A mouse can fit through a hole the size of a ballpoint pen.
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A favorite comparison often used by Dr. Bobby Corrigan, noted rodentologist and award-winning pest management consultant, states that if you can put a #2 pencil into a hole, a mouse would be able to get through it as well. Others like to use the dime as an example of the width a mouse can exploit. Basically, we’re talking about a space that is roughly ¼-inch across.
Source: https://www.victorpest.com/articles/how-do-mice-fit-in-such-small-spaces
Tags: Animal Fact Mouse