Minecraft wiki entry for Summoning_jockeys, associated text: In a nutshell, the passenger will behave regularly if they are mounted on a mob, but they will have a speed boost (equivalent to the players walking speed, or the passenger speed if the Passenger's speed is faster than the players' speed). For example, if you have a wolf mounted on a cow, and you punch the wolf, the wolf will ride the cow towards you and inflict damage, and it will also make nearby wolves (even wolf jockeys) hostile. If a skeleton mounts a mob, it can strafe (as skeletons do when attacking). The only exception are endermen. They will teleport away (with the passenger), if a projectile is shot through them. However, if the enderman is the passenger, it will not teleport away but it cannot be damaged by projectiles.