Deeper voices are scarier to almost any animal, and humans as well. Most male mammals have deep voices to scare off any predators.

Male mammals are generally larger then their female counterparts, and so are their vocal cords. So when a human or animal hears a deep voice they think, 'male', and males are dangerous. For instance, men have about 10 times the murder rate as women.

So men have deeper voices because they have larger vocal cords. Women's voices are about twice the pitch of mens'.

Women have a very nice mechanism that can prevent violence: they can scream very loudly. And men are programmed to respond to a screaming woman.

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Generally speaking, if you are out in the wild and some large animal looks like it might attack, my non-professional advice is to stand still, raise your hands above your head, and start yelling and cursing at the animal.