The domestic horse () makes dung deposits to form “stud-piles” and compulsively examines dung droppings, suggesting that dung contains species-relevant information. The present study investigates horses’ use of location (place), odor (object) and memory for dung sniff encounters. Horses were video recorded in 2 indoor and 4 outdoor riding arenas as they were taken at different time intervals to experimenter-determined objects or dung deposits that they could sniff. Frame-by-frame video analysis measured approaches, sniff duration, nostril use, ear position and blinking associated with dung investigation. Horses approached and sniffed dung-deposits for longer duration than non-dung objects in all test locations. They made head movements across the extent of dung-deposits when sniffing, showed no nostril or ear preference directed to the target, and blinked as they disengage from sniffing. Reduced approach probability and sniff duration showed that they displayed good place/object memory for dung previously visited at similar and different locations on the same day but poor memory for dung visited on a previous day. Adaptive forgetting of object/place memory for dung after a previous day’s dung visit may optimizes risk assessment, including the possibility of premature interruption of foraging by conspecifics.

中文翻译：

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家马（Equus ferus caballus）粪便的地点/物体记忆的适应性遗忘：一天的记忆

家养的马将粪便沉积成“马匹堆”，并强迫性地检查粪便，这表明粪便中含有物种相关信息。本研究调查了马在闻粪便时对位置（地点）、气味（物体）和记忆的使用情况。在 2 个室内和 4 个室外骑马场中，马匹在不同的时间间隔被带到实验者确定的它们可以嗅到的物体或粪便沉积物处，并进行了视频记录。逐帧视频分析测量了与粪便调查相关的接近、嗅闻持续时间、鼻孔使用、耳朵位置和眨眼。在所有测试地点，马匹接近并嗅探粪便沉积物的时间比接近非粪便物体的时间更长。它们在嗅探时会在粪便沉积物范围内移动头部，没有表现出鼻孔或耳朵对目标的偏好，并且在停止嗅探时会眨眼。降低的接近概率和嗅探持续时间表明，它们对同一天在相似和不同位置访问过的粪便表现出良好的位置/物体记忆，但对前一天访问过的粪便表现出较差的记忆。在前一天的粪便访问后，对粪便的物体/地点记忆的适应性遗忘可能会优化风险评估，包括同种动物过早中断觅食的可能性。