I heard part of the Halloween edition of This American Life the other day on the drive home, and I thought I would share because it was genuinely freaky, creepy, scary, and absolutely true.
They told the story of this woman who lives in upstate New York who was out for a walk one day when she saw this raccoon. As soon as it saw her, it came charging at her, hissing and spitting, and it just attacked her, relentlessly. She eventually managed to pin it and call her family for help, but it was totally, unwaveringly hostile, and they ended up having to beat it to death with a tire iron. Then there was a separate horror story about her trying to wend her way through a bureaucratic maze to get the vaccine, because of course the raccoon was rabid.
So here's the really scary bit, which is about rabies: rabies is 100% fatal in humans unless you get the vaccine within 72 hours. And the way that it works is that it attacks the aggression centers in the brain. Not only does it make infected creatures violent and aggressive, it also makes them immune to pain. An infected critter sees another critter, and it immediately runs after it to attack it and spread the virus. And there's nothing at all supernatural about any part of this -- it's just how Nature works in this case.
Here's the best part: bats can get rabies, too. If a bat bites you while you're sleeping, not only might it not wake you up, sometimes it won't even leave a mark! So if you find one in a room with someone sleeping, it's important to catch it and get it tested.
[Bats are still very cool and generally do NOT have rabies, though, so don't be getting all paranoid about them.]
Nature is scary sometimes.