>WATCH: Kingsnake receives assistance after attempting to devour itself
>That snake is retarded.
They do this when under distress due to being too hot. It's a combination of confusion and disorientation from the heat and an accelerated metabolism caused by the rise in body temperature, which causes them to feel hungry and attempt to eat the first thing they see. Since it's not typical for food to just be laying around a snake's cage, the first thing they see is probably going to be their own tail.
It is a sad thing that happens from neglectful ownership, in other words.