa ter, consumed sediments at a rate of 7-30% of their diets. Nine-banded armadillo (Dasypus novemcinctus, soil = 17% of diet), American woodco ck (Scolopax minor, 10%), and raccoon (Procyon lotor, 9%) had high rat es of soil ingestion, presumably because they ate soil organisms. Biso n (Bison bison, 7%), black-tailed prairie dog (Cynomys ludovicianus, 8 %), and Canada geese (Branta canadensis, 8%) consumed soil at the high est rates among the herbivores studied, and various browsers studied c onsumed little soil. Box turtle (Terrapene carolina, 4%), opossum (Did elphis virginiana, 5%), red fox (Vulpes vulpes, 3%), and wild turkey ( Meleagris gallopavo, 9%) consumed soil at intermediate rates. Ingested soil may be the principal means of exposure to some environmental con taminants or the principal source of certain minerals. Soil-ingestion estimates may be required for risk assessments of wildlife inhabiting contaminated sites and for computing budgets of those nutrients associ ated mainly with soil.