The coyotes DO take the mice, chipmunks, rats, etc, etc - as far as the rats - that may be one of the reasons I'm seeing rats this year. There has been a dramatic increase in the coyote population. The coyotes will come in close but not where the yard light shines. The rats are coming in close to get away from the coyotes.
Whatever - four rats in 36+ years isn't that bad. And I just continue to set, check, empty and rebait the traps. Been that way for 36 years - isn't about to change. For every mouse, rat, chipmunk I trap there are probably several out there in the buck brush just waiting their turn. Just a part of country living.