Are modern cats even that good at killing rats anymore? Haven't we mostly bred cats that have very rarely even seen a rat their entire life?
Rodents are their strong preference, but if bored, they will go after bugs, small birds, lizards... or engage in relentless "murder practice" using pieces of paper or cloth.
This is very different than with dogs, which often have to be trained for specific tasks. Source: lived with 10+ cats (not at the same time).