what to do about outside pets, when coyotes are close?

I have a home with several cast off kitties. They come from a feral cats litters. we captured the feral mother had her vaccinated and spayed. All her kittens we made sure to touch and some are now outside kitties spayed and vaccinated. Where we live coyotes are following deer in this area and since I once lived out west, I know what they sound like. I was just outside and heard them howling in the distance, our yard is fenced in and we have a shed for our outside cats with bedding etc. but coyotes are very crafty. What can I do to help protect the cats, my house already is at full capacity????