Analysis of geophagy soils in Kibale Forest, Uganda

Abstract

ABSTRACT. Four soil samples from the Kibale Forest, Uganda, representative of material regularly ingested by chimpanzees, were studied for their mineral, chemical, and geochemical composition. These geophagy soils have a high content of metahalloysite, a partially hydrated clay mineral that may act much like the pharmaceutical KaopectatC M. Among the elements that may act as a stimulus or stimuli for geophagy behavior, only iron is very high (total iron ranges from 60/o to 17%); other possibilities such as calcium, chromium, cobalt, bromine, and iodine are either relatively low or are below their detection limits. Chlorine is below detection limits which eliminates sodium chloride as a possible stimulus. Depending on relative availability in the gut, iron offers the most likely chemical stimulus for geophagy and given the mineral composition of the samples, metahalloysite is the most likely mineral stimulus. Iron may play a role in replenishing hemoglobin which would be important in chimpanzee physiology at high elevations near the flanks of the Ruwenzori Mountains. Metahalloysite, which in this case exists in a relatively pure crystalline form, may well act to quell symptoms of diarrhea and act similarly to Kaopectate TM. Organic chemical analyses indicate only traces of organic matter and no humic acids in the K14-E14 sample.

Visitations by Snowshoe Hares (<em>Lepus americanus</em>) to and Possible Geophagy of Materials from an Iron-Rich Excavation in North-Central British Columbia

“…animals at high altitude (>2500 m) may have an increased need for iron to replenish hemoglobin due to increased oxygen demand (Mahaney et al 1997), but that does not provide a plausible explanation for soil ingestion in this location.…”

“…We did not detect elevated iron levels in Prickly Rose and therefore do not ascribe the increased iron levels in fecal pellets to this source. Mahaney et al (1997) found that 0.15-0.20% of iron in soils consumed by chimpanzees could be extracted with an acid of the same pH as that of the digestive tract, making it a bioavailable iron. Iron in soils could therefore be an important nutritional source for Snowshoe Hares.…”

Ecological importance of licks to four ungulate species in north-central British Columbia.

“…Many pre-treatments of soil material also may affect results by destroying and preventing detection of potentially important clay minerals (Kabata-Pendias and Pendias 1992). Very few studies have selected a pH for extraction solutions that is similar to the pH of absorption sites in the digestive tract (e.g., Mahaney et al 1997). …”

Adaptive function of soil consumption: anin vitrostudy modeling the human stomach and small intestine

“…Moreover, mineral nutrients are usually sufficient in an animal's routine diet (Hladik and Gueguen, 1974;Gilardi et al, 1999); and, among primates, elements are similar between unconsumed soils and those consumed selectively and repeatedly (Izawa, 1993;Mahaney et al, 1995;Müller et al, 1997;Bolton et al, 1998). Furthermore, in soils consumed by chimpanzees, only Fe was present in high concentrations (range 6-17%; Mahaney et al, 1997). However, available Fe was only partially soluble in conditions modeling the chimpanzee stomach (oxalic acid at pH 2.0), indicating it was an improbable cue.…”

“…Accordingly, Kaopectate ® and Smecta ® are common commercial products featuring, respectively, kaolinite and smectite, clays that assuage diarrhoea in monkeys and humans (Beck et al, 1977;Leber, 1988;Guarino et al, 2002). Compellingly, humans report consuming soil expressly to relieve diarrhoea, and kaolinite is usually, but not always, the principle clay fraction ingested by humans and nonhuman primates (Vermeer and Ferrell, 1985;Aufreiter et al, 1997;Mahaney et al, 1997Mahaney et al, , 2000Knezevich, 1998). Of course, both adsorptive functions are not mutually exclusive.…”