For a long time biologists believed that male deer used buck rubs not only to clean and polish antlers but also to provide practice for the ensuing male-to-male combat during the rut.
长期以来，生物学家们认为雄鹿擦痕不仅可以清除并磨光鹿茸，还可以借此练习发情期时雄鹿之间的角斗。
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In what they are calling a major advance, the scientists found the drug, Truvada, could help to dramatically curb male-to-male HIV transmission.
The researchers focused on men, they said, because prior research has suggested that face-width-to-height ration is "particularly important" in male-to-male interactions.