Like in the title said is it sin to watch animals being eaten by their prey alive. I kinda find enjoyment and entertainment to watch it. I'm wondering if it's sin.
It's a sin to watch people commit sins, but Animals don't commit a sin when they eat another animal, at least the action of watching it is not a sin.
Some extremist people asked one of the companions (ra) if it was permissible to kill a fly, he became angry at them for asking, since they where killing some of the best people with no problem, yet they hesitated to kill a bug.
So don't worry too much about that, worry more about your relation to people around you.