Shitters

That's rat or possum crap. Rabbit poo looks like cocoa puffs.
I've had a possum get in my dart when I had the steering column out, and got trapped in the car when I reinstalled the column, and then my valiant had a possum die in the back seat after crawling in through the rusted out floor boards. Possums love mopars, at least mine, it seems.

In any case, poison it, break its neck, or camp out with a .22. If you're not careful you'll find some bum living under there soon enough.

Especially if it's a slant 6 car.