Suicidal Squirrels

While biking the past couple of weeks or so, I've noticed that the squirrels around here have gone nuts! Sorry about that... Anyway, usually I don't have to worry too much about them running across my path, but it seems that lately they have all decided that they should at all costs try and get under my front tire. What's the deal? Are they all so preoccupied with the collective task of storing food that they aren't noticing me until the last second? Hitting a squirrel at 20+ mph is not something I want to experience...