R. G. V. Hancock

Geochemistry and clay mineralogy of termite mound soil and the role of geophagy in chimpanzees of the Mahale Mountains, Tanzania

Earth from a termite mound in the Mahale Mountains National Park, Tanzania, eaten by chimpanzees, was analyzed to determine the possible stimulus, or stimuli, for geophagy. The termite mound sample contains relatively high aluminum (10.0%), iron (3.0%), and sodium (0.5%). This correlates well with the mineralogy of the clay (<2 µm) fraction, which is high in metahalloysite, a 1:1 (Si:Al=1:1) clay mineral similar in chemical composition to the clay mineral kaolinite, and smectite (montmorillonite), which is a 2:1 expandable clay mineral. The combination of metahalloysite and smectite produces a substance much like the pharmaceutical Kaopectate™ widely used by humans as an anti-diarrheal agent. These analyses and preliminary observations linking geophagy with instances of severe diarrhea, and other signs of gastrointestinal upset in the Mahale chimpanzees, suggest that one function for the ingestion of this substance by chimpanzees may be to help provide temporary relief from gastrointestinal ailments. Further detailed investigations into the relationship between health and geophagy should provide important insights into the diverse roles of this behavior as a form of self-medication.

Mineral and chemical analyses of soils eaten by humans in Indonesia.

Five Javanese soil samples, including three earths eaten by humans as therapeutic medicine, were analyzed for their physical, mineral and chemical properties along with suitable control samples (not eaten). The eaten soils have a high content of hydrated halloysite and kaolinite, that is, clay minerals that are pseudoforms of the pharmaceutical Kaopectate™. Along with hydrated halloysite in a ratio of nearly 1:1, the expandable clay mineral smectite is also present, but in much greater quantity than is usually found in Kaopectate™. Among the chemical elements that may act as a stimulus for geophagy, only Na, Mn, K and S are possible candidates driving this behavior. Sodium is inherent in the minerals derived from the volcanic bedrock; and it is present in a form other than NaCl. Iron, which is often higher in soils eaten by both human and nonhuman primates, and has therefore been regarded in the past as a possible stimulus for geophagy, is relatively high in these soils, but does not have a higher concentration in the eaten soils relative to the uneaten soils in this group of samples. Cobalt and chromium, two important trace elements in human nutrition and diet, are marginally but not markedly higher in the eaten samples. The eaten soils in all cases have predominantly higher levels of 1:1 clay minerals than the 2:1 minerals which may predominate in some of the control soils, which some studies have associated with health problems. Soils can adsorb dietary toxins, present in the plant diet or those produced by microorganisms. Taking the toxic alkaloids quinine, atropine, sparteine, and lupanine as examples, it is evident that soils from Ampo (southern Java) have a very good adsorptive capacity, comparable to that of coal or charcoal. Other Javanese soils also adsorb these toxins, but to a lesser degree.

Geophagia by mountain gorillas (Gorilla gorilla beringei) in the Virunga Mountains, Rwanda

Mountain gorillas (Gorilla gorilla beringei) occasionally eat material from weathered regolith (subsoil) sediments in the Virunga Mountains of northwestern Rwanda. The possible nutritional significance of this behaviour has been investigated by analyzing the geochemistry, primary mineral composition, and clay content of several regolith and surface soil (paleosol) samples. Iron, Na, and Br content may be important in geophagy, and clay present in the soil may also have nutritional importance.

Neutron activation analysis of bulk and selected trace elements in bones using a low flux SLOWPOKE reactor.

The mineral phase of bone is a reservoir for some biologically important ions and is the place where some toxic elements are also stored. For these reasons it is important to measure accurately and nondestructively the chemical content of bone, with respect to its main elements (Ca, P, Mg, Na) and its trace elements. We have analyzed different types of human bone by instrumental neutron activation analysis (INAA), using a SLOWPOKE reactor. We have compared our results with inductively coupled plasma emission spectroscopy (ICPES), and we have determined the limits of detection and sensitivity for the various elements, especially some biologically or toxicologically significant trace elements. Finally, we have given two examples of the use of INAA in following the penetration of an element (F) with time into bone and in characterizing nondestructively the mineral content of bone biopsies of a rare pathological condition (osteopetrosis).

Chemistry, mineralogy and microbiology of termite mound soil eaten by the chimpanzees of the Mahale Mountains, Western Tanzania

Subsamples of termite mound soil used by chimpanzees for geophagy, and topsoil never ingested by them, from the forest floor in the Mahale Mountains National Park, Tanzania, were analysed to determine the possible stimulus or stimuli for geophagy. The ingested samples have a dominant clay texture equivalent to a claystone, whereas the control samples are predominantly sandy clay loam or sandy loam, which indicates that particle size plays a significant role in soil selection for this behaviour. One potential function of the clays is to bind and adsorb toxins. Although both termite mound and control samples have similar alkaloid-binding capacities, they are in every case very high, with the majority of the samples being above 80%. The clay size material (<2 μm) contains metahalloysite and halloysite, the latter a hydrated aluminosilicate (Al 2 Si 2 O 4 -nH 2 O), present in the majority of both the termite mound soil and control soil samples. Metahalloysite, one of the principal ingredients found in the pharmaceutical Kaopectate is used to treat minor gastric ailments in humans. The soils commonly ingested could also function as antacids, as over half had pH values between 7.2 and 8.6. The mean concentrations of the majority of elements measured were greater in the termite mound soils than in the control soils. The termite mound soils had more filamentous bacteria, whereas the control soils contained greater numbers of unicellular bacteria and fungi.

