Animals on the 4th of July

We have a doggie door, the girls can be inside or outside, whatever they choose.... Mostly they've been outside since the temps are in the 70's... But there have been a few explosions that have caused they to come inside... But they are surprisingly calm when they do decide to come in.... My last two Huskies the male acted just like these two, the female would curl up under my office desk, under my feet... She wouldn't normally ever do that but when big fireworks were going off thats where you'd find her...
I've always wondered........What keeps the raccoons and beavers from coming in through the doggie door?