Finding the corpse

Our cats, Rex and Roxy are tried and true city kitties - never having seen the outdoors except on the way home from PetCo to our apartment. We wondered how they would deal with barn living, assuming they would adjust. Well, that is an understatement! They have gotten in touch with their inner tigers and are loving life here at the barn, running around outside till all hours, rolling around in the sun...and killing, lots of killing. It started with moths and butterflies, soon escalated to chipmunks and mice, and just last week there was a Frog Maiming. We tried to rescue the frog and send him back to the pond for rehabilitation. All seemed well as he valiantly stroked through the lily pads with only his back legs, but alas, the next morning told a more somber tale. Of course, we are ok with them keeping the barn clear or rodents but it is getting a bit alarming. They come in smacking their lips and with a look I've never seen on their faces - something akin to Hannibal Lechter. I hope we stay on their good side.