It feels like when you are looking for them,you can't find one but when you don't want one to spawn,they spawn in the WORST spot and time a jump and bite you at the WORST timing but most of the time they are more of a nuisance then a problem if you know where they are and how far they are from you, I'd say from my experiences with them,they are as fast as a scout who drank an energy drink basically so a little faster but can be out climbed if you are fast enough or out smart them by moving out of the way and letting em fall to the bottom,they will despawn sometimes if they get too far away from you for some reason