It's pretty hard to hear, it's the best I could get with my cellphone, but if you turn it up and use headphones you should be able to hear it.
I'm pretty sure that this is the sound of a Vixen (female fox) talking to her kits. Each time I heard this sound it was right after almost a peeping sound, the sound of her kit I assume. This would mean that what I was hearing was the sound of kits that were old enough to come out of the den and play, but still young enough that their calls sound like peeps.
This recording was taken just outside of Yosemite on route 140 where I camped last night, next to a river. I went looking for the den in the morning (including crossing the river etc.) and was unable to find it. I'm not a good enough tracker and there was a LOT of background noise in the area, the soil was all either too hard or too soft to hold a really good track, so I couldn't locate a path to follow back.
In any case, if you're curious maybe you can actually hear it. It sounds like a choking noise (it's actually quite a horrendous sound). I was able to get the whole call because I started recording after hearing the "peep" that preceeded it each time.http://www.smalladventures.net/recording-680046973.3gpp