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IP:5.188.*.* 于 2017-03-11 15:58 评论道：
This is surely possible in three steps:1. (Male) narwhals have elongated upper incisors (their tusks).2. Elephants also have tusks. Young elephants – like the young of many species – eat the faeces of adults to obtain the specific bacteria required to seed their gut to enable digestion of vegetation. Eating faeces is known medically as pica (an appetite for substances largely nonu-ntritive).3. Pica sounds rather similar to pika!
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