Mountain gorilla geophagy: A possible seasonal behavior for dealing with the effects of dietary changes

Geophageous Rwandan mountain gorillas excavate and eat weathered leucite-rich regolith (subsoil C horizons) from the slopes of Mount Visoke in the Virunga Mountains. In the months of the dry season, the gorillas reportedly ingest a halloysitic natural earth having a chemical composition similar to that of Kaopectate, a pharmaceutical used by humans to treat gastrointestinal upsets. Several plants known to contain potential toxins are consumed more heavily by gorillas in these months. New information from geochemical and mineral analyses suggests that geophagy may alleviate intestinal problems associated with changes in their diet because the ingested weathered regolith,containing halloysitic clay minerals, may act as a pharmaceutical agent that helps to adsorb toxins and to control dehydration in the dry season.

Energy-dispersive X-ray microanalysis of the bone mineral content in human trabecular bone: A comparison with ICPES and neutron activation analysis

To evaluate the accuracy of bone mineral composition determination by electron microprobe analysis (EDX) the measurements have been compared to instrumental neutron activation analysis (INAA) and chemical analysis (ICPES). Bone specimens from five femoral heads were used. The trabecular content of calcium (Ca) and phosphorus (P) was analyzed by the three different methods. The FDX method allows for a microstructural analysis of intact, methylmetacrylate-embedded, undecalcified bone and the measuring points can thus be distinctly identified centrally in each trabecula. The analysis yielded 25.8±0.7 wt% Ca and 10.5±0.1 wt % P, compared with 22.2±0.5 and 23.0±1.0 wt % Ca, and 9.83±0.21 and 10.02±0.44 wt % P for INAA and ICPES, respectively. The EDX analysis was calibrated by consecutive measurements of a hard, pressed tablet of hydroxyapatit of known content. The mean Ca content deviated with-0.38 wt % from the given content and P with-0.89 wt %. We could not verify any particular interference from the embedding procedure, however, it is possible that the relatively lower P content still may reflect this. The magnesium (Mg) concentration was 0.31±0.02 wt % by EDX and 0.26±0.02 wt % by INAA. The EDX analytical method provides a useful tool for simultaneous elemental quantification in bone. It has the advantage of permitting the use of cation bone biopsy material and thus allowing for a unique microstructural evaluation of the degree of mineralization. By comparison with other established methods, the assessment of accuracy and reliability indicates that the measurements are well in range for the major constituents, Ca and P, whereas INAA is more sensitive in determining trace elements.

Analysis of geophagy soils in Kibale Forest, Uganda

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 Kaopectate™. Among the elements that may act as a stimulus or stimuli for geophagy behavior, only iron is very high (total iron ranges from 6% 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™. Organic chemical analyses indicate only traces of organic matter and no humic acids in the K14-E14 sample.

Geochemistry and clay mineralogy of soils eaten by Japanese macaques

Three groups of soils from two Japanese monkey parks at Arashiyama (Honshu) and Takasakiyama (Kyushu) were analyzed for their geochemistry and clay and primary mineral content. Two groups (Y and T) of soils are regularly eaten by Japanese macaques; a third group (N) is not eaten. Of the elements analyzed, soil group N (not eaten) is within the range of all elements in the Y group, and is very different from the T group. These preliminary data suggest there is no chemical stimulus in soil eating behaviour. We also analyzed the mineralogy of the clay fraction (<2 µm) but could find only a possible stimulus from ingesting plagioclase and orthoclase minerals. The clay mineral content consists of small to trace amounts of metahalloysite that might play a role in countering the effects of diarrhea. However, from the available data there are no clear trends that would provide a stimulus for geophagic behaviour.

Geophagy amongst rhesus macaques on Cayo Santiago, Puerto Rico

Soil mining and eating (geophagy) behavior of rhesus macaques (Macaca mulatta) on Cayo Santiago, Puerto Rico, is described and assessed with respect to the chemical, geochemical, and mineralogical composition of the ingested materials. The samples forming the uneaten (control) and eaten (matrix and blocky) groups of soils come from the top and flanks of a marine terrace underlain with volcanic tuff on Cayo Santiago, off the east shore of Puerto Rico. Both the uneaten and geophagy samples were analyzed to determine particle size distributions, clay and primary mineralogy, and soil chemical and geochemical compositions. Primary minerals such as orthoclase and plagioclase feldspar in the clay fraction is higher in the control group than in the ingested samples. Both the control and matrix plus blocky samples have moderate to abundant amounts of kaolinite and halloysite (both silicon:aluminum = 1:1 type clay minerals) that may be important as a stimulus to geophagy behavior. The pH, total salts, and phosphorus levels in both the control and geophagy samples show considerable overlap with little clear indication of causal factors. Analysis of the geochemical data showed no clear cut elemental differences to suggest elemental supplementation as a possible explanation for mining and eating of tropical soil. It is possible that rhesus macaques ingest clay to obtain kaolinite/halloysite minerals which may alter the taste of their provided food, and may act as pharmaceutical agents to alleviate intestinal ailments such as diarrhea.