Why do men howl like apes when they see a woman?

I experienced this for the first time in a TRAIN. I walked in and there were a bunch of guys who just starting howlinggggg and acting like apes. I was literally mortified I thought i walked in a mental hospital. Looking back at it i am wondering if they meant to direct the howls at me and what that meant? Is this a common thing that i am not aware off. It was honestly embarrassing and offensive.
Why do men howl like apes when they see a woman?
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