The rut can make deer unusually aggressive. It appears from this Arizona video that these mule deer are not just aggressively fighting, but the dominant buck looks like he’s been the bully on the block for quite a while.
The caption from the Youtube page describing the attack states: “This is a little footage we picked up by luck while hunting Mule Deer on the Arizona Strip. Shows how brutal life can be in the wild. Just another day in the life of a Muley Buck!”
WARNING: This video is brutal, and hard to watch.