Geophagy (Clay licks and colpas)

Geophagy – whats it all about? Alan Lee Geophagy is defined as the intentional consumption of soil, and has been recorded in a variety of taxa including mammals, birds, reptiles and insects. There are several different theories to explain the act of geophagy in vertebrates, including: (1) adsorption of toxic plant compounds onto clay particles and gastrointestinal protection (2) mineral supplementation (3) the clay minerals in the soil possibly alleviating stomach upset or relieving diarrhea (4) mechanical enhancement of digestion. Different animals may consume clay or soil for different reasons and possibly obtain multiple benefits by doing so. Geophagy has been well documented among mammals. Geophagy amongst humans has attracted a lot of attention but no clearly identified single cause for the behaviour has been identified: iron has been highlighted as important; it is used to counteract intestinal problems; and there may be various benefits for pregnant women, including calcium supplementation. The most recent studies conclude that gastrointestinal adsorption is the most plausible function of human geophagy, that allows greater exploitation of marginal plant foods and reduced energetic costs of diarrhoea – which could account for the high frequency of geophagy in children and pregnant women across the tropics. Apart from humans, geophagy has been recorded in many other primates including gorillas and chimpanzees, as well as a host of other mammals from ungulates to carnivores. Another recent study from Tanzania suggest that licks in the Ngorongoro Conservation Area, provide supplemental sodium, but that selenium, cobalt and molybdenum at the largest licks provide easily overlooked nutritional benefits and are perhaps the primary target for geophagy, using the taste of salt as a clue for locating such zones, although sodium acquisition explains geophagy in a range of organisms from butterflies to babirusas. Availability of dietary sodium is clearly a driving factor causing geophagy in Zimbabwe for African elephants Loxodanta africana, especially females, although soil consumption by elephants might help to minimize the toxic effects of plant secondary compounds in forest browse in other locations. A study of natural licks used by peccaries Tayassu spp. in Brazil showed levels of sodium at least as high as sites in Peru also used by peccaries and other mammals from Tambopata clay licks. Avian Geophagy Geophagy in birds has been increasingly described in the literature in the recent years from all the continents except Antarctica. Prominent families include the Psittacidae (Parrots), Cracidae (Guans), Columbidae (Pigeons), Turacidae (Turacos or loeries), Bucerotidae (Hornbills) and Corvidae (Crows). Although most commonly reported from the tropics, Rosy-faced Lovebirds Agapornis roseicollis have even been recorded regularly eating soil in desert-like environments. The main hypotheses for geophagy in birds are (1) the neutralization of toxic and/or digestion inhibiting plant secondary compounds contained in many tropical fruits and seeds. (2) Essential minerals and elements may also be important for some species, and some species, like cassowaries, may simply be attracted to the colours of the soils in question. Studies from the Tambopata Macaw Project show that parrots choose geophagy sites with higher concentrations of sodium, and even in temperate climates sodium supplements are visited by a variety of garden birds. Records of geophagy by parrots from around the world are becoming well reported. Geophagy in psittaciforms is well recorded where large flocks of parrots visit claylicks in the Neotropics to ingest soil. However, avian geophagy could be more common than literature records suggest and is a topic with various unanswered questions. Some popular literature aimed at the economically important group of tourists looking for birds overlooks or gives a false impression of the abundance of avian clay licks. Wheatley’s “Where to watch birds in South America” (1995) only mentions salt licks in passing in relation to Manu Wildlife Centre, while the section on Tambopata does not receive any mention. Valqui’s “Where to Watch Birds in Peru” (2004) mentions clay licks at the following sites: Blanquillo, Cocha Cashu, Pantiacolla, Posada Amazonas, Tambopata Research Centre and Heath Wildlife Centre in the department of Madre-de-Dios, and only one, Pucani, in the department of Junin. Clements and Shany (2001) state that “many Neotropical parrots visit “clay” licks (colpas) along streams and banks, but the nutritious value of this supplement is still in doubt”, but give no indication of which species are involved or where these sites can be located. However, clay licks appear to be common in Peru, more so than any other country, and their importance to the tourism industry has not been given the spotlight they deserve. Only a few lodges in Ecuador offer visits to salt licks and none are as spectacular as the ones in Peru.