Rancor are massive beasts, usually kept in pits and used to kill people who are dropped on them. Rancors are born with incredibly long intestines, and have no natural anus. There have been great leaps in advancement of anal corrective surgeries in some Rancor. However, the surgens rarely surviveso there isn't much work being done in that area any more.
When a Rancor reaches its adult size, it begins getting backed up, the more it eats. This makes them incredibly irritable as they aren't able to poo. Most of them spend their entire life trying to go, and it really upsets them when they can't. What is even more upsetting is when some jerk wanders into their cave, decreasing their chances of going even more since Rancor hate trying to go when someone is watching them.
The way they usually deal with a person trying to watch them lay some cable is by eating them. This of course gives them even more to pass, which they simply aren't able to do. Thus, when the next person drops in on them, they are even more angry and pained. It's a vicious cycle.