I have heard that one time before, and it was very recent. I was in some bushes, and it was too dark to see, but a deer caught a sniff of me, or heard me, and I heard a loud snort, sort of high pitched, but not too high. It sounded more challenging like a buck would, and about 3 or 4 seconds later heard another. It FELT like he was warning me to leave his area, because after that second one I was spooked and scrammed lots of fox and coyote areound here. I left those bushes, but stayed in the area..Never heard it again the rest of the 15 minutes I was there. I think he knew he scared me.