First time I ever herd it was in 1983, I was hunting a rub line were a bean and corn field met,when a 170 class Buck comes in, makes a scrape, rubs 2 new trees, then walks over and stands 15 yards inside the wood line with the outline of his body broken up by a bush. By this time I was a reck, (not being able to get a shot at him because of limbs). The Buck stood there for probably 10 minutes only raising and lowering his head to get a better view of the bean field when something caught his attention. I looked up to see a smaller, younger buck chasing a doe around about 200 yards away, When the Big Buck let out the loudest, long,URRRRRRP I had ever herd, and took off after the buck and doe in the field at a gate, grunting every other step 5 times, and chased them back into the corn field!4 other times I have herd the "GROWL", 3 were about the same as the first, (Aggressive behavior) except the one last year. My wife had spine shot a buck and when we went back to get it, it was still alive. I had her get in front of the buck to get its attenhion, then I grabed it by the horns ( this is when it "GROWLED")gave it a twist, then threw my body weight on it and broke its neck. I found that werd, but guess itwould alsobe considerd aggressive behavior!