  geophagy is the practice of eating earth or soil-like substrates such as clay or chalk. it occurs in non-human animals where it may be a normal or abnormal behaviour, and also in humans, most often in rural or preindustrial societies among children and pregnant women.peter abrahams, human geophagy: a review of its distribution, causes, and implications. in h. catherine w. skinner, antony r. berger, geology and health: closing the gap. oxford university press us, 2003, p. 33. isbn 0-19-516204-8 human geophagy may be related to pica, a classified eating disorder in the dsm-iv characterized by abnormal cravings for nonfood items.pica encyclopedia of mental disorders ==in animals==  geophagy is widespread in the animal kingdom. galen, the greek philosopher and physician, was the first to record the use of clay by sick or injured animals in the second century ad. this type of geophagy has been documented in "many species of mammals, birds, reptiles, butterflies and isopods, especially among herbivores."jared m. diamond, "evolutionary biology: dirty eating for healthy living". nature 400, 120-121 (1999) ===in birds=== separate from geophagy, some birds eat small stones and grit (lignophagia) which remain in their gizzards to aid in grinding food. many species of south american parrots have been observed at clay licks, and sulphur-crested cockatoos have been observed ingesting clays in papua new guinea (discover, 1998) as well as in glenbrook in the blue mountains of australia (parrots magazine, 2000). analysis of most soils consumed by wild birds show that they prefer soils with high clay content, often with the smectite and bentonite clay families being well represented. the preference for certain types of clay or soil can lead to unusual feeding behaviour. for example, peruvian amazon rainforest parrots congregate not just at one particular bend of the manu river but at one specific layer of soil which runs hundreds of metres horizontally along that bend. the parrots avoid eating the substrate in layers one metre above or below the preferred layer. these parrots regularly eat seeds and unripe fruits containing alkaloids and other toxins that render them bitter and even lethal. because many of these chemicals become positively charged in the acidic stomach, they bind to clay minerals which have negatively charged cation-exchange sites, and are thereby rendered safe. their 
Cultural_anthropology Eating_behaviors Ethnobiology Ethology Pica_(disorder)