title: Bornean orangutan geophagy: analysis of ingested and control soils.
abstract: Geophagy among orangutans is the most poorly documented in contrast to the knowledge of soil-eating practices of other great ape species. Observations of soil consumption by orangutans in the Sungai Wain Forest Preserve (Wanariset) of Borneo are presented, along with physico-mineral-chemical analyses of the ingested soil in an effort to understand what might stimulate the activity. The consumed soils are: light colored, not excessively weathered by normal standards, higher in the clay size fraction relative to controls, and are comprised of a mix of clay minerals without any specificity of 1:1, 2:1 and/or 2:1:1 (Si:Al) species. The geophagic soils contain chlorides below detection limits, effectively eliminating salt as a stimulus. Soil chemical and geochemical analyses confirm that orangutans prefer soils with pH levels near or above 4.0, while controls are consistently lower (pH = 3.5-4.0), a considerable difference in acidity for at least four out of six soils consumed. Geochemical analysis shows Al, Fe and K are high in the consumed vs control samples; higher Al follows from higher clay percentages in the consumed earth. Iron and K may play physiological roles, but Fe is mostly in the ferrous form (Fe(+2)) and may not be readily taken up by the animals. The preferential choice of consumed samples, with pH above 4.0 and higher clay contents, may promote a more beneficial intestinal environment.
authors.affiliation: Quaternary Surveys, 26 Thornhill Ave., Thornhill, ON, L4J 1J4, Canada. arkose41@gmail.com.|Department of Geography, York University, 4700 Keele St., North York, ON, M3J 1P3, Canada. arkose41@gmail.com.
authors.forename: William C
authors.initials: WC
authors.lastname: Mahaney
authors.affiliation: Department of Anthropology, McMaster University, Hamilton, ON, L8S 4K1, Canada. ronhancock@ca.inter.net.
authors.forename: Ronald G V
authors.initials: RG
authors.lastname: Hancock
authors.affiliation: The Research Institute, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada. susanne.aufreiter@utoronto.ca.
authors.forename: Susan
authors.initials: S
authors.lastname: Aufreiter
authors.affiliation: MWM Consulting, 182 Gough Ave., Toronto, ON, M4K 3P1, Canada. michael.milner@sympatico.ca.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Milner
authors.affiliation: Department of Geography, York University, 4700 Keele St., North York, ON, M3J 1P3, Canada. jvoros@explornet.ca.
authors.forename: Joan
authors.initials: J
authors.lastname: Voros
mesh_terms: D000818:Animals; D001893:Borneo; D007214:Indonesia; D010842:Pica; D011148:Pongo pygmaeus / Q000502:physiology*; D012987:Soil / Q000737:chemistry*
chemical_list: D012987:Soil
keywords: Diet and pharmacology; Great ape nutrition; Mineral and chemical composition of geophagic soils; Orangutan geophagy