Many people have claimed that squirrels have "charged" them.  Even seeming to chase you.  Do they have rabies?  Or some disease that makes them do this?  Or that they have had baby squirrels come right up to them, unafraid.  Are these the results of squirrels becoming more aggressive? No, of course not. First of all, baby squirrels are born without any fear of humans (or anything) and they can often be attracted to any movement, especially when they're not with their nestmates. I've had them climb up my jeans and cuddle in the warmth from my hand. The squirrels that "charge" you, or seem aggressive aren't doing that to scare or attack you. These are squirrels that usually associate humans with food, generally because they've been hand-fed over a period of time. (You can easily train an urban squirrel to take a peanut out of your hand within 3 days, if you try and know how to do it.)  The charging squirrels will always stop short of you, or a threatening move on your part will discourage them. RABID ANIMALS However, a rabid mammal (of any kind) often does unexpected things, sometimes attacking even inanimate objects, so associating with (or feeding) ANY wild animal is a definite no-no. The reason for the "boldness" you see is the direct result of the interface between urban squirrels and the human habitat. As scavengers, they are USED to people and will seek to investigate any cooperating human. A note of caution handling animals, wild or domestic. ALWAYS wash your hands in hot, soapy water after handling these critters and either wash or dispose of any gloves you use to do the same.