(Source: famouswhy.com)

(Source: famouswhy.com)

During the summer months, mice will generally live outside and remain contended there. But as soon as the weather begins to cool, they seek the warmth of our homes. Because of their soft skulls and gnawing ability, a hole the size of a ballpoint pen (6mm – 1/4 inch) is large enough for them to enter en masse. Once inside, they will constantly gnaw at virtually anything – including concrete, lead, and plastic. This is to keep their ever-growing teeth at a convenient length. Contrary to popular belief, mice don’t generally like cheese – but will eat it on occasion. Mice can jump up to 46cm (18 inches), swim, and travel vertically or upside-down. To mouse proof your house, check all small openings with a ballpoint pen – if it fits the hole, it will let mice in.

source: http://listverse.com/2009/01/03/10-weird-and-wonderful-oddities-of-nature/