...but I know what it is. :)
A FOX!
A fox in heat. Have you ever heard a fox in heat? It's pretty terrifying, at least until you figure out what the hell it is. You'd never guess something so relatively small can make that much noise.
She is kinda cute, though.
Her screams obviously are working… 
Oh, that reminds me of a joke, that I cannot tell here.
You want scary? Try the scream of a Bobcat. Makes the hair on your head, (and various other places
), stand on end and makes you want to not be standing in the middle of a forest with several of them around.
I hear tell the scream of a panther sounds like a woman’s dying screams, you’d swear it was a human being tortured the way I hear it told. Nice time to have some serious illumination handy!
What does the fox say?
Shine a light at it.
The first time I heard one I had the same reaction. Makes for a uneasy feeling when you hear one and its pitch black dark outside. 
Olympus LS-10?
Galaxy SII video > audio extracted via avidemux > mp3directcut = fox.mp3
Bobcat, although it's not the mating scream, but it gives you an idea.
Bobcat/Cougar/Panther scream, sounds more like the bobcats that used to scream in our front yard in the spring mating season. We used to watch them every year.
When it's dark enough that you can't see your hand in front of your face. it's a real wake up call.
I’ve heard this before. Now I know it’s foxes!
Doesn’t sound like mating sound but territory control to me.
Nope, it's mating. It's the right time of year, and I've seen her boyfriend out there too (and she is not very nice to him!).
This video has one doing the other call, it's different: http://www.youtube.com/watch?v=zBpZTo1dlPM
Watch for the neat trick with the ears - I guess if I were able to make a noise like that I would want to be able to rotate my ears in the opposite direction, too, lol.
f#ck the fox, and let’s get back to flashlights 
loooooool J)
you need a hunting light and more for this red devil |(
Very cool stuff.
first time I ever heard a fox holler. I was in a tree stand, in Flat, Texas. Judging by the sound it produced, I thought I was fixin’ to find out what Sasquatch looked like! Seconds later, here comes Mr. Fox trotting across in front of me. I think I literally lol’ed at that one.
Steve
While we’re on the subject, a lynx sounds exactly like a human baby crying. Creeps you out pretty bad when you’re out in the bush, miles from anybody.
The last thing I heard screaming in my yard was one of the old ladies here, screaming at her deaf husband. It was pretty scary too!