Geophagy, the intentional consumption of soil, has been observed in humans and numerous other animal species. Geophagy has been posited to be adaptive, i.e., consumed soil protects against gastrointestinal distress and/or supplements micronutrients. We conducted a field experiment in the Budongo Forest, Uganda, to investigate geophagic behaviors, including soil preference, the quantity of soil eaten, and competition for access to preferred soils. We placed pairs of artificial tree stumps at two existing geophagy sites. One stump contained soil from the surrounding area, Sonso, that could supplement bioavailable iron. The other stump contained soil from a neighboring community, Waibira, that was richer in clay minerals, which could provide protection from plant secondary compounds. We monitored activity and engagement with the stumps for 10 days using camera traps. After 5 days, we reversed the type of soil that was in the stumps at both sites (i.e., a crossover design). Only Colobus guereza (black-and-white colobus monkeys) interacted with the stumps. These monkeys used visual and olfactory cues to select between the two soils and exclusively ate the clay-rich soil, consuming 9.67 kg of soil over 4.33 h. Our findings lend the greatest plausibility to the protection hypothesis. Additionally, monkeys competed for access to the stumps, and 13% of the videos captured aggression, including pushing, excluding, and chasing other individuals from the experimental stumps. Nine episodes of vigilance and flight behavior were also observed. Given that intentionally ingested soil is a valuable resource that may confer health benefits, geophagy sites should be conserved and protected.

中文翻译：

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在富含铁和富含粘土的土壤之间进行选择：乌干达布东戈森林保护区黑白疣猴的食土野外实验

Geophagy，有意消耗土壤，已在人类和许多其他动物物种中观察到。Geophagy 被认为是适应性的，即消耗的土壤可以防止胃肠道不适和/或补充微量营养素。我们在乌干达布东戈森林进行了一项田间试验，以研究食地行为，包括土壤偏好、土壤被吃掉的数量以及对首选土壤的竞争。我们在两个现有的食土地点放置了成对的人造树桩。一个树桩含有来自周边地区 Sonso 的土壤，可以补充生物可利用的铁。另一个树桩包含来自邻近社区 Waibira 的土壤，该社区富含粘土矿物质，可以保护植物免受次生化合物的侵害。我们使用相机陷阱监测了 10 天的活动和与树桩的接触。5 天后，我们改变了两个地点树桩中的土壤类型（即交叉设计）。只有 Colobus guereza（黑白疣猴）与树桩互动。这些猴子使用视觉和嗅觉线索在两种土壤之间进行选择，只吃富含粘土的土壤，在 4.33 小时内消耗了 9.67 公斤土壤。我们的发现为保护假说提供了最大的合理性。此外，猴子竞争进入树桩，13% 的视频捕捉到了攻击性，包括从实验树桩中推、排除和追赶其他人。还观察到了 9 次警惕和逃跑行为。鉴于有意摄入的土壤是一种可能带来健康益处的宝贵资源，