An unknown, neighborhood cat showed up in my yard today. He was clearly examining the situation. He looks well fed but I am still suspicious since I lost my dear RIR Duchess to an unknown predator [which clearly had claws, could be a racoon or opossum...] but I'm still worried. They are free run and while I am usually home and always put them away at sundown, this is the first time I've seen a cat stalking in the mid-afternoon. Should I be concerned, and what can I do to prevent besides letting my Catahoula [dog] chase him away